File: INSTALL

package info (click to toggle)
perl 5.24.1-3+deb9u5
  • links: PTS, VCS
  • area: main
  • in suites: stretch
  • size: 103,716 kB
  • sloc: perl: 559,611; ansic: 293,886; sh: 67,316; pascal: 7,632; cpp: 3,895; makefile: 2,436; xml: 2,410; yacc: 989; sed: 6; lisp: 1
file content (2712 lines) | stat: -rw-r--r-- 106,774 bytes parent folder | download
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
1837
1838
1839
1840
1841
1842
1843
1844
1845
1846
1847
1848
1849
1850
1851
1852
1853
1854
1855
1856
1857
1858
1859
1860
1861
1862
1863
1864
1865
1866
1867
1868
1869
1870
1871
1872
1873
1874
1875
1876
1877
1878
1879
1880
1881
1882
1883
1884
1885
1886
1887
1888
1889
1890
1891
1892
1893
1894
1895
1896
1897
1898
1899
1900
1901
1902
1903
1904
1905
1906
1907
1908
1909
1910
1911
1912
1913
1914
1915
1916
1917
1918
1919
1920
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930
1931
1932
1933
1934
1935
1936
1937
1938
1939
1940
1941
1942
1943
1944
1945
1946
1947
1948
1949
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
2026
2027
2028
2029
2030
2031
2032
2033
2034
2035
2036
2037
2038
2039
2040
2041
2042
2043
2044
2045
2046
2047
2048
2049
2050
2051
2052
2053
2054
2055
2056
2057
2058
2059
2060
2061
2062
2063
2064
2065
2066
2067
2068
2069
2070
2071
2072
2073
2074
2075
2076
2077
2078
2079
2080
2081
2082
2083
2084
2085
2086
2087
2088
2089
2090
2091
2092
2093
2094
2095
2096
2097
2098
2099
2100
2101
2102
2103
2104
2105
2106
2107
2108
2109
2110
2111
2112
2113
2114
2115
2116
2117
2118
2119
2120
2121
2122
2123
2124
2125
2126
2127
2128
2129
2130
2131
2132
2133
2134
2135
2136
2137
2138
2139
2140
2141
2142
2143
2144
2145
2146
2147
2148
2149
2150
2151
2152
2153
2154
2155
2156
2157
2158
2159
2160
2161
2162
2163
2164
2165
2166
2167
2168
2169
2170
2171
2172
2173
2174
2175
2176
2177
2178
2179
2180
2181
2182
2183
2184
2185
2186
2187
2188
2189
2190
2191
2192
2193
2194
2195
2196
2197
2198
2199
2200
2201
2202
2203
2204
2205
2206
2207
2208
2209
2210
2211
2212
2213
2214
2215
2216
2217
2218
2219
2220
2221
2222
2223
2224
2225
2226
2227
2228
2229
2230
2231
2232
2233
2234
2235
2236
2237
2238
2239
2240
2241
2242
2243
2244
2245
2246
2247
2248
2249
2250
2251
2252
2253
2254
2255
2256
2257
2258
2259
2260
2261
2262
2263
2264
2265
2266
2267
2268
2269
2270
2271
2272
2273
2274
2275
2276
2277
2278
2279
2280
2281
2282
2283
2284
2285
2286
2287
2288
2289
2290
2291
2292
2293
2294
2295
2296
2297
2298
2299
2300
2301
2302
2303
2304
2305
2306
2307
2308
2309
2310
2311
2312
2313
2314
2315
2316
2317
2318
2319
2320
2321
2322
2323
2324
2325
2326
2327
2328
2329
2330
2331
2332
2333
2334
2335
2336
2337
2338
2339
2340
2341
2342
2343
2344
2345
2346
2347
2348
2349
2350
2351
2352
2353
2354
2355
2356
2357
2358
2359
2360
2361
2362
2363
2364
2365
2366
2367
2368
2369
2370
2371
2372
2373
2374
2375
2376
2377
2378
2379
2380
2381
2382
2383
2384
2385
2386
2387
2388
2389
2390
2391
2392
2393
2394
2395
2396
2397
2398
2399
2400
2401
2402
2403
2404
2405
2406
2407
2408
2409
2410
2411
2412
2413
2414
2415
2416
2417
2418
2419
2420
2421
2422
2423
2424
2425
2426
2427
2428
2429
2430
2431
2432
2433
2434
2435
2436
2437
2438
2439
2440
2441
2442
2443
2444
2445
2446
2447
2448
2449
2450
2451
2452
2453
2454
2455
2456
2457
2458
2459
2460
2461
2462
2463
2464
2465
2466
2467
2468
2469
2470
2471
2472
2473
2474
2475
2476
2477
2478
2479
2480
2481
2482
2483
2484
2485
2486
2487
2488
2489
2490
2491
2492
2493
2494
2495
2496
2497
2498
2499
2500
2501
2502
2503
2504
2505
2506
2507
2508
2509
2510
2511
2512
2513
2514
2515
2516
2517
2518
2519
2520
2521
2522
2523
2524
2525
2526
2527
2528
2529
2530
2531
2532
2533
2534
2535
2536
2537
2538
2539
2540
2541
2542
2543
2544
2545
2546
2547
2548
2549
2550
2551
2552
2553
2554
2555
2556
2557
2558
2559
2560
2561
2562
2563
2564
2565
2566
2567
2568
2569
2570
2571
2572
2573
2574
2575
2576
2577
2578
2579
2580
2581
2582
2583
2584
2585
2586
2587
2588
2589
2590
2591
2592
2593
2594
2595
2596
2597
2598
2599
2600
2601
2602
2603
2604
2605
2606
2607
2608
2609
2610
2611
2612
2613
2614
2615
2616
2617
2618
2619
2620
2621
2622
2623
2624
2625
2626
2627
2628
2629
2630
2631
2632
2633
2634
2635
2636
2637
2638
2639
2640
2641
2642
2643
2644
2645
2646
2647
2648
2649
2650
2651
2652
2653
2654
2655
2656
2657
2658
2659
2660
2661
2662
2663
2664
2665
2666
2667
2668
2669
2670
2671
2672
2673
2674
2675
2676
2677
2678
2679
2680
2681
2682
2683
2684
2685
2686
2687
2688
2689
2690
2691
2692
2693
2694
2695
2696
2697
2698
2699
2700
2701
2702
2703
2704
2705
2706
2707
2708
2709
2710
2711
2712
If you read this file _as_is_, just ignore the funny characters you see.
It is written in the POD format (see pod/perlpod.pod) which is specially
designed to be readable as is.

=head1 NAME

INSTALL - Build and Installation guide for perl 5.

=head1 SYNOPSIS

First, make sure you have an up-to-date version of Perl.  If you
didn't get your Perl source from CPAN, check the latest version at
http://www.cpan.org/src/.  Perl uses a version scheme where even-numbered
subreleases (like 5.8.x and 5.10.x) are stable maintenance releases and
odd-numbered subreleases (like 5.7.x and 5.9.x) are unstable
development releases.  Development releases should not be used in
production environments.  Fixes and new features are first carefully
tested in development releases and only if they prove themselves to be
worthy will they be migrated to the maintenance releases.

The basic steps to build and install perl 5 on a Unix system with all
the defaults are to run, from a freshly unpacked source tree:

	sh Configure -de
	make
	make test
	make install

Each of these is explained in further detail below.

The above commands will install Perl to /usr/local (or some other
platform-specific directory -- see the appropriate file in hints/.)
If that's not okay with you, you can run Configure interactively, by
just typing "sh Configure" (without the -de args). You can also specify
any prefix location by adding "-Dprefix='/some/dir'" to Configure's args.
To explicitly name the perl binary, use the command
"make install PERLNAME=myperl".

Building perl from source requires an ANSI compliant C compiler.
A minimum of C89 is required. Some features available in C99 will
be probed for and used when found. The perl build process does not
rely on anything more than C89.

These options, and many more, are explained in further detail below.

If you're building perl from a git repository, you should also consult
the documentation in pod/perlgit.pod for information on that special
circumstance.

If you have problems, corrections, or questions, please see
L<"Reporting Problems"> below.

For information on what's new in this release, see the
pod/perldelta.pod file.  For more information about how to find more
specific detail about changes, see the Changes file.

=head1 DESCRIPTION

This document is written in pod format as an easy way to indicate its
structure.  The pod format is described in pod/perlpod.pod, but you can
read it as is with any pager or editor.  Headings and items are marked
by lines beginning with '='.  The other mark-up used is

    B<text>     embolden text, used for switches, programs or commands
    C<code>	literal code
    L<name>     A link (cross reference) to name
    F<file>     A filename

Although most of the defaults are probably fine for most users,
you should probably at least skim through this document before
proceeding.

In addition to this file, check if there is a README file specific to
your operating system, since it may provide additional or different
instructions for building Perl.  If there is a hint file for your
system (in the hints/ directory) you might also want to read it
for even more information.

For additional information about porting Perl, see the section on
L<"Porting information"> below, and look at the files in the Porting/
directory.

=head1 PRELIMINARIES

=head2 Changes and Incompatibilities

Please see pod/perldelta.pod for a description of the changes and
potential incompatibilities introduced with this release.  A few of
the most important issues are listed below, but you should refer
to pod/perldelta.pod for more detailed information.

B<WARNING:> This version is not binary compatible with earlier versions
of Perl.  If you have built extensions (i.e. modules that include C code)
using an earlier version of Perl, you will need to rebuild and reinstall
those extensions.

Pure perl modules without XS or C code should continue to work fine
without reinstallation.  See the discussion below on
L<"Coexistence with earlier versions of perl 5"> for more details.

The standard extensions supplied with Perl will be handled automatically.

On a related issue, old modules may possibly be affected by the changes
in the Perl language in the current release.  Please see
pod/perldelta.pod for a description of what's changed.  See your
installed copy of the perllocal.pod file for a (possibly incomplete)
list of locally installed modules.  Also see the L<CPAN> module's
C<autobundle> function for one way to make a "bundle" of your currently
installed modules.

=head1 Run Configure

Configure will figure out various things about your system.  Some
things Configure will figure out for itself, other things it will ask
you about.  To accept the default, just press RETURN.   The default is
almost always okay.  It is normal for some things to be "NOT found",
since Configure often searches for many different ways of performing
the same function.

At any Configure prompt, you can type  &-d  and Configure will use the
defaults from then on.

After it runs, Configure will perform variable substitution on all the
*.SH files and offer to run make depend.

The results of a Configure run are stored in the config.sh and Policy.sh
files.

=head2 Common Configure options

Configure supports a number of useful options.  Run

	Configure -h

to get a listing.  See the Porting/Glossary file for a complete list of
Configure variables you can set and their definitions.

=over 4

=item C compiler

To compile with gcc, if it's not the default compiler on your
system, you should run

	sh Configure -Dcc=gcc

This is the preferred way to specify gcc (or any another alternative
compiler) so that the hints files can set appropriate defaults.

=item Installation prefix

By default, for most systems, perl will be installed in
/usr/local/{bin, lib, man}.  (See L<"Installation Directories">
and L<"Coexistence with earlier versions of perl 5"> below for
further details.)

You can specify a different 'prefix' for the default installation
directory when Configure prompts you, or by using the Configure command
line option -Dprefix='/some/directory', e.g.

	sh Configure -Dprefix=/opt/perl

If your prefix contains the string "perl", then the suggested
directory structure is simplified.  For example, if you use
prefix=/opt/perl, then Configure will suggest /opt/perl/lib instead of
/opt/perl/lib/perl5/.  Again, see L<"Installation Directories"> below
for more details.  Do not include a trailing slash, (i.e. /opt/perl/)
or you may experience odd test failures.

NOTE:  You must not specify an installation directory that is the same
as or below your perl source directory.  If you do, installperl will
attempt infinite recursion.

=item /usr/bin/perl

It may seem obvious, but Perl is useful only when users can easily
find it.  It's often a good idea to have both /usr/bin/perl and
/usr/local/bin/perl be symlinks to the actual binary.  Be especially
careful, however, not to overwrite a version of perl supplied by your
vendor unless you are sure you know what you are doing.  If you insist
on replacing your vendor's perl, useful information on how it was
configured may be found with

	perl -V:config_args

(Check the output carefully, however, since this doesn't preserve
spaces in arguments to Configure.  For that, you have to look carefully
at config_arg1, config_arg2, etc.)

By default, Configure will not try to link /usr/bin/perl to the current
version of perl.  You can turn on that behavior by running

	Configure -Dinstallusrbinperl

or by answering 'yes' to the appropriate Configure prompt.

In any case, system administrators are strongly encouraged to put
(symlinks to) perl and its accompanying utilities, such as perldoc,
into a directory typically found along a user's PATH, or in another
obvious and convenient place.

=item Building a development release

For development releases (odd subreleases, like 5.9.x) if you want to
use Configure -d, you will also need to supply -Dusedevel to Configure,
because the default answer to the question "do you really want to
Configure a development version?" is "no".  The -Dusedevel skips that
sanity check.

=back

If you are willing to accept all the defaults, and you want terse
output, you can run

	sh Configure -des

=head2 Altering Configure variables for C compiler switches etc.

For most users, most of the Configure defaults are fine, or can easily
be set on the Configure command line.  However, if Configure doesn't
have an option to do what you want, you can change Configure variables
after the platform hints have been run by using Configure's -A switch.
For example, here's how to add a couple of extra flags to C compiler
invocations:

	sh Configure -Accflags="-DPERL_EXTERNAL_GLOB -DNO_HASH_SEED"

To clarify, those ccflags values are not Configure options; if passed to
Configure directly, they won't do anything useful (they will define a
variable in config.sh, but without taking any action based upon it).
But when passed to the compiler, those flags will activate #ifdefd code.

For more help on Configure switches, run

	sh Configure -h

=head2 Major Configure-time Build Options

There are several different ways to Configure and build perl for your
system.  For most users, the defaults are sensible and will work.
Some users, however, may wish to further customize perl.  Here are
some of the main things you can change.

=head3 Threads

On some platforms, perl can be compiled with support for threads.  To
enable this, run

	sh Configure -Dusethreads

The default is to compile without thread support.

Perl used to have two different internal threads implementations.  The
current model (available internally since 5.6, and as a user-level module
since 5.8) is called interpreter-based implementation (ithreads), with
one interpreter per thread, and explicit sharing of data. The (deprecated)
5.005 version (5005threads) was removed for release 5.10.

The 'threads' module is for use with the ithreads implementation.  The
'Thread' module emulates the old 5005threads interface on top of the
current ithreads model.

When using threads, perl uses a dynamically-sized buffer for some of
the thread-safe library calls, such as those in the getpw*() family.
This buffer starts small, but it will keep growing until the result
fits.  To get a fixed upper limit, you should compile Perl with
PERL_REENTRANT_MAXSIZE defined to be the number of bytes you want.  One
way to do this is to run Configure with
C<-Accflags=-DPERL_REENTRANT_MAXSIZE=65536>.

=head3 Large file support

Since Perl 5.6.0, Perl has supported large files (files larger than
2 gigabytes), and in many common platforms like Linux or Solaris this
support is on by default.

This is both good and bad. It is good in that you can use large files,
seek(), stat(), and -s them.  It is bad in that if you are interfacing
Perl using some extension, the components you are connecting to must also
be large file aware: if Perl thinks files can be large but the other
parts of the software puzzle do not understand the concept, bad things
will happen.

There's also one known limitation with the current large files
implementation: unless you also have 64-bit integers (see the next
section), you cannot use the printf/sprintf non-decimal integer formats
like C<%x> to print filesizes.  You can use C<%d>, though.

If you want to compile perl without large file support, use

    sh Configure -Uuselargefiles

=head3 64 bit support

If your platform does not run natively at 64 bits, but can simulate
them with compiler flags and/or C<long long> or C<int64_t>,
you can build a perl that uses 64 bits.

There are actually two modes of 64-bitness: the first one is achieved
using Configure -Duse64bitint and the second one using Configure
-Duse64bitall.  The difference is that the first one is minimal and
the second one maximal.  The first works in more places than the second.

The C<use64bitint> option does only as much as is required to get
64-bit integers into Perl (this may mean, for example, using "long
longs") while your memory may still be limited to 2 gigabytes (because
your pointers could still be 32-bit).  Note that the name C<64bitint>
does not imply that your C compiler will be using 64-bit C<int>s (it
might, but it doesn't have to).  The C<use64bitint> simply means that
you will be able to have 64 bit-wide scalar values.

The C<use64bitall> option goes all the way by attempting to switch
integers (if it can), longs (and pointers) to being 64-bit.  This may
create an even more binary incompatible Perl than -Duse64bitint: the
resulting executable may not run at all in a 32-bit box, or you may
have to reboot/reconfigure/rebuild your operating system to be 64-bit
aware.

Natively 64-bit systems need neither -Duse64bitint nor -Duse64bitall.
On these systems, it might be the default compilation mode, and there
is currently no guarantee that passing no use64bitall option to the
Configure process will build a 32bit perl. Implementing -Duse32bit*
options is planned for a future release of perl.

=head3 Long doubles

In some systems you may be able to use long doubles to enhance the
range and precision of your double precision floating point numbers
(that is, Perl's numbers).  Use Configure -Duselongdouble to enable
this support (if it is available).

Note that the exact format and range of long doubles varies:
the most common is the x86 80-bit (64 bits of mantissa) format,
but there are others, with different mantissa and exponent ranges.

=head3 "more bits"

You can "Configure -Dusemorebits" to turn on both the 64-bit support
and the long double support.

=head3 quadmath

One option for more precision is that gcc 4.6 and later have a library
called quadmath, which implements the IEEE 754 quadruple precision
(128-bit, 113 bits of mantissa) floating point numbers.  The library
works at least on x86 and ia64 platforms.  It may be part of your gcc
installation, or you may need to install it separately.

With "Configure -Dusequadmath" you can try enabling its use, but note
the compiler dependency, you may need to also add "-Dcc=...".
At C level the type is called C<__float128> (note, not "long double"),
but Perl source knows it as NV.  (This is not "long doubles".)

=head3 Algorithmic Complexity Attacks on Hashes

Perl 5.18 reworked the measures used to secure its hash function
from algorithmic complexity attacks.  By default it will build with
all of these measures enabled along with support for controlling and
disabling them via environment variables.

You can override various aspects of this feature by defining various
symbols during configure. An example might be:

    Configure -Accflags=-DPERL_HASH_FUNC_SIPHASH

B<Unless stated otherwise these options are considered experimental or
insecure and are not recommended for production use.>

Perl 5.18 includes support for multiple hash functions, and changed
the default (to ONE_AT_A_TIME_HARD), you can choose a different
algorithm by defining one of the following symbols. Note that as of
Perl 5.18 we can only recommend use of the default or SIPHASH. All
the others are known to have security issues and are for research
purposes only.

    PERL_HASH_FUNC_SIPHASH
    PERL_HASH_FUNC_SDBM
    PERL_HASH_FUNC_DJB2
    PERL_HASH_FUNC_SUPERFAST
    PERL_HASH_FUNC_MURMUR3
    PERL_HASH_FUNC_ONE_AT_A_TIME
    PERL_HASH_FUNC_ONE_AT_A_TIME_HARD
    PERL_HASH_FUNC_ONE_AT_A_TIME_OLD

Perl 5.18 randomizes the order returned by keys(), values(), and each(),
and allows controlling this behavior by using of the PERL_PERTURB_KEYS
option. You can disable this option entirely with the define:

    PERL_PERTURB_KEYS_DISABLED

You can disable the environment variable checks and specify the type of
key traversal randomization to be used by defining one of these:

    PERL_PERTURB_KEYS_RANDOM
    PERL_PERTURB_KEYS_DETERMINISTIC

In Perl 5.18 the seed used for the hash function is randomly selected
at process start which can be overridden by specifying a seed by setting
the PERL_HASH_SEED environment variable.

You can change this behavior by building perl with the

   USE_HASH_SEED_EXPLICIT

define, in which case one has to explicitly set the PERL_HASH_SEED
environment variable to enable the security feature or by adding

    NO_HASH_SEED

to the compilation flags to completely disable the randomisation feature.
Note these modes are poorly tested, insecure and not recommended.

B<Perl has never guaranteed any ordering of the hash keys>, and the
ordering has already changed several times during the lifetime of Perl
5.  Also, the ordering of hash keys has always been, and continues to
be, affected by the insertion order.  Note that because of this
randomisation for example the Data::Dumper results will be different
between different runs of Perl, since Data::Dumper by default dumps
hashes "unordered".  The use of the Data::Dumper C<Sortkeys> option is
recommended.

See L<perlrun/PERL_HASH_SEED> and L<perlrun/PERL_PERTURB_KEYS> for
details on the environment variables, and L<perlsec/Algorithmic
Complexity Attacks> for further security details.

=head3 SOCKS

Perl can be configured to be 'socksified', that is, to use the SOCKS
TCP/IP proxy protocol library.  SOCKS is used to give applications
access to transport layer network proxies.  Perl supports only SOCKS
Version 5.  The corresponding Configure option is -Dusesocks.
You can find more about SOCKS from wikipedia at
L<http://en.wikipedia.org/wiki/SOCKS>.

=head3 Dynamic Loading

By default, Configure will compile perl to use dynamic loading.
If you want to force perl to be compiled completely
statically, you can either choose this when Configure prompts you or
you can use the Configure command line option -Uusedl.
With this option, you won't be able to use any new extension
(XS) module without recompiling perl itself.

=head3 Building a shared Perl library

Currently, for most systems, the main perl executable is built by
linking the "perl library" libperl.a with perlmain.o, your static
extensions, and various extra libraries, such as -lm.

On systems that support dynamic loading, it may be possible to
replace libperl.a with a shared libperl.so.  If you anticipate building
several different perl binaries (e.g. by embedding libperl into
different programs, or by using the optional compiler extension), then
you might wish to build a shared libperl.so so that all your binaries
can share the same library.

The disadvantages are that there may be a significant performance
penalty associated with the shared libperl.so, and that the overall
mechanism is still rather fragile with respect to different versions
and upgrades.

In terms of performance, on my test system (Solaris 2.5_x86) the perl
test suite took roughly 15% longer to run with the shared libperl.so.
Your system and typical applications may well give quite different
results.

The default name for the shared library is typically something like
libperl.so.5.8.8 (for Perl 5.8.8), or libperl.so.588, or simply
libperl.so.  Configure tries to guess a sensible naming convention
based on your C library name.  Since the library gets installed in a
version-specific architecture-dependent directory, the exact name
isn't very important anyway, as long as your linker is happy.

You can elect to build a shared libperl by

	sh Configure -Duseshrplib

To build a shared libperl, the environment variable controlling shared
library search (LD_LIBRARY_PATH in most systems, DYLD_LIBRARY_PATH for
Darwin, LD_LIBRARY_PATH/SHLIB_PATH
for HP-UX, LIBPATH for AIX, PATH for Cygwin) must be set up to include
the Perl build directory because that's where the shared libperl will
be created.  Configure arranges makefile to have the correct shared
library search settings.  You can find the name of the environment
variable Perl thinks works in your your system by

	grep ldlibpthname config.sh

However, there are some special cases where manually setting the
shared library path might be required.  For example, if you want to run
something like the following with the newly-built but not-yet-installed
./perl:

        ./perl -MTestInit t/misc/failing_test.t

or

        ./perl -Ilib ~/my_mission_critical_test

then you need to set up the shared library path explicitly.
You can do this with

   LD_LIBRARY_PATH=`pwd`:$LD_LIBRARY_PATH; export LD_LIBRARY_PATH

for Bourne-style shells, or

   setenv LD_LIBRARY_PATH `pwd`

for Csh-style shells.  (This procedure may also be needed if for some
unexpected reason Configure fails to set up makefile correctly.) (And
again, it may be something other than LD_LIBRARY_PATH for you, see above.)

You can often recognize failures to build/use a shared libperl from error
messages complaining about a missing libperl.so (or libperl.sl in HP-UX),
for example:

    18126:./miniperl: /sbin/loader: Fatal Error: cannot map libperl.so

There is also an potential problem with the shared perl library if you
want to have more than one "flavor" of the same version of perl (e.g.
with and without -DDEBUGGING).  For example, suppose you build and
install a standard Perl 5.10.0 with a shared library.  Then, suppose you
try to build Perl 5.10.0 with -DDEBUGGING enabled, but everything else
the same, including all the installation directories.  How can you
ensure that your newly built perl will link with your newly built
libperl.so.8 rather with the installed libperl.so.8?  The answer is
that you might not be able to.  The installation directory is encoded
in the perl binary with the LD_RUN_PATH environment variable (or
equivalent ld command-line option).  On Solaris, you can override that
with LD_LIBRARY_PATH; on Linux, you can only override at runtime via
LD_PRELOAD, specifying the exact filename you wish to be used; and on
Digital Unix, you can override LD_LIBRARY_PATH by setting the
_RLD_ROOT environment variable to point to the perl build directory.

In other words, it is generally not a good idea to try to build a perl
with a shared library if $archlib/CORE/$libperl already exists from a
previous build.

A good workaround is to specify a different directory for the
architecture-dependent library for your -DDEBUGGING version of perl.
You can do this by changing all the *archlib* variables in config.sh to
point to your new architecture-dependent library.

=head3 Environment access

Perl often needs to write to the program's environment, such as when
C<%ENV> is assigned to. Many implementations of the C library function
C<putenv()> leak memory, so where possible perl will manipulate the
environment directly to avoid these leaks. The default is now to perform
direct manipulation whenever perl is running as a stand alone interpreter,
and to call the safe but potentially leaky C<putenv()> function when the
perl interpreter is embedded in another application. You can force perl
to always use C<putenv()> by compiling with
C<-Accflags="-DPERL_USE_SAFE_PUTENV">, see section L</"Altering Configure
variables for C compiler switches etc.">.  You can force an embedded perl
to use direct manipulation by setting C<PL_use_safe_putenv = 0;> after
the C<perl_construct()> call.

=head2 Installation Directories

The installation directories can all be changed by answering the
appropriate questions in Configure.  For convenience, all the installation
questions are near the beginning of Configure.  Do not include trailing
slashes on directory names.  At any point during the Configure process,
you can answer a question with  &-d  and Configure will use the defaults
from then on.  Alternatively, you can

	grep '^install' config.sh

after Configure has run to verify the installation paths.

The defaults are intended to be reasonable and sensible for most
people building from sources.  Those who build and distribute binary
distributions or who export perl to a range of systems will probably
need to alter them.  If you are content to just accept the defaults,
you can safely skip the next section.

The directories set up by Configure fall into three broad categories.

=over 4

=item Directories for the perl distribution

By default, Configure will use the following directories for 5.24.1.
$version is the full perl version number, including subversion, e.g.
5.12.3, and $archname is a string like sun4-sunos,
determined by Configure.  The full definitions of all Configure
variables are in the file Porting/Glossary.

    Configure variable	Default value
    $prefixexp		/usr/local
    $binexp		$prefixexp/bin
    $scriptdirexp	$prefixexp/bin
    $privlibexp		$prefixexp/lib/perl5/$version
    $archlibexp		$prefixexp/lib/perl5/$version/$archname
    $man1direxp		$prefixexp/man/man1
    $man3direxp		$prefixexp/man/man3
    $html1direxp	(none)
    $html3direxp	(none)

$prefixexp is generated from $prefix, with ~ expansion done to convert
home directories into absolute paths. Similarly for the other variables
listed. As file system calls do not do this, you should always reference
the ...exp variables, to support users who build perl in their home
directory.

Actually, Configure recognizes the SVR3-style
/usr/local/man/l_man/man1 directories, if present, and uses those
instead.  Also, if $prefix contains the string "perl", the library
directories are simplified as described below.  For simplicity, only
the common style is shown here.

=item Directories for site-specific add-on files

After perl is installed, you may later wish to add modules (e.g. from
CPAN) or scripts.  Configure will set up the following directories to
be used for installing those add-on modules and scripts.

   Configure        Default
   variable          value
 $siteprefixexp    $prefixexp
 $sitebinexp       $siteprefixexp/bin
 $sitescriptexp    $siteprefixexp/bin
 $sitelibexp       $siteprefixexp/lib/perl5/site_perl/$version
 $sitearchexp
               $siteprefixexp/lib/perl5/site_perl/$version/$archname
 $siteman1direxp   $siteprefixexp/man/man1
 $siteman3direxp   $siteprefixexp/man/man3
 $sitehtml1direxp  (none)
 $sitehtml3direxp  (none)

By default, ExtUtils::MakeMaker will install architecture-independent
modules into $sitelib and architecture-dependent modules into $sitearch.

=item Directories for vendor-supplied add-on files

Lastly, if you are building a binary distribution of perl for
distribution, Configure can optionally set up the following directories
for you to use to distribute add-on modules.

   Configure          Default
   variable            value
 $vendorprefixexp    (none)

 (The next ones are set only if vendorprefix is set.)

 $vendorbinexp       $vendorprefixexp/bin
 $vendorscriptexp    $vendorprefixexp/bin
 $vendorlibexp       $vendorprefixexp/lib/perl5/vendor_perl/$version
 $vendorarchexp
           $vendorprefixexp/lib/perl5/vendor_perl/$version/$archname
 $vendorman1direxp   $vendorprefixexp/man/man1
 $vendorman3direxp   $vendorprefixexp/man/man3
 $vendorhtml1direxp  (none)
 $vendorhtml3direxp  (none)

These are normally empty, but may be set as needed.  For example,
a vendor might choose the following settings:

 $prefix           /usr
 $siteprefix       /usr/local
 $vendorprefix     /usr

This would have the effect of setting the following:

 $binexp           /usr/bin
 $scriptdirexp     /usr/bin
 $privlibexp       /usr/lib/perl5/$version
 $archlibexp       /usr/lib/perl5/$version/$archname
 $man1direxp       /usr/man/man1
 $man3direxp       /usr/man/man3

 $sitebinexp       /usr/local/bin
 $sitescriptexp    /usr/local/bin
 $sitelibexp       /usr/local/lib/perl5/site_perl/$version
 $sitearchexp      /usr/local/lib/perl5/site_perl/$version/$archname
 $siteman1direxp   /usr/local/man/man1
 $siteman3direxp   /usr/local/man/man3

 $vendorbinexp     /usr/bin
 $vendorscriptexp  /usr/bin
 $vendorlibexp     /usr/lib/perl5/vendor_perl/$version
 $vendorarchexp    /usr/lib/perl5/vendor_perl/$version/$archname
 $vendorman1direxp /usr/man/man1
 $vendorman3direxp /usr/man/man3

Note how in this example, the vendor-supplied directories are in the
/usr hierarchy, while the directories reserved for the end user are in
the /usr/local hierarchy.

The entire installed library hierarchy is installed in locations with
version numbers, keeping the installations of different versions distinct.
However, later installations of Perl can still be configured to search
the installed libraries corresponding to compatible earlier versions.
See L<"Coexistence with earlier versions of perl 5"> below for more
details on how Perl can be made to search older version directories.

Of course you may use these directories however you see fit.  For
example, you may wish to use $siteprefix for site-specific files that
are stored locally on your own disk and use $vendorprefix for
site-specific files that are stored elsewhere on your organization's
network.  One way to do that would be something like

 sh Configure -Dsiteprefix=/usr/local -Dvendorprefix=/usr/share/perl

=item otherlibdirs

As a final catch-all, Configure also offers an $otherlibdirs
variable.  This variable contains a colon-separated list of additional
directories to add to @INC.  By default, it will be empty.
Perl will search these directories (including architecture and
version-specific subdirectories) for add-on modules and extensions.

For example, if you have a bundle of perl libraries from a previous
installation, perhaps in a strange place:

	Configure -Dotherlibdirs=/usr/lib/perl5/site_perl/5.8.1

=item APPLLIB_EXP

There is one other way of adding paths to @INC at perl build time, and
that is by setting the APPLLIB_EXP C pre-processor token to a colon-
separated list of directories, like this

       sh Configure -Accflags='-DAPPLLIB_EXP=\"/usr/libperl\"'

The directories defined by APPLLIB_EXP get added to @INC I<first>,
ahead of any others, and so provide a way to override the standard perl
modules should you, for example, want to distribute fixes without
touching the perl distribution proper.  And, like otherlib dirs,
version and architecture specific subdirectories are also searched, if
present, at run time.  Of course, you can still search other @INC
directories ahead of those in APPLLIB_EXP by using any of the standard
run-time methods: $PERLLIB, $PERL5LIB, -I, use lib, etc.

=item usesitecustomize

Run-time customization of @INC can be enabled with:

	sh Configure -Dusesitecustomize

which will define USE_SITECUSTOMIZE and $Config{usesitecustomize}.
When enabled, this makes perl run F<$sitelibexp/sitecustomize.pl> before
anything else.  This script can then be set up to add additional
entries to @INC.

=item Man Pages

By default, man pages will be installed in $man1dir and $man3dir, which
are normally /usr/local/man/man1 and /usr/local/man/man3.  If you
want to use a .3pm suffix for perl man pages, you can do that with

	sh Configure -Dman3ext=3pm

=item HTML pages

Currently, the standard perl installation does not do anything with
HTML documentation, but that may change in the future.  Further, some
add-on modules may wish to install HTML documents.  The html Configure
variables listed above are provided if you wish to specify where such
documents should be placed.  The default is "none", but will likely
eventually change to something useful based on user feedback.

=back

Some users prefer to append a "/share" to $privlib and $sitelib
to emphasize that those directories can be shared among different
architectures.

Note that these are just the defaults.  You can actually structure the
directories any way you like.  They don't even have to be on the same
filesystem.

Further details about the installation directories, maintenance and
development subversions, and about supporting multiple versions are
discussed in L<"Coexistence with earlier versions of perl 5"> below.

If you specify a prefix that contains the string "perl", then the
library directory structure is slightly simplified.  Instead of
suggesting $prefix/lib/perl5/, Configure will suggest $prefix/lib.

Thus, for example, if you Configure with
-Dprefix=/opt/perl, then the default library directories for 5.9.0 are

    Configure variable	Default value
	$privlib	/opt/perl/lib/5.9.0
	$archlib	/opt/perl/lib/5.9.0/$archname
	$sitelib	/opt/perl/lib/site_perl/5.9.0
	$sitearch	/opt/perl/lib/site_perl/5.9.0/$archname

=head2 Changing the installation directory

Configure distinguishes between the directory in which perl (and its
associated files) should be installed, and the directory in which it
will eventually reside.  For most sites, these two are the same; for
sites that use AFS, this distinction is handled automatically.
However, sites that use package management software such as rpm or
dpkg, or users building binary packages for distribution may also
wish to install perl into a different directory before moving perl
to its final destination.  There are two ways to do that:

=over 4

=item installprefix

To install perl under the /tmp/perl5 directory, use the following
command line:

    sh Configure -Dinstallprefix=/tmp/perl5

(replace /tmp/perl5 by a directory of your choice).

Beware, though, that if you go to try to install new add-on
modules, they too will get installed in under '/tmp/perl5' if you
follow this example.  That's why it's usually better to use DESTDIR,
as shown in the next section.

=item DESTDIR

If you need to install perl on many identical systems, it is convenient
to compile it once and create an archive that can be installed on
multiple systems.  Suppose, for example, that you want to create an
archive that can be installed in /opt/perl.  One way to do that is by
using the DESTDIR variable during C<make install>.  The DESTDIR is
automatically prepended to all the installation paths.  Thus you
simply do:

    sh Configure -Dprefix=/opt/perl -des
    make
    make test
    make install DESTDIR=/tmp/perl5
    cd /tmp/perl5/opt/perl
    tar cvf /tmp/perl5-archive.tar .

=back

=head2 Relocatable @INC

To create a relocatable perl tree, use the following command line:

    sh Configure -Duserelocatableinc

Then the paths in @INC (and everything else in %Config) can be
optionally located via the path of the perl executable.

That means that, if the string ".../" is found at the start of any
path, it's substituted with the directory of $^X. So, the relocation
can be configured on a per-directory basis, although the default with
"-Duserelocatableinc" is that everything is relocated. The initial
install is done to the original configured prefix.

This option is not compatible with the building of a shared libperl
("-Duseshrplib"), because in that case perl is linked with an hard-coded
rpath that points at the libperl.so, that cannot be relocated.

=head2 Site-wide Policy settings

After Configure runs, it stores a number of common site-wide "policy"
answers (such as installation directories) in the Policy.sh file.
If you want to build perl on another system using the same policy
defaults, simply copy the Policy.sh file to the new system's perl build
directory, and Configure will use it. This will work even if Policy.sh was
generated for another version of Perl, or on a system with a
different architecture and/or operating system. However, in such cases,
you should review the contents of the file before using it: for
example, your new target may not keep its man pages in the same place
as the system on which the file was generated.

Alternatively, if you wish to change some or all of those policy
answers, you should

	rm -f Policy.sh

to ensure that Configure doesn't re-use them.

Further information is in the Policy_sh.SH file itself.

If the generated Policy.sh file is unsuitable, you may freely edit it
to contain any valid shell commands.  It will be run just after the
platform-specific hints files.

=head2 Disabling older versions of Perl

Configure will search for binary compatible versions of previously
installed perl binaries in the tree that is specified as target tree,
and these will be used as locations to search for modules by the perl
being built. The list of perl versions found will be put in the Configure
variable inc_version_list.

To disable this use of older perl modules, even completely valid pure
perl modules, you can specify to not include the paths found:

       sh Configure -Dinc_version_list=none ...

If you do want to use modules from some previous perl versions, the
variable must contain a space separated list of directories under the
site_perl directory, and has to include architecture-dependent
directories separately, eg.

       sh Configure -Dinc_version_list="5.16.0/x86_64-linux 5.16.0" ...

When using the newer perl, you can add these paths again in the
PERL5LIB environment variable or with perl's -I runtime option.

=head2 Building Perl outside of the source directory

Sometimes it is desirable to build Perl in a directory different from
where the sources are, for example if you want to keep your sources
read-only, or if you want to share the sources between different binary
architectures.  You can do this (if your file system supports symbolic
links) by

	mkdir /tmp/perl/build/directory
	cd /tmp/perl/build/directory
	sh /path/to/perl/source/Configure -Dmksymlinks ...

This will create in /tmp/perl/build/directory a tree of symbolic links
pointing to files in /path/to/perl/source.  The original files are left
unaffected.  After Configure has finished you can just say

	make
	make test
	make install

as usual, and Perl will be built in /tmp/perl/build/directory.

=head2 Building a debugging perl

You can run perl scripts under the perl debugger at any time with
B<perl -d your_script>.  If, however, you want to debug perl itself,
you probably want to have support for perl internal debugging code
(activated by adding -DDEBUGGING to ccflags), and/or support for the
system debugger by adding -g to the optimisation flags. For that,
use the parameter:

	sh Configure -DDEBUGGING

or

	sh Configure -DDEBUGGING=<mode>

For a more eye appealing call, -DEBUGGING is defined to be an alias
for -DDEBUGGING. For both, the -U calls are also supported, in order
to be able to overrule the hints or Policy.sh settings.

Here are the DEBUGGING modes:

=over 4

=item -DDEBUGGING

=item -DEBUGGING

=item -DEBUGGING=both

Sets both -DDEBUGGING in the ccflags, and adds -g to optimize.

You can actually specify -g and -DDEBUGGING independently (see below),
but usually it's convenient to have both.

=item -DEBUGGING=-g

=item -Doptimize=-g

Adds -g to optimize, but does not set -DDEBUGGING.

(Note:  Your system may actually require something like cc -g2.
Check your man pages for cc(1) and also any hint file for your system.)

=item -DEBUGGING=none

=item -UDEBUGGING

Removes -g from optimize, and -DDEBUGGING from ccflags.

=back

If you are using a shared libperl, see the warnings about multiple
versions of perl under L<Building a shared Perl library>.

Note that a perl built with -DDEBUGGING will be much bigger and will run
much, much more slowly than a standard perl.

=head2 DTrace support

On platforms where DTrace is available, it may be enabled by
using the -Dusedtrace option to Configure. DTrace probes are available
for subroutine entry (sub-entry) and subroutine exit (sub-exit). Here's a
simple D script that uses them:

  perl$target:::sub-entry, perl$target:::sub-return {
    printf("%s %s (%s:%d)\n", probename == "sub-entry" ? "->" : "<-",
              copyinstr(arg0), copyinstr(arg1), arg2);
  }


=head2 Extensions

Perl ships with a number of standard extensions.  These are contained
in the ext/ subdirectory.

By default, Configure will offer to build every extension which appears
to be supported.  For example, Configure will offer to build GDBM_File
only if it is able to find the gdbm library.

To disable certain extensions so that they are not built, use the
-Dnoextensions=... and -Donlyextensions=... options.  They both accept
a space-separated list of extensions, such as C<IPC/SysV>. The extensions
listed in
C<noextensions> are removed from the list of extensions to build, while
the C<onlyextensions> is rather more severe and builds only the listed
extensions.  The latter should be used with extreme caution since
certain extensions are used by many other extensions and modules:
examples of such modules include Fcntl and IO.  The order of processing
these options is first C<only> (if present), then C<no> (if present).

Of course, you may always run Configure interactively and select only
the extensions you want.

If you unpack any additional extensions in the ext/ directory before
running Configure, then Configure will offer to build those additional
extensions as well.  Most users probably shouldn't have to do this --
it is usually easier to build additional extensions later after perl
has been installed.  However, if you wish to have those additional
extensions statically linked into the perl binary, then this offers a
convenient way to do that in one step.  (It is not necessary, however;
you can build and install extensions just fine even if you don't have
dynamic loading.  See lib/ExtUtils/MakeMaker.pm for more details.)
Another way of specifying extra modules is described in
L<"Adding extra modules to the build"> below.

If you re-use an old config.sh but change your system (e.g. by
adding libgdbm) Configure will still offer your old choices of extensions
for the default answer, but it will also point out the discrepancy to
you.

=head2 Including locally-installed libraries

Perl comes with interfaces to number of libraries, including threads,
dbm, ndbm, gdbm, and Berkeley db.  For the *db* extension, if
Configure can find the appropriate header files and libraries, it will
automatically include that extension.  The threading extension needs
to be specified explicitly (see L</Threads>).

Those libraries are not distributed with perl. If your header (.h) files
for those libraries are not in a directory normally searched by your C
compiler, then you will need to include the appropriate -I/your/directory
option when prompted by Configure.  If your libraries are not in a
directory normally searched by your C compiler and linker, then you will
need to include the appropriate -L/your/directory option when prompted
by Configure. See the examples below.

=head3 Examples

=over 4

=item gdbm in /usr/local

Suppose you have gdbm and want Configure to find it and build the
GDBM_File extension.  This example assumes you have gdbm.h
installed in /usr/local/include/gdbm.h and libgdbm.a installed in
/usr/local/lib/libgdbm.a.  Configure should figure all the
necessary steps out automatically.

Specifically, when Configure prompts you for flags for
your C compiler, you should include -I/usr/local/include, if it's
not here yet. Similarly, when Configure prompts you for linker flags,
you should include -L/usr/local/lib.

If you are using dynamic loading, then when Configure prompts you for
linker flags for dynamic loading, you should again include
-L/usr/local/lib.

Again, this should all happen automatically.  This should also work if
you have gdbm installed in any of (/usr/local, /opt/local, /usr/gnu,
/opt/gnu, /usr/GNU, or /opt/GNU).

=item BerkeleyDB in /usr/local/BerkeleyDB

The version of BerkeleyDB distributed by Oracle installs in a
version-specific directory by default, typically something like
/usr/local/BerkeleyDB.4.7.  To have Configure find that, you need to add
-I/usr/local/BerkeleyDB.4.7/include to cc flags, as in the previous
example, and you will also have to take extra steps to help Configure
find -ldb.  Specifically, when Configure prompts you for library
directories, add /usr/local/BerkeleyDB.4.7/lib to the list.  Also, you
will need to add appropriate linker flags to tell the runtime linker
where to find the BerkeleyDB shared libraries.

It is possible to specify this from the command line (all on one
line):

 sh Configure -de \
    -Dlocincpth='/usr/local/BerkeleyDB.4.7/include             \
                                           /usr/local/include' \
    -Dloclibpth='/usr/local/BerkeleyDB.4.7/lib /usr/local/lib' \
    -Aldflags='-R/usr/local/BerkeleyDB.4.7/lib'

locincpth is a space-separated list of include directories to search.
Configure will automatically add the appropriate -I directives.

loclibpth is a space-separated list of library directories to search.
Configure will automatically add the appropriate -L directives.

The addition to ldflags is so that the dynamic linker knows where to find
the BerkeleyDB libraries.  For Linux and Solaris, the -R option does that.
Other systems may use different flags.  Use the appropriate flag for your
system.

=back

=head2 Specifying a logical root directory

If you are cross-compiling, or are using a compiler which has it's own
headers and libraries in a nonstandard location, and your compiler
understands the C<--sysroot> option, you can use the C<-Dsysroot> option
to specify the logical root directory under which all libraries and
headers are searched for. This patch adjusts Configure to search under
$sysroot, instead of /.

--sysroot is added to ccflags and friends so that make in
ExtUtils::MakeMaker, and other extensions, will use it.

=head2 Overriding an old config.sh

If you want to use an old config.sh produced by a previous run of
Configure, but override some of the items with command line options, you
need to use B<Configure -O>.

=head2 GNU-style configure

If you prefer the GNU-style configure command line interface, you can
use the supplied configure.gnu command, e.g.

	CC=gcc ./configure.gnu

The configure.gnu script emulates a few of the more common configure
options.  Try

	./configure.gnu --help

for a listing.

(The file is called configure.gnu to avoid problems on systems
that would not distinguish the files "Configure" and "configure".)

=head2 Malloc Issues

Perl relies heavily on malloc(3) to grow data structures as needed,
so perl's performance can be noticeably affected by the performance of
the malloc function on your system.  The perl source is shipped with a
version of malloc that has been optimized for the typical requests from
perl, so there's a chance that it may be both faster and use less memory
than your system malloc.

However, if your system already has an excellent malloc, or if you are
experiencing difficulties with extensions that use third-party libraries
that call malloc, then you should probably use your system's malloc.
(Or, you might wish to explore the malloc flags discussed below.)

=over 4

=item Using the system malloc

To build without perl's malloc, you can use the Configure command

	sh Configure -Uusemymalloc

or you can answer 'n' at the appropriate interactive Configure prompt.

Note that Perl's malloc isn't always used by default; that actually
depends on your system. For example, on Linux and FreeBSD (and many more
systems), Configure chooses to use the system's malloc by default.
See the appropriate file in the F<hints/> directory to see how the
default is set.

=item -DPERL_POLLUTE_MALLOC

NOTE: This flag is enabled automatically on some platforms if you just
run Configure to accept all the defaults.

Perl's malloc family of functions are normally called Perl_malloc(),
Perl_realloc(), Perl_calloc() and Perl_mfree().
These names do not clash with the system versions of these functions.

If this flag is enabled, however, Perl's malloc family of functions
will have the same names as the system versions.  This may be required
sometimes if you have libraries that like to free() data that may have
been allocated by Perl_malloc() and vice versa.

Note that enabling this option may sometimes lead to duplicate symbols
from the linker for malloc et al.  In such cases, the system probably
does not allow its malloc functions to be fully replaced with custom
versions.

=item -DPERL_DEBUGGING_MSTATS

This flag enables debugging mstats, which is required to use the
Devel::Peek::mstat() function. You cannot enable this unless you are
using Perl's malloc, so a typical Configure command would be

       sh Configure -Accflags=-DPERL_DEBUGGING_MSTATS -Dusemymalloc

to enable this option.

=back

=head2 What if it doesn't work?

If you run into problems, try some of the following ideas.
If none of them help, then see L<"Reporting Problems"> below.

=over 4

=item Running Configure Interactively

If Configure runs into trouble, remember that you can always run
Configure interactively so that you can check (and correct) its
guesses.

All the installation questions have been moved to the top, so you don't
have to wait for them.  Once you've handled them (and your C compiler and
flags) you can type  &-d  at the next Configure prompt and Configure
will use the defaults from then on.

If you find yourself trying obscure command line incantations and
config.over tricks, I recommend you run Configure interactively
instead.  You'll probably save yourself time in the long run.

=item Hint files

Hint files tell Configure about a number of things:

=over 4

=item o

The peculiarities or conventions of particular platforms -- non-standard
library locations and names, default installation locations for binaries,
and so on.

=item o

The deficiencies of the platform -- for example, library functions that,
although present, are too badly broken to be usable; or limits on
resources that are generously available on most platforms.

=item o

How best to optimize for the platform, both in terms of binary size
and/or speed, and for Perl feature support. Because of wide variations in
the implementation of shared libraries and of threading, for example,
Configure often needs hints in order to be able to use these features.

=back

The perl distribution includes many system-specific hints files
in the hints/ directory. If one of them matches your system, Configure
will offer to use that hint file. Unless you have a very good reason
not to, you should accept its offer.

Several of the hint files contain additional important information.
If you have any problems, it is a good idea to read the relevant hint
file for further information.  See hints/solaris_2.sh for an extensive
example.  More information about writing good hints is in the
hints/README.hints file, which also explains hint files known as
callback-units.

Note that any hint file is read before any Policy file, meaning that
Policy overrides hints -- see L</Site-wide Policy settings>.

=item WHOA THERE!!!

If you are re-using an old config.sh, it's possible that Configure
detects different values from the ones specified in this file.  You will
almost always want to keep the previous value, unless you have changed
something on your system.

For example, suppose you have added libgdbm.a to your system
and you decide to reconfigure perl to use GDBM_File.  When you run
Configure again, you will need to add -lgdbm to the list of libraries.
Now, Configure will find your gdbm include file and library and will
issue a message:

    *** WHOA THERE!!! ***
	The previous value for $i_gdbm on this machine was "undef"!
	Keep the previous value? [y]

In this case, you do not want to keep the previous value, so you
should answer 'n'.  (You'll also have to manually add GDBM_File to
the list of dynamic extensions to build.)

=item Changing Compilers

If you change compilers or make other significant changes, you should
probably not re-use your old config.sh.  Simply remove it or
rename it, then rerun Configure with the options you want to use.

=item Propagating your changes to config.sh

If you make any changes to config.sh, you should propagate
them to all the .SH files by running

	sh Configure -S

You will then have to rebuild by running

	make depend
	make

=item config.over and config.arch

You can also supply a shell script config.over to override
Configure's guesses.  It will get loaded up at the very end, just
before config.sh is created.  You have to be careful with this,
however, as Configure does no checking that your changes make sense.
This file is usually good for site-specific customizations.

There is also another file that, if it exists, is loaded before the
config.over, called config.arch.  This file is intended to be per
architecture, not per site, and usually it's the architecture-specific
hints file that creates the config.arch.

=item config.h

Many of the system dependencies are contained in config.h.
Configure builds config.h by running the config_h.SH script.
The values for the variables are taken from config.sh.

If there are any problems, you can edit config.h directly.  Beware,
though, that the next time you run Configure, your changes will be
lost.

=item cflags

If you have any additional changes to make to the C compiler command
line, they can be made in cflags.SH.  For instance, to turn off the
optimizer on toke.c, find the switch structure marked 'or customize here',
and add a line for toke.c ahead of the catch-all *) so that it now reads:

    : or customize here

    case "$file" in
    toke) optimize='-g' ;;
    *) ;;

You should not edit the generated file cflags directly, as your changes
will be lost the next time you run Configure, or if you edit config.sh.

To explore various ways of changing ccflags from within a hint file,
see the file hints/README.hints.

To change the C flags for all the files, edit config.sh and change either
$ccflags or $optimize, and then re-run

	sh Configure -S
	make depend

=item No sh

If you don't have sh, you'll have to copy the sample file
Porting/config.sh to config.sh and edit your config.sh to reflect your
system's peculiarities.  See Porting/pumpkin.pod for more information.
You'll probably also have to extensively modify the extension building
mechanism.

=item Porting information

Specific information for the OS/2, Plan 9, VMS and Win32 ports is in the
corresponding README files and subdirectories.  Additional information,
including a glossary of all those config.sh variables, is in the Porting
subdirectory.  Porting/Glossary should especially come in handy.

Ports for other systems may also be available.  You should check out
http://www.cpan.org/ports for current information on ports to
various other operating systems.

If you plan to port Perl to a new architecture, study carefully the
section titled "Philosophical Issues in Patching and Porting Perl"
in the file Porting/pumpkin.pod and the file pod/perlgit.pod.
Study also how other non-UNIX ports have solved problems.

=back

=head2 Adding extra modules to the build

You can specify extra modules or module bundles to be fetched from the
CPAN and installed as part of the Perl build.  Either use the -Dextras=...
command line parameter to Configure, for example like this:

	Configure -Dextras="Bundle::LWP DBI"

or answer first 'y' to the question 'Install any extra modules?' and
then answer "Bundle::LWP DBI" to the 'Extras?' question.
The module or the bundle names are as for the CPAN module 'install'
command.  This will only work if those modules are to be built as dynamic
extensions.  If you wish to include those extra modules as static
extensions, see L<"Extensions"> above.

Notice that because the CPAN module will be used to fetch the extra
modules, you will need access to the CPAN, either via the Internet,
or via a local copy such as a CD-ROM or a local CPAN mirror.  If you
do not, using the extra modules option will die horribly.

Also notice that you yourself are responsible for satisfying any extra
dependencies such as external headers or libraries BEFORE trying the
build.  For example: you will need to have the Foo database specific
headers and libraries installed for the DBD::Foo module.  The Configure
process or the Perl build process will not help you with these.

=head2 suidperl

suidperl was an optional component of earlier releases of perl. It is no
longer available.  Instead, use a tool specifically designed to handle
changes in privileges, such as B<sudo>.

=head1 make depend

This will look for all the includes.  The output is stored in makefile.
The only difference between Makefile and makefile is the dependencies at
the bottom of makefile.  If you have to make any changes, you should edit
makefile, not Makefile, since the Unix make command reads makefile first.
(On non-Unix systems, the output may be stored in a different file.
Check the value of $firstmakefile in your config.sh if in doubt.)

Configure will offer to do this step for you, so it isn't listed
explicitly above.

=head1 make

This will attempt to make perl in the current directory.

=head2 Expected errors

These error reports are normal, and can be ignored:

  ...
  make: [extra.pods] Error 1 (ignored)
  ...
  make: [extras.make] Error 1 (ignored)

=head2 What if it doesn't work?

If you can't compile successfully, try some of the following ideas.
If none of them help, and careful reading of the error message and
the relevant manual pages on your system doesn't help,
then see L<"Reporting Problems"> below.

=over 4

=item hints

If you used a hint file, try reading the comments in the hint file
for further tips and information.

=item extensions

If you can successfully build miniperl, but the process crashes
during the building of extensions, run

	make minitest

to test your version of miniperl.

=item locale

If you have any locale-related environment variables set, try unsetting
them.  I have some reports that some versions of IRIX hang while
running B<./miniperl configpm> with locales other than the C locale.
See the discussion under L<"make test"> below about locales and the
whole L<perllocale/"LOCALE PROBLEMS"> section in the file
pod/perllocale.pod.  The latter is especially useful if you see something
like this

	perl: warning: Setting locale failed.
	perl: warning: Please check that your locale settings:
	        LC_ALL = "En_US",
	        LANG = (unset)
	    are supported and installed on your system.
	perl: warning: Falling back to the standard locale ("C").

at Perl startup.

=item other environment variables

Configure does not check for environment variables that can sometimes
have a major influence on how perl is built or tested. For example,
OBJECT_MODE on AIX determines the way the compiler and linker deal with
their objects, but this is a variable that only influences build-time
behaviour, and should not affect the perl scripts that are eventually
executed by the perl binary. Other variables, like PERL_UNICODE,
PERL5LIB, and PERL5OPT will influence the behaviour of the test suite.
So if you are getting strange test failures, you may want to try
retesting with the various PERL variables unset.

=item varargs

If you get varargs problems with gcc, be sure that gcc is installed
correctly and that you are not passing -I/usr/include to gcc.  When using
gcc, you should probably have i_stdarg='define' and i_varargs='undef'
in config.sh.  The problem is usually solved by installing gcc
correctly.  If you do change config.sh, don't forget to propagate
your changes (see L<"Propagating your changes to config.sh"> below).
See also the L<"vsprintf"> item below.

=item util.c

If you get error messages such as the following (the exact line
numbers and function name may vary in different versions of perl):

    util.c: In function 'Perl_form':
    util.c:1107: number of arguments doesn't match prototype
    proto.h:125: prototype declaration

it might well be a symptom of the gcc "varargs problem".  See the
previous L<"varargs"> item.

=item LD_LIBRARY_PATH

If you run into dynamic loading problems, check your setting of
the LD_LIBRARY_PATH environment variable.  If you're creating a static
Perl library (libperl.a rather than libperl.so) it should build
fine with LD_LIBRARY_PATH unset, though that may depend on details
of your local setup.

=item nm extraction

If Configure seems to be having trouble finding library functions,
try not using nm extraction.  You can do this from the command line
with

	sh Configure -Uusenm

or by answering the nm extraction question interactively.
If you have previously run Configure, you should not reuse your old
config.sh.

=item umask not found

If the build processes encounters errors relating to umask(), the problem
is probably that Configure couldn't find your umask() system call.
Check your config.sh.  You should have d_umask='define'.  If you don't,
this is probably the L<"nm extraction"> problem discussed above.  Also,
try reading the hints file for your system for further information.

=item vsprintf

If you run into problems with vsprintf in compiling util.c, the
problem is probably that Configure failed to detect your system's
version of vsprintf().  Check whether your system has vprintf().
(Virtually all modern Unix systems do.)  Then, check the variable
d_vprintf in config.sh.  If your system has vprintf, it should be:

	d_vprintf='define'

If Configure guessed wrong, it is likely that Configure guessed wrong
on a number of other common functions too.  This is probably
the L<"nm extraction"> problem discussed above.

=item do_aspawn

If you run into problems relating to do_aspawn or do_spawn, the
problem is probably that Configure failed to detect your system's
fork() function.  Follow the procedure in the previous item
on L<"nm extraction">.

=item __inet_* errors

If you receive unresolved symbol errors during Perl build and/or test
referring to __inet_* symbols, check to see whether BIND 8.1 is
installed.  It installs a /usr/local/include/arpa/inet.h that refers to
these symbols.  Versions of BIND later than 8.1 do not install inet.h
in that location and avoid the errors.  You should probably update to a
newer version of BIND (and remove the files the old one left behind).
If you can't, you can either link with the updated resolver library
provided with BIND 8.1 or rename /usr/local/bin/arpa/inet.h during the
Perl build and test process to avoid the problem.

=item .*_r() prototype NOT found

On a related note, if you see a bunch of complaints like the above about
reentrant functions -- specifically networking-related ones -- being
present but without prototypes available, check to see if BIND 8.1 (or
possibly other BIND 8 versions) is (or has been) installed. They install
header files such as netdb.h into places such as /usr/local/include (or
into another directory as specified at build/install time), at least
optionally.  Remove them or put them in someplace that isn't in the C
preprocessor's header file include search path (determined by -I options
plus defaults, normally /usr/include).

=item #error "No DATAMODEL_NATIVE specified"

This is a common error when trying to build perl on Solaris 2.6 with a
gcc installation from Solaris 2.5 or 2.5.1.  The Solaris header files
changed, so you need to update your gcc installation.  You can either
rerun the fixincludes script from gcc or take the opportunity to
update your gcc installation.

=item Optimizer

If you can't compile successfully, try turning off your compiler's
optimizer.  Edit config.sh and change the line

	optimize='-O'

to

	optimize=' '

then propagate your changes with B<sh Configure -S> and rebuild
with B<make depend; make>.

=item Missing functions and Undefined symbols

If the build of miniperl fails with a long list of missing functions or
undefined symbols, check the libs variable in the config.sh file.  It
should look something like

	libs='-lsocket -lnsl -ldl -lm -lc'

The exact libraries will vary from system to system, but you typically
need to include at least the math library -lm.  Normally, Configure
will suggest the correct defaults.  If the libs variable is empty, you
need to start all over again.  Run

	make distclean

and start from the very beginning.  This time, unless you are sure of
what you are doing, accept the default list of libraries suggested by
Configure.

If the libs variable is missing -lm, there is a chance that libm.so.1
is available, but the required (symbolic) link to libm.so is missing.
(same could be the case for other libraries like libcrypt.so).  You
should check your installation for packages that create that link, and
if no package is installed that supplies that link or you cannot install
them, make the symbolic link yourself e.g.:

 $ rpm -qf /usr/lib64/libm.so
 glibc-devel-2.15-22.17.1.x86_64
 $ ls -lgo /usr/lib64/libm.so
 lrwxrwxrwx 1 16 Jan  7  2013 /usr/lib64/libm.so -> /lib64/libm.so.6

 or

 $ sudo ln -s /lib64/libm.so.6 /lib64/libm.so

If the libs variable looks correct, you might have the
L<"nm extraction"> problem discussed above.

If you still have missing routines or undefined symbols, you probably
need to add some library or other, make a symbolic link like described
above, or you need to undefine some feature that Configure thought was
there but is defective or incomplete.  If you used a hint file, see if
it has any relevant advice.  You can also look through through config.h
for likely suspects.

=item toke.c

Some compilers will not compile or optimize the larger files (such as
toke.c) without some extra switches to use larger jump offsets or
allocate larger internal tables.  You can customize the switches for
each file in cflags.SH.  It's okay to insert rules for specific files
into makefile since a default rule only takes effect in the absence of a
specific rule.

=item Missing dbmclose

SCO prior to 3.2.4 may be missing dbmclose().  An upgrade to 3.2.4
that includes libdbm.nfs (which includes dbmclose()) may be available.

=item error: too few arguments to function 'dbmclose'

Building ODBM_File on some (Open)SUSE distributions might run into this
error, as the header file is broken. There are two ways to deal with this

 1. Disable the use of ODBM_FILE

    Configure ... -Dnoextensions=ODBM_File

 2. Fix the header file, somewhat like this:

    --- a/usr/include/dbm.h  2010-03-24 08:54:59.000000000 +0100
    +++ b/usr/include/dbm.h  2010-03-24 08:55:15.000000000 +0100
    @@ -59,4 +59,4 @@ extern datum  firstkey __P((void));

     extern datum   nextkey __P((datum key));

    -extern int     dbmclose __P((DBM *));
    +extern int     dbmclose __P((void));

=item Warning (mostly harmless): No library found for -lsomething

If you see such a message during the building of an extension, but
the extension passes its tests anyway (see L<"make test"> below),
then don't worry about the warning message.  The extension
Makefile.PL goes looking for various libraries needed on various
systems; few systems will need all the possible libraries listed.
Most users will see warnings for the ones they don't have.  The
phrase 'mostly harmless' is intended to reassure you that nothing
unusual is happening, and the build process is continuing.

On the other hand, if you are building GDBM_File and you get the
message

    Warning (mostly harmless): No library found for -lgdbm

then it's likely you're going to run into trouble somewhere along
the line, since it's hard to see how you can use the GDBM_File
extension without the -lgdbm library.

It is true that, in principle, Configure could have figured all of
this out, but Configure and the extension building process are not
quite that tightly coordinated.

=item sh: ar: not found

This is a message from your shell telling you that the command 'ar'
was not found.  You need to check your PATH environment variable to
make sure that it includes the directory with the 'ar' command.  This
is a common problem on Solaris, where 'ar' is in the /usr/ccs/bin
directory.

=item db-recno failure on tests 51, 53 and 55

Old versions of the DB library (including the DB library which comes
with FreeBSD 2.1) had broken handling of recno databases with modified
bval settings.  Upgrade your DB library or OS.

=item Bad arg length for semctl, is XX, should be ZZZ

If you get this error message from the F<cpan/IPC-SysV/t/sem.t> test, your
System V IPC may be broken.  The XX typically is 20, and that is what ZZZ
also should be.  Consider upgrading your OS, or reconfiguring your OS
to include the System V semaphores.

=item cpan/IPC-SysV/t/sem........semget: No space left on device

Either your account or the whole system has run out of semaphores.  Or
both.  Either list the semaphores with "ipcs" and remove the unneeded
ones (which ones these are depends on your system and applications)
with "ipcrm -s SEMAPHORE_ID_HERE" or configure more semaphores to your
system.

=item GNU binutils

If you mix GNU binutils (nm, ld, ar) with equivalent vendor-supplied
tools you may be in for some trouble.  For example creating archives
with an old GNU 'ar' and then using a new current vendor-supplied 'ld'
may lead into linking problems.  Either recompile your GNU binutils
under your current operating system release, or modify your PATH not
to include the GNU utils before running Configure, or specify the
vendor-supplied utilities explicitly to Configure, for example by
Configure -Dar=/bin/ar.

=item THIS PACKAGE SEEMS TO BE INCOMPLETE

The F<Configure> program has not been able to find all the files which
make up the complete Perl distribution.  You may have a damaged source
archive file (in which case you may also have seen messages such as
C<gzip: stdin: unexpected end of file> and C<tar: Unexpected EOF on
archive file>), or you may have obtained a structurally-sound but
incomplete archive.  In either case, try downloading again from the
official site named at the start of this document.  If you do find
that any site is carrying a corrupted or incomplete source code
archive, please report it to the site's maintainer.

=item invalid token: ##

You are using a non-ANSI-compliant C compiler.  To compile Perl, you
need to use a compiler that supports ANSI C.  If there is a README
file for your system, it may have further details on your compiler
options.

=item Miscellaneous

Some additional things that have been reported:

Genix may need to use libc rather than libc_s, or #undef VARARGS.

NCR Tower 32 (OS 2.01.01) may need -W2,-Sl,2000 and #undef MKDIR.

UTS may need one or more of -K or -g, and #undef LSTAT.

FreeBSD can fail the F<cpan/IPC-SysV/t/sem.t> test if SysV IPC has not been
configured in the kernel.  Perl tries to detect this, though, and
you will get a message telling you what to do.

Building Perl on a system that has also BIND (headers and libraries)
installed may run into troubles because BIND installs its own netdb.h
and socket.h, which may not agree with the operating system's ideas of
the same files.  Similarly, including -lbind may conflict with libc's
view of the world.  You may have to tweak -Dlocincpth and -Dloclibpth
to avoid the BIND.

=back

=head2 Cross-compilation

Perl can be cross-compiled.  It is just not trivial, cross-compilation
rarely is.  Perl is routinely cross-compiled for several platforms: as of
January 2014, these include Android, Blackberry 10, PocketPC aka
WinCE, ARM Linux, and Solaris.  Previous versions of
Perl also provided support for Open Zaurus, Symbian, and
the IBM OS/400, but it's unknown if those ports are still functional.
These platforms are known as the B<target> platforms, while the systems
where the compilation takes place are the B<host> platforms.

What makes the situation difficult is that first of all,
cross-compilation environments vary significantly in how they are set
up and used, and secondly because the primary way of configuring Perl
(using the rather large Unix-tool-dependent Configure script) is not
awfully well suited for cross-compilation.  However, starting from
version 5.18.0, the Configure script also knows two ways of supporting
cross-compilation, so please keep reading.

See the following files for more information about compiling Perl for
the particular platforms:

=over 4

=item WinCE/PocketPC

L<README.ce or perlce|perlce>

=item Android

L<"Cross-compilation" in README.android or
perlandroid|perlandroid/Cross-compilation>

=item Blackberry

L<"Cross-compilation" in README.qnx or perlqnx|perlqnx/Cross-compilation>

=item Solaris

L<"CROSS-COMPILATION" in README.solaris or
perlsolaris|perlsolaris/CROSS-COMPILATION>

=item Linux

This document; See below.

=back

Packaging and transferring either the core Perl modules or CPAN
modules to the target platform is also left up to the each
cross-compilation environment.  Often the cross-compilation target
platforms are somewhat limited in diskspace: see the section
L<Minimizing the Perl installation> to learn more of the minimal set
of files required for a functional Perl installation.

For some cross-compilation environments the Configure option
C<-Dinstallprefix=...> might be handy, see L<Changing the installation
directory>.

About the cross-compilation support of Configure: There's two forms.
The more common one requires some way of transferring and running
executables in the target system, such as an ssh connection; this is the
C<./Configure -Dusecrosscompile -Dtargethost=...> route.  The second
method doesn't need access to the target system, but requires you to
provide a config.sh, and and a canned Makefile; the rest of this section
describes the former.

This cross-compilation setup of Configure has successfully been used in
a wide variety of setups, such as a 64-bit OS X host for an Android ARM
target, or an amd64 Linux host targeting x86 Solaris, or even Windows.

To run Configure in cross-compilation mode the basic switch that
has to be used is C<-Dusecrosscompile>:

   sh ./Configure -des -Dusecrosscompile -D...

This will make the cpp symbol USE_CROSS_COMPILE and the %Config
symbol C<usecrosscompile> available.

During the Configure and build, certain helper scripts will be created
into the Cross/ subdirectory.  The scripts are used to execute a
cross-compiled executable, and to transfer files to and from the
target host.  The execution scripts are named F<run-*> and the
transfer scripts F<to-*> and F<from-*>.  The part after the dash is
the method to use for remote execution and transfer: by default the
methods are B<ssh> and B<scp>, thus making the scripts F<run-ssh>,
F<to-scp>, and F<from-scp>.

To configure the scripts for a target host and a directory (in which
the execution will happen and which is to and from where the transfer
happens), supply Configure with

    -Dtargethost=so.me.ho.st -Dtargetdir=/tar/get/dir

The targethost is what e.g. ssh will use as the hostname, the targetdir
must exist (the scripts won't create it), the targetdir defaults to /tmp.
You can also specify a username to use for ssh/rsh logins

    -Dtargetuser=luser

but in case you don't, "root" will be used.  Similarly, you can specify
a non-standard (i.e. not 22) port for the connection, if applicable,
through

    -Dtargetport=2222

If the name of C<cc> has the usual GNU C semantics for cross
compilers, that is, CPU-OS-gcc, the target architecture (C<targetarch>),
plus names of the C<ar>, C<nm>, and C<ranlib> will also be automatically
chosen to be CPU-OS-ar and so on.
(The C<ld> requires more thought and will be chosen later by Configure
as appropriate).  This will also aid in guessing the proper
operating system name for the target, which has other repercussions, like
better defaults and possibly critical fixes for the platform.  If
Configure isn't guessing the OS name properly, you may need to either add
a hint file redirecting Configure's guess, or modify Configure to make
the correct choice.

If your compiler doesn't follow that convention, you will also need to
specify which target environment to use, as well as C<ar> and friends:

    -Dtargetarch=arm-linux
    -Dcc=mycrossgcc
    -Dar=...

Additionally, a cross-compilation toolchain will usually install it's own
logical system root somewhere -- that is, it'll create a directory
somewhere which includes subdirectories like C<'include'> or C<'lib'>.  For
example, you may end up with F</skiff/local/arm-linux>, where
F</skiff/local/arm-linux/bin> holds the binaries for cross-compilation,
F</skiff/local/arm-linux/include> has the headers, and
F</skiff/local/arm-linux/lib> has the library files.
If this is the case, and you are using a compiler that understands
C<--sysroot>, like gcc or clang, you'll want to specify the
C<-Dsysroot> option for Configure:

    -Dsysroot=/skiff/local/arm-linux

However, if your don't have a suitable directory to pass to C<-Dsysroot>,
you will also need to specify which target environment to use:

    -Dusrinc=/skiff/local/arm-linux/include
    -Dincpth=/skiff/local/arm-linux/include
    -Dlibpth=/skiff/local/arm-linux/lib

In addition to the default execution/transfer methods you can also
choose B<rsh> for execution, and B<rcp> or B<cp> for transfer,
for example:

    -Dtargetrun=rsh -Dtargetto=rcp -Dtargetfrom=cp

Putting it all together:

    sh ./Configure -des -Dusecrosscompile \
        -Dtargethost=so.me.ho.st \
        -Dtargetdir=/tar/get/dir \
        -Dtargetuser=root \
        -Dtargetarch=arm-linux \
        -Dcc=arm-linux-gcc \
        -Dsysroot=/skiff/local/arm-linux \
        -D...

or if you are happy with the defaults:

    sh ./Configure -des -Dusecrosscompile \
        -Dtargethost=so.me.ho.st \
        -Dcc=arm-linux-gcc \
        -D...

Another example where the cross-compiler has been installed under
F</usr/local/arm/2.95.5>:

    sh ./Configure -des -Dusecrosscompile \
        -Dtargethost=so.me.ho.st \
        -Dcc=/usr/local/arm/2.95.5/bin/arm-linux-gcc \
        -Dsysroot=/usr/local/arm/2.95.5

There is also a C<targetenv> option for Configure which can be used
to modify the environment of the target just before testing begins
during 'make test'.  For example, if the target system has a nonstandard
/tmp location, you could do this:

    -Dtargetenv="export TMPDIR=/other/tmp;"

If you are planning on cross-compiling to several platforms, or some
other thing that would involve running Configure several times, there are
two options that can be used to speed things up considerably.
As a bit of background, when you
call Configure with C<-Dusecrosscompile>, it begins by actually partially
building a miniperl on the host machine, as well as the generate_uudmap
binary, and we end up using that during the build.
So instead of building that new perl every single time, you can build it
just once in a separate directory, and then pass the resulting binaries
to Configure like this:

    -Dhostperl=/path/to/second/build/dir/miniperl
    -Dhostgenerate=/path/to/second/build/dir/generate_uudmap

Much less commonly, if you are cross-compiling from an ASCII host to an
EBCDIC target, or vise versa, you'll have to pass C<-Uhostgenerate> to
Configure, to signify that you want to build a generate_uudmap binary
that, during make, will be run on the target system.

=head1 make test

This will run the regression tests on the perl you just made.  If
'make test' doesn't say "All tests successful" then something went
wrong.

Note that you can't run the tests in background if this disables
opening of /dev/tty. You can use 'make test-notty' in that case but
a few tty tests will be skipped.

=head2 What if make test doesn't work?

If make test bombs out, just cd to the t directory and run ./TEST
by hand to see if it makes any difference.

One way to get more detailed information about failed tests and
individual subtests is to run the harness from the t directory:

	cd t ; ./perl harness <list of tests>

(this assumes that most basic tests succeed, since harness uses
complicated constructs). If no list of tests is provided, harness
will run all tests.

If individual tests fail, you can often run them by hand (from the main
perl directory), e.g.,

	./perl -MTestInit t/op/groups.t

You should also read the individual tests to see if there are any helpful
comments that apply to your system.  You may also need to setup your
shared library path if you get errors like:

	/sbin/loader: Fatal Error: cannot map libperl.so

The file t/README in the t subdirectory contains more information about
running and modifying tests.

See L</"Building a shared Perl library"> earlier in this document.

=over 4

=item locale

Note:  One possible reason for errors is that some external programs
may be broken due to the combination of your environment and the way
'make test' exercises them.  For example, this may happen if you have
one or more of these environment variables set:  LC_ALL LC_CTYPE
LC_COLLATE LANG.  In some versions of UNIX, the non-English locales
are known to cause programs to exhibit mysterious errors.

If you have any of the above environment variables set, please try

	setenv LC_ALL C

(for C shell) or

	LC_ALL=C;export LC_ALL

for Bourne or Korn shell) from the command line and then retry
make test.  If the tests then succeed, you may have a broken program that
is confusing the testing.  Please run the troublesome test by hand as
shown above and see whether you can locate the program.  Look for
things like:  exec, `backquoted command`, system, open("|...") or
open("...|").  All these mean that Perl is trying to run some
external program.

=item Timing problems

Several tests in the test suite check timing functions, such as
sleep(), and see if they return in a reasonable amount of time.
If your system is quite busy and doesn't respond quickly enough,
these tests might fail.  If possible, try running the tests again
with the system under a lighter load.  These timing-sensitive
and load-sensitive tests include F<t/op/alarm.t>,
F<dist/Time-HiRes/t/alarm.t>, F<dist/Time-HiRes/t/clock.t>,
F<dist/Time-HiRes/t/itimer.t>, F<dist/Time-HiRes/t/usleep.t>,
F<dist/threads-shared/t/waithires.t>,
F<dist/threads-shared/t/stress.t>, F<lib/Benchmark.t>,
F<lib/Memoize/t/expmod_t.t>, and F<lib/Memoize/t/speed.t>.

You might also experience some failures in F<t/op/stat.t> if you build
perl on an NFS filesystem, if the remote clock and the system clock are
different.

=item Out of memory

On some systems, particularly those with smaller amounts of RAM, some
of the tests in t/op/pat.t may fail with an "Out of memory" message.
For example, on my SparcStation IPC with 12 MB of RAM, in perl5.5.670,
test 85 will fail if run under either t/TEST or t/harness.

Try stopping other jobs on the system and then running the test by itself:

	./perl -MTestInit t/op/pat.t

to see if you have any better luck.  If your perl still fails this
test, it does not necessarily mean you have a broken perl.  This test
tries to exercise the regular expression subsystem quite thoroughly,
and may well be far more demanding than your normal usage.

=item libgcc_s.so.1: cannot open shared object file

This message has been reported on gcc-3.2.3 and earlier installed with
a non-standard prefix.  Setting the LD_LIBRARY_PATH environment variable
(or equivalent) to include gcc's lib/ directory with the libgcc_s.so.1
shared library should fix the problem.

=item Failures from lib/File/Temp/t/security saying "system possibly insecure"

First, such warnings are not necessarily serious or indicative of a
real security threat.  That being said, they bear investigating.

Note that each of the tests is run twice.  The first time is in the
directory returned by File::Spec->tmpdir() (often /tmp on Unix
systems), and the second time in the directory from which the test was
run (usually the 't' directory, if the test was run as part of 'make
test').

The tests may fail for the following reasons:

(1) If the directory the tests are being run in is owned by somebody
other than the user running the tests, or by root (uid 0).

This failure can happen if the Perl source code distribution is
unpacked in such a way that the user IDs in the distribution package
are used as-is.  Some tar programs do this.

(2) If the directory the tests are being run in is writable by group or
by others, and there is no sticky bit set for the directory.  (With
UNIX/POSIX semantics, write access to a directory means the right to
add or remove files in that directory.  The 'sticky bit' is a feature
used in some UNIXes to give extra protection to files: if the bit is
set for a directory, no one but the owner (or root) can remove that
file even if the permissions would otherwise allow file removal by
others.)

This failure may or may not be a real problem: it depends on the
permissions policy used on this particular system.  This failure can
also happen if the system either doesn't support the sticky bit (this
is the case with many non-UNIX platforms: in principle File::Temp
should know about these platforms and skip the tests), or if the system
supports the sticky bit but for some reason or reasons it is not being
used.  This is, for example, the case with HP-UX: as of HP-UX release
11.00, the sticky bit is very much supported, but HP-UX doesn't use it
on its /tmp directory as shipped.  Also, as with the permissions, some
local policy might dictate that the stickiness is not used.

(3) If the system supports the POSIX 'chown giveaway' feature and if
any of the parent directories of the temporary file back to the root
directory are 'unsafe', using the definitions given above in (1) and
(2).  For Unix systems, this is usually not an issue if you are
building on a local disk.  See the documentation for the File::Temp
module for more information about 'chown giveaway'.

See the documentation for the File::Temp module for more information
about the various security aspects of temporary files.

=back

The core distribution can now run its regression tests in parallel on
Unix-like platforms. Instead of running C<make test>, set C<TEST_JOBS>
in your environment to the number of tests to run in parallel, and run
C<make test_harness>. On a Bourne-like shell, this can be done as

    TEST_JOBS=3 make test_harness  # Run 3 tests in parallel

An environment variable is used, rather than parallel make itself,
because L<TAP::Harness> needs to be able to schedule individual
non-conflicting test scripts itself, and there is no standard interface
to C<make> utilities to interact with their job schedulers.

=head1 make install

This will put perl into the public directory you specified to
Configure; by default this is /usr/local/bin.  It will also try to put
the man pages in a reasonable place.  It will not nroff the man pages,
however.  You may need to be root to run B<make install>.  If you are not
root, you must still have permission to install into the directories
in question and you should ignore any messages about chown not working.

If "make install" just says "'install' is up to date" or something
similar, you may be on a case-insensitive filesystems such as Mac's HFS+,
and you should say "make install-all".  (This confusion is brought to you
by the Perl distribution having a file called INSTALL.)

=head2 Installing perl under different names

If you want to install perl under a name other than "perl" (for example,
when installing perl with special features enabled, such as debugging),
indicate the alternate name on the "make install" line, such as:

    make install PERLNAME=myperl

You can separately change the base used for versioned names (like
"perl5.8.9") by setting PERLNAME_VERBASE, like

    make install PERLNAME=perl5 PERLNAME_VERBASE=perl

This can be useful if you have to install perl as "perl5" (e.g. to avoid
conflicts with an ancient version in /usr/bin supplied by your vendor).
Without this the versioned binary would be called "perl55.8.8".

=head2 Installing perl under a different directory

You can install perl under a different destination directory by using
the DESTDIR variable during C<make install>, with a command like

	make install DESTDIR=/tmp/perl5

DESTDIR is automatically prepended to all the installation paths.  See
the example in L<"DESTDIR"> above.

=head2 Installed files

If you want to see exactly what will happen without installing
anything, you can run

	./perl installperl -n
	./perl installman -n

make install will install the following:

    binaries

	perl,
	    perl5.n.n	where 5.n.n is the current release number.  This
			will be a link to perl.

    scripts

	cppstdin	This is used by the deprecated switch perl -P,
			if your cc -E can't read from stdin.
	c2ph, pstruct	Scripts for handling C structures in header
                        files.
	corelist	Shows versions of modules that come with
                        different
			versions of perl.
	cpan		The CPAN shell.
	enc2xs		Encoding module generator.
	h2ph		Extract constants and simple macros from C
                        headers.
	h2xs		Converts C .h header files to Perl extensions.
	instmodsh	A shell to examine installed modules.
	libnetcfg	Configure libnet.
	perlbug		Tool to report bugs in Perl.
	perldoc		Tool to read perl's pod documentation.
	perlivp		Perl Installation Verification Procedure.
	piconv		A Perl implementation of the encoding conversion
			utility iconv.
	pl2pm		Convert Perl 4 .pl files to Perl 5 .pm modules.
	pod2html,	Converters from perl's pod documentation format
	pod2man,
	pod2text,
	pod2usage
	podchecker	POD syntax checker.
	podselect	Prints sections of POD documentation.
	prove		A command-line tool for running tests.
	psed		A Perl implementation of sed.
	ptar		A Perl implementation of tar.
	ptardiff	A diff for tar archives.
	ptargrep	A grep for tar archives.
	shasum		A tool to print or check SHA checksums.
	splain		Describe Perl warnings and errors.
	xsubpp		Compiler to convert Perl XS code into C code.
	zipdetails	display the internal structure of zip files

    library files

			in $privlib and $archlib specified to
			Configure, usually under /usr/local/lib/perl5/.

    documentation

	man pages	in $man1dir, usually /usr/local/man/man1.
	module man
	pages		in $man3dir, usually /usr/local/man/man3.
	pod/*.pod	in $privlib/pod/.

installperl will also create the directories listed above
in L<"Installation Directories">.

Perl's *.h header files and the libperl library are also installed
under $archlib so that any user may later build new modules, run the
optional Perl compiler, or embed the perl interpreter into another
program even if the Perl source is no longer available.

=head2 Installing only version-specific parts

Sometimes you only want to install the version-specific parts of the perl
installation.  For example, you may wish to install a newer version of
perl alongside an already installed production version without
disabling installation of new modules for the production version.
To only install the version-specific parts of the perl installation, run

	Configure -Dversiononly

or answer 'y' to the appropriate Configure prompt.  Alternatively,
you can just manually run

	./perl installperl -v

and skip installman altogether.

See also L<"Maintaining completely separate versions"> for another
approach.

=head1 cd /usr/include; h2ph *.h sys/*.h

Some perl scripts need to be able to obtain information from the
system header files.  This command will convert the most commonly used
header files in /usr/include into files that can be easily interpreted
by perl.  These files will be placed in the architecture-dependent
library ($archlib) directory you specified to Configure.

Note: Due to differences in the C and perl languages, the conversion
of the header files is not perfect.  You will probably have to
hand-edit some of the converted files to get them to parse correctly.
For example, h2ph breaks spectacularly on type casting and certain
structures.

=head1 installhtml --help

Some sites may wish to make perl documentation available in HTML
format.  The installhtml utility can be used to convert pod
documentation into linked HTML files and install them.

Currently, the supplied ./installhtml script does not make use of the
html Configure variables.  This should be fixed in a future release.

The following command-line is an example of one used to convert
perl documentation:

  ./installhtml                   \
      --podroot=.                 \
      --podpath=lib:ext:pod:vms   \
      --recurse                   \
      --htmldir=/perl/nmanual     \
      --htmlroot=/perl/nmanual    \
      --splithead=pod/perlipc     \
      --splititem=pod/perlfunc    \
      --verbose

See the documentation in installhtml for more details.  It can take
many minutes to execute a large installation and you should expect to
see warnings like "no title", "unexpected directive" and "cannot
resolve" as the files are processed. We are aware of these problems
(and would welcome patches for them).

You may find it helpful to run installhtml twice. That should reduce
the number of "cannot resolve" warnings.

=head1 cd pod && make tex && (process the latex files)

Some sites may also wish to make the documentation in the pod/ directory
available in TeX format.  Type

	(cd pod && make tex && <process the latex files>)

=head1 Starting all over again

If you wish to rebuild perl from the same build directory, you should
clean it out with the command

	make distclean

or

	make realclean

The only difference between the two is that make distclean also removes
your old config.sh and Policy.sh files.  (A plain 'make clean' is now
eqivalent to 'make realclean'.)

If you are upgrading from a previous version of perl, or if you
change systems or compilers or make other significant changes, or if
you are experiencing difficulties building perl, you should not reuse
your old config.sh.

If your reason to reuse your old config.sh is to save your particular
installation choices, then you can probably achieve the same effect by
using the Policy.sh file.  See the section on L<"Site-wide Policy
settings"> above.

=head1 Reporting Problems

Wherever possible please use the perlbug tool supplied with this Perl
to report problems, as it automatically includes summary configuration
information about your perl, which may help us track down problems far
more quickly. But first you should read the advice in this file,
carefully re-read the error message and check the relevant manual pages
on your system, as these may help you find an immediate solution.  If
you are not sure whether what you are seeing is a bug, you can send a
message describing the problem to the comp.lang.perl.misc newsgroup to
get advice.

The perlbug tool is installed along with perl, so after you have
completed C<make install> it should be possible to run it with plain
C<perlbug>.  If the install fails, or you want to report problems with
C<make test> without installing perl, then you can use C<make nok> to
run perlbug to report the problem, or run it by hand from this source
directory with C<./perl -Ilib utils/perlbug>

If the build fails too early to run perlbug uninstalled, then please
B<run> the C<./myconfig> shell script, and mail its output along with
an accurate description of your problem to perlbug@perl.org

If Configure itself fails, and does not generate a config.sh file
(needed to run C<./myconfig>), then please mail perlbug@perl.org the
description of how Configure fails along with details of your system
-- for example the output from running C<uname -a>

Please try to make your message brief but clear.  Brief, clear bug
reports tend to get answered more quickly.  Please don't worry if your
written English is not great -- what matters is how well you describe
the important technical details of the problem you have encountered,
not whether your grammar and spelling is flawless.

Trim out unnecessary information.  Do not include large files (such as
config.sh or a complete Configure or make log) unless absolutely
necessary.  Do not include a complete transcript of your build
session.  Just include the failing commands, the relevant error
messages, and whatever preceding commands are necessary to give the
appropriate context.  Plain text should usually be sufficient -- fancy
attachments or encodings may actually reduce the number of people who
read your message.  Your message will get relayed to over 400
subscribers around the world so please try to keep it brief but clear.

If the bug you are reporting has security implications which make it
inappropriate to send to a publicly archived mailing list, then see
L<perlsec/SECURITY VULNERABILITY CONTACT INFORMATION>
for details of how to report the issue.

If you are unsure what makes a good bug report please read "How to
report Bugs Effectively" by Simon Tatham:
http://www.chiark.greenend.org.uk/~sgtatham/bugs.html

=head1 Coexistence with earlier versions of perl 5

Perl 5.24.1 is not binary compatible with earlier versions of Perl.
In other words, you will have to recompile your XS modules.

In general, you can usually safely upgrade from one version of Perl
(e.g.  5.X.Y) to another similar minor version (e.g. 5.X.(Y+1))) without
re-compiling all of your extensions.  You can also safely leave the old
version around in case the new version causes you problems for some
reason.

Usually, most extensions will probably not need to be recompiled to be
used with a newer version of Perl.  Here is how it is supposed to work.
(These examples assume you accept all the Configure defaults.)

Suppose you already have version 5.8.7 installed.  The directories
searched by 5.8.7 are typically like:

	/usr/local/lib/perl5/5.8.7/$archname
	/usr/local/lib/perl5/5.8.7
	/usr/local/lib/perl5/site_perl/5.8.7/$archname
	/usr/local/lib/perl5/site_perl/5.8.7

Now, suppose you install version 5.8.8.  The directories
searched by version 5.8.8 will be:

	/usr/local/lib/perl5/5.8.8/$archname
	/usr/local/lib/perl5/5.8.8
	/usr/local/lib/perl5/site_perl/5.8.8/$archname
	/usr/local/lib/perl5/site_perl/5.8.8

	/usr/local/lib/perl5/site_perl/5.8.7/$archname
	/usr/local/lib/perl5/site_perl/5.8.7
	/usr/local/lib/perl5/site_perl/

Notice the last three entries -- Perl understands the default structure
of the $sitelib directories and will look back in older, compatible
directories.  This way, modules installed under 5.8.7 will continue
to be usable by 5.8.7 but will also accessible to 5.8.8.  Further,
suppose that you upgrade a module to one which requires features
present only in 5.8.8.  That new module will get installed into
/usr/local/lib/perl5/site_perl/5.8.8 and will be available to 5.8.8,
but will not interfere with the 5.8.7 version.

The last entry, /usr/local/lib/perl5/site_perl/, is there so that
5.6.0 and above will look for 5.004-era pure perl modules.

Lastly, suppose you now install 5.10.0, which is not binary compatible
with 5.8.x.  The directories searched by 5.10.0 (if you don't change the
Configure defaults) will be:

	/usr/local/lib/perl5/5.10.0/$archname
	/usr/local/lib/perl5/5.10.0
	/usr/local/lib/perl5/site_perl/5.10.0/$archname
	/usr/local/lib/perl5/site_perl/5.10.0

	/usr/local/lib/perl5/site_perl/5.8.8

	/usr/local/lib/perl5/site_perl/5.8.7

	/usr/local/lib/perl5/site_perl/

Note that the earlier $archname entries are now gone, but pure perl
modules from earlier versions will still be found.

This way, you can choose to share compatible extensions, but also upgrade
to a newer version of an extension that may be incompatible with earlier
versions, without breaking the earlier versions' installations.

=head2 Maintaining completely separate versions

Many users prefer to keep all versions of perl in completely
separate directories.  This guarantees that an update to one version
won't interfere with another version.  (The defaults guarantee this for
libraries after 5.6.0, but not for executables. TODO?)  One convenient
way to do this is by using a separate prefix for each version, such as

	sh Configure -Dprefix=/opt/perl5.24.1

and adding /opt/perl5.24.1/bin to the shell PATH variable.  Such users
may also wish to add a symbolic link /usr/local/bin/perl so that
scripts can still start with #!/usr/local/bin/perl.

Others might share a common directory for maintenance sub-versions
(e.g. 5.10 for all 5.10.x versions), but change directory with
each major version.

If you are installing a development subversion, you probably ought to
seriously consider using a separate directory, since development
subversions may not have all the compatibility wrinkles ironed out
yet.

=head2 Upgrading from v5.22 or earlier

B<Perl 5.24.1 may not be binary compatible with Perl v5.22 or
earlier Perl releases.>  Perl modules having binary parts
(meaning that a C compiler is used) will have to be recompiled to be
used with 5.24.1.  If you find you do need to rebuild an extension with
5.24.1, you may safely do so without disturbing the older
installations.  (See L<"Coexistence with earlier versions of perl 5">
above.)

See your installed copy of the perllocal.pod file for a (possibly
incomplete) list of locally installed modules.  Note that you want
perllocal.pod, not perllocale.pod, for installed module information.

=head1 Minimizing the Perl installation

The following section is meant for people worrying about squeezing the
Perl installation into minimal systems (for example when installing
operating systems, or in really small filesystems).

Leaving out as many extensions as possible is an obvious way:
Encode, with its big conversion tables, consumes a lot of
space.  On the other hand, you cannot throw away everything.  The
Fcntl module is pretty essential.  If you need to do network
programming, you'll appreciate the Socket module, and so forth: it all
depends on what do you need to do.

In the following we offer two different slimmed down installation
recipes.  They are informative, not normative: the choice of files
depends on what you need.

Firstly, the bare minimum to run this script

  use strict;
  use warnings;
  foreach my $f (</*>) {
     print("$f\n");
  }

in Linux with perl-5.24.1 is as follows (under $Config{prefix}):

  ./bin/perl
  ./lib/perl5/5.24.1/strict.pm
  ./lib/perl5/5.24.1/warnings.pm
  ./lib/perl5/5.24.1/i686-linux/File/Glob.pm
  ./lib/perl5/5.24.1/feature.pm
  ./lib/perl5/5.24.1/XSLoader.pm
  ./lib/perl5/5.24.1/i686-linux/auto/File/Glob/Glob.so

Secondly, for perl-5.10.1, the Debian perl-base package contains 591
files, (of which 510 are for lib/unicore) totaling about 3.5MB in its
i386 version.  Omitting the lib/unicore/* files for brevity, the
remaining files are:

  /usr/bin/perl
  /usr/bin/perl5.10.1
  /usr/lib/perl/5.10.1/Config.pm
  /usr/lib/perl/5.10.1/Config_git.pl
  /usr/lib/perl/5.10.1/Config_heavy.pl
  /usr/lib/perl/5.10.1/Cwd.pm
  /usr/lib/perl/5.10.1/DynaLoader.pm
  /usr/lib/perl/5.10.1/Errno.pm
  /usr/lib/perl/5.10.1/Fcntl.pm
  /usr/lib/perl/5.10.1/File/Glob.pm
  /usr/lib/perl/5.10.1/Hash/Util.pm
  /usr/lib/perl/5.10.1/IO.pm
  /usr/lib/perl/5.10.1/IO/File.pm
  /usr/lib/perl/5.10.1/IO/Handle.pm
  /usr/lib/perl/5.10.1/IO/Pipe.pm
  /usr/lib/perl/5.10.1/IO/Seekable.pm
  /usr/lib/perl/5.10.1/IO/Select.pm
  /usr/lib/perl/5.10.1/IO/Socket.pm
  /usr/lib/perl/5.10.1/IO/Socket/INET.pm
  /usr/lib/perl/5.10.1/IO/Socket/UNIX.pm
  /usr/lib/perl/5.10.1/List/Util.pm
  /usr/lib/perl/5.10.1/POSIX.pm
  /usr/lib/perl/5.10.1/Scalar/Util.pm
  /usr/lib/perl/5.10.1/Socket.pm
  /usr/lib/perl/5.10.1/XSLoader.pm
  /usr/lib/perl/5.10.1/auto/Cwd/Cwd.so
  /usr/lib/perl/5.10.1/auto/DynaLoader/autosplit.ix
  /usr/lib/perl/5.10.1/auto/DynaLoader/dl_expandspec.al
  /usr/lib/perl/5.10.1/auto/DynaLoader/dl_find_symbol_anywhere.al
  /usr/lib/perl/5.10.1/auto/DynaLoader/dl_findfile.al
  /usr/lib/perl/5.10.1/auto/Fcntl/Fcntl.so
  /usr/lib/perl/5.10.1/auto/File/Glob/Glob.so
  /usr/lib/perl/5.10.1/auto/Hash/Util/Util.so
  /usr/lib/perl/5.10.1/auto/IO/IO.so
  /usr/lib/perl/5.10.1/auto/List/Util/Util.so
  /usr/lib/perl/5.10.1/auto/POSIX/POSIX.so
  /usr/lib/perl/5.10.1/auto/POSIX/autosplit.ix
  /usr/lib/perl/5.10.1/auto/POSIX/load_imports.al
  /usr/lib/perl/5.10.1/auto/Socket/Socket.so
  /usr/lib/perl/5.10.1/lib.pm
  /usr/lib/perl/5.10.1/re.pm
  /usr/share/doc/perl/AUTHORS.gz
  /usr/share/doc/perl/Documentation
  /usr/share/doc/perl/README.Debian
  /usr/share/doc/perl/changelog.Debian.gz
  /usr/share/doc/perl/copyright
  /usr/share/lintian/overrides/perl-base
  /usr/share/man/man1/perl.1.gz
  /usr/share/man/man1/perl5.10.1.1.gz
  /usr/share/perl/5.10.1/AutoLoader.pm
  /usr/share/perl/5.10.1/Carp.pm
  /usr/share/perl/5.10.1/Carp/Heavy.pm
  /usr/share/perl/5.10.1/Exporter.pm
  /usr/share/perl/5.10.1/Exporter/Heavy.pm
  /usr/share/perl/5.10.1/File/Spec.pm
  /usr/share/perl/5.10.1/File/Spec/Unix.pm
  /usr/share/perl/5.10.1/FileHandle.pm
  /usr/share/perl/5.10.1/Getopt/Long.pm
  /usr/share/perl/5.10.1/IPC/Open2.pm
  /usr/share/perl/5.10.1/IPC/Open3.pm
  /usr/share/perl/5.10.1/SelectSaver.pm
  /usr/share/perl/5.10.1/Symbol.pm
  /usr/share/perl/5.10.1/Text/ParseWords.pm
  /usr/share/perl/5.10.1/Text/Tabs.pm
  /usr/share/perl/5.10.1/Text/Wrap.pm
  /usr/share/perl/5.10.1/Tie/Hash.pm
  /usr/share/perl/5.10.1/attributes.pm
  /usr/share/perl/5.10.1/base.pm
  /usr/share/perl/5.10.1/bytes.pm
  /usr/share/perl/5.10.1/bytes_heavy.pl
  /usr/share/perl/5.10.1/constant.pm
  /usr/share/perl/5.10.1/fields.pm
  /usr/share/perl/5.10.1/integer.pm
  /usr/share/perl/5.10.1/locale.pm
  /usr/share/perl/5.10.1/overload.pm
  /usr/share/perl/5.10.1/strict.pm
  /usr/share/perl/5.10.1/unicore/*
  /usr/share/perl/5.10.1/utf8.pm
  /usr/share/perl/5.10.1/utf8_heavy.pl
  /usr/share/perl/5.10.1/vars.pm
  /usr/share/perl/5.10.1/warnings.pm
  /usr/share/perl/5.10.1/warnings/register.pm

A nice trick to find out the minimal set of Perl library files you will
need to run a Perl program is

   perl -e 'do "prog.pl"; END { print "$_\n" for sort keys %INC }'

(this will not find libraries required in runtime, unfortunately, but
it's a minimal set) and if you want to find out all the files you can
use something like the below

 strace perl -le 'do "x.pl"' 2>&1 \
                             | perl -nle '/^open\(\"(.+?)"/ && print $1'

(The 'strace' is Linux-specific, other similar utilities include 'truss'
and 'ktrace'.)

=head2 C<-DNO_MATHOMS>

If you configure perl with C<-Accflags=-DNO_MATHOMS>, the functions from
F<mathoms.c> will not be compiled in. Those functions are no longer used
by perl itself; for source compatibility reasons, though, they weren't
completely removed.

=head1 DOCUMENTATION

Read the manual entries before running perl.  The main documentation
is in the pod/ subdirectory and should have been installed during the
build process.  Type B<man perl> to get started.  Alternatively, you
can type B<perldoc perl> to use the supplied perldoc script.  This is
sometimes useful for finding things in the library modules.

=head1 AUTHOR

Original author:  Andy Dougherty doughera@lafayette.edu , borrowing very
heavily from the original README by Larry Wall, with lots of helpful
feedback and additions from the perl5-porters@perl.org folks.

If you have problems, corrections, or questions, please see
L<"Reporting Problems"> above.

=head1 REDISTRIBUTION

This document is part of the Perl package and may be distributed under
the same terms as perl itself, with the following additional request:
If you are distributing a modified version of perl (perhaps as part of
a larger package) please B<do> modify these installation instructions
and the contact information to match your distribution.