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
|
<!doctype HTML public "-//W3C//DTD HTML 4.0 Frameset//EN">
<html>
<head>
<title>Chapter 9: HDF5 Error Handling</title>
<!--(Meta)==========================================================-->
<!--(Links)=========================================================-->
<!--( Begin styles definition )=====================================-->
<link href="ed_styles/NewUGelect.css" rel="stylesheet" type="text/css">
<!--( End styles definition )=======================================-->
</head>
<body>
<!-- #BeginLibraryItem "/ed_libs/Copyright.lbi" -->
<!--
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
* Copyright by The HDF Group. *
* Copyright by the Board of Trustees of the University of Illinois. *
* All rights reserved. *
* *
* This file is part of HDF5. The full HDF5 copyright notice, including *
* terms governing use, modification, and redistribution, is contained in *
* the files COPYING and Copyright.html. COPYING can be found at the root *
* of the source code distribution tree; Copyright.html can be found at the *
* root level of an installed copy of the electronic HDF5 document set and *
* is linked from the top-level documents page. It can also be found at *
* http://www.hdfgroup.org/HDF5/doc/Copyright.html. If you do not have *
* access to either file, you may request a copy from help@hdfgroup.org. *
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
-->
<!-- #EndLibraryItem --><!--( TOC )=========================================================-->
<SCRIPT language="JavaScript">
<!--
document.writeln ('\
<table x-use-null-cells\
align="right"\
width="240"\
cellspacing="0"\
class="tocTable">\
<tr valign="top"> \
<td class="tocTableHeaderCell" colspan="2"> \
<span class="TableHead">Chapter Contents</span></td>\
</tr>\
-->
<!-- Table Version 3 -->\
<!--
<tr valign="top"> \
<td class="tocTableContentCell2"> \
<a href="#Intro">1.</a></td>\
<td class="tocTableContentCell3">\
<a href="#Intro">Introduction</a></td> \
</tr>\
<tr valign="top"> \
<td class="tocTableContentCell2"> \
<a href="#ProgModel">2.</a></td>\
<td class="tocTableContentCell3">\
<a href="#ProgModel">Programming Model</a></td>\
</tr>\
<tr valign="top"> \
<td class="tocTableContentCell2"> \
<a href="#ErrorHandling">3.</a></td>\
<td class="tocTableContentCell3">\
<a href="#ErrorHandling">Error Handling (H5E) Function Summaries</a></td> \
</tr>\
<tr valign="top"> \
<td class="tocTableContentCell2"> \
<a href="#BasicErrorHandling">4.</a></td>\
<td class="tocTableContentCell3">\
<a href="#BasicErrorHandling">Basic Error Handling Operations</a>\
</td>\
</tr>\
<tr valign="top">\
<td class="tocTableContentCell">\
<a href="#AdvancedErrorHandling">5.</a></td>\
<td class="tocTableContentCell4">\
<a href="#AdvancedErrorHandling">Advanced Error Handling Operations</a>\
</td>\
\
-->
<!-- editingComment -- "tocTableContentCell" and "tocTableContentCell4" \
-->\
<!-- are the table-closing cell class.\
-->\
<!--
\
</table>\
')
-->
</SCRIPT>
<!--(End TOC)=======================================================-->
<!-- HEADER LEFT "HDF5 User's Guide" -->
<!-- HEADER RIGHT "HDF5 Error Handling" -->
<div align="center">
<a name="TOP">
<h2>Chapter 9<br><font size="7">HDF5 Error Handling</font></h2>
</a>
</div>
<a name="Intro">
<h3>9.1. Introduction</h3>
</a>
<p>The HDF5 Library provides an error reporting mechanism for both
the library itself and for user application programs. It can trace
errors through function stack and error information like file name,
function name, line number, and error description. </p>
<p>Section 2 of this chapter discusses the HDF5 error handling programming
model. </p>
<p>Section 3 presents summaries of HDF5’s error handling functions.</p>
<p>Section 4 discusses the basic error concepts such as error
stack, error record, and error message and describes the related API
functions.
These concepts and functions are sufficient for application programs to
trace errors inside the HDF5 Library.</p>
<p>Section 5 talks about the advanced concepts of error class and error
stack handle and talks about the related functions. With these concepts
and functions,
an application library or program using the HDF5 Library can have its own
error report blended with HDF5’s error report.</p>
<p>Starting with Release 1.8, we have a new set of Error Handling API functions.
For the purpose of backward compatibility with version 1.6 and before, we
still keep the old API functions, <code>H5Epush</code>, <code>H5Eprint</code>,
<code>H5Ewalk</code>, <code>H5Eclear</code>, <code>H5Eget_auto</code>,
<code>H5Eset_auto</code>. These functions do not have the error stack as
parameter. The library allows them to operate on the default error stack.
Users do not have to change their code to catch up with the new Error API
but are encouraged to do so.</p>
<p>The old API is similar to functionality discussed in Section 4. The
functionality discussed in Section 5, the ability of allowing applications to
add their own error records, is the library new design for the Error API.</p>
<a name="ProgModel">
<h3 class="pagebefore">9.2. Programming Model</h3>
</a>
<p><i>This section is under construction.</i></p>
<!-- NEW PAGE -->
<a name="ErrorHandling">
<h3 class="pagebefore">9.3. Error Handling (H5E) Function Summaries</h3>
</a>
<p>Functions that can be used to handle errors (H5E functions) are listed
below. </p>
<br />
<table width="600" cellspacing="0" align="center" cellpadding="0">
<tr valign="bottom">
<td colspan="3" align="left" valign="bottom">
<b>Function Listing 1. Error handling functions (H5E)
</b></td>
</tr>
<tr><td colspan="3"><hr color="green" size="3" /></td></tr>
<tr valign="top">
<td>
<b>C Function<br />Fortran Function</b>
</td><td> </td>
<td>
<b>Purpose</b>
</td>
</tr>
<tr><td colspan="3"><hr color="green" size="1" /></td></tr>
<tr valign="top">
<td>
<code>H5Eauto_is_v2<br />(none)</code>
</td><td> </td>
<td>
Determines the type of error stack.
</td>
</tr>
<tr><td colspan="3"><hr color="green" size="1" /></td></tr>
<tr valign="top">
<td>
<code>H5Eclear<br />h5eclear_f</code>
</td><td> </td>
<td>
Clears the error stack for the current thread.
The C function is a macro: see <a href="../RM/APICompatMacros.html">
“API Compatibility Macros in HDF5.”</a>
</td>
</tr>
<tr><td colspan="3"><hr color="green" size="1" /></td></tr>
<tr valign="top">
<td>
<code>H5Eclear_stack<br />(none)</code>
</td><td> </td>
<td>
Clears the error stack for the current thread.
</td>
</tr>
<tr><td colspan="3"><hr color="green" size="1" /></td></tr>
<tr valign="top">
<td>
<code>H5Eclose_msg<br />(none)</code>
</td><td> </td>
<td>
Closes an error message identifier.
</td>
</tr>
<tr><td colspan="3"><hr color="green" size="1" /></td></tr>
<tr valign="top">
<td>
<code>H5Eclose_stack<br />(none)</code>
</td><td> </td>
<td>
Closes object handle for error stack.
</td>
</tr>
<tr><td colspan="3"><hr color="green" size="1" /></td></tr>
<tr valign="top">
<td>
<code>H5Ecreate_msg<br />(none)</code>
</td><td> </td>
<td>
Add major error message to an error class.
</td>
</tr>
<tr><td colspan="3"><hr color="green" size="1" /></td></tr>
<tr valign="top">
<td>
<code>H5Eget_auto<br />h5eget_auto_f</code>
</td><td> </td>
<td>
Returns the current settings for the automatic error stack
traversal function and its data.
The C function is a macro: see <a href="../RM/APICompatMacros.html">
“API Compatibility Macros in HDF5.”</a>
</td>
</tr>
<tr><td colspan="3"><hr color="green" size="1" /></td></tr>
<tr valign="top">
<td>
<code>H5Eget_class_name<br />(none)</code>
</td><td> </td>
<td>
Retrieves error class name.
</td>
</tr>
<tr><td colspan="3"><hr color="green" size="1" /></td></tr>
<tr valign="top">
<td>
<code>H5Eget_current_stack<br />(none)</code>
</td><td> </td>
<td>
Registers the current error stack.
</td>
</tr>
<tr><td colspan="3"><hr color="green" size="1" /></td></tr>
<tr valign="top">
<td>
<code>H5Eget_msg<br />(none)</code>
</td><td> </td>
<td>
Retrieves an error message.
</td>
</tr>
<tr><td colspan="3"><hr color="green" size="1" /></td></tr>
<tr valign="top">
<td>
<code>H5Eget_num<br />(none)</code>
</td><td> </td>
<td>
Retrieves the number of error messages in an error stack.
</td>
</tr>
<tr><td colspan="3"><hr color="green" size="1" /></td></tr>
<tr valign="top">
<td>
<code>H5Epop<br />(none)</code>
</td><td> </td>
<td>
Deletes specified number of error messages from the error stack.
</td>
</tr>
<tr><td colspan="3"><hr color="green" size="1" /></td></tr>
<tr valign="top">
<td>
<code>H5Eprint<br />h5eprint_f</code>
</td><td> </td>
<td>
Prints the error stack in a default manner.
The C function is a macro: see <a href="../RM/APICompatMacros.html">
“API Compatibility Macros in HDF5.”</a>
</td>
</tr>
<tr><td colspan="3"><hr color="green" size="1" /></td></tr>
<tr valign="top">
<td>
<code>H5Epush<br />(none)</code>
</td><td> </td>
<td>
Pushes new error record onto error stack.
The C function is a macro: see <a href="../RM/APICompatMacros.html">
“API Compatibility Macros in HDF5.”</a>
</td>
</tr>
<tr><td colspan="3"><hr color="green" size="1" /></td></tr>
<tr valign="top">
<td>
<code>H5Eregister_class<br />(none)</code>
</td><td> </td>
<td>
Registers a client library or application program
to the HDF5 error API.
</td>
</tr>
<tr><td colspan="3"><hr color="green" size="1" /></td></tr>
<tr valign="top">
<td>
<code>H5Eset_auto<br />h5eset_auto_f</code>
</td><td> </td>
<td>
Turns automatic error printing on or off.
The C function is a macro: see <a href="../RM/APICompatMacros.html">
“API Compatibility Macros in HDF5.”</a>
</td>
</tr>
<tr><td colspan="3"><hr color="green" size="1" /></td></tr>
<tr valign="top">
<td>
<code>H5Eset_current_stack<br />(none)</code>
</td><td> </td>
<td>
Replaces the current error stack.
</td>
</tr>
<tr><td colspan="3"><hr color="green" size="1" /></td></tr>
<tr valign="top">
<td>
<code>H5Eunregister_class<br />(none)</code>
</td><td> </td>
<td>
Removes an error class.
</td>
</tr>
<tr><td colspan="3"><hr color="green" size="1" /></td></tr>
<tr valign="top">
<td>
<code>H5Ewalk<br />(none)</code>
</td><td> </td>
<td>
Walks the error stack for the current thread,
calling a specified function.
The C function is a macro: see <a href="../RM/APICompatMacros.html">
“API Compatibility Macros in HDF5.”</a>
</td>
<tr><td colspan="3"><hr color="green" size="3" /></td></tr>
</table>
<br />
<!-- NEW PAGE -->
<a name="BasicErrorHandling">
<h3>9.4. Basic Error Handling Operations</h3>
</a>
<h4>9.4.1. Introduction</h4>
<p>Let us first try to understand the error stack. An <em>error stack</em>
is a collection of error records. Error records can be pushed onto or
popped off the error stack. By default, when an error occurs deep within
the HDF5 Library, an error record is pushed onto an error stack and that
function returns a failure indication. Its caller detects the failure, pushes
another record onto the stack, and returns a failure indication. This
continues until the API function called by the application returns a failure
indication. The next API function being called will reset the error stack.
All HDF5 Library error records belong to the same error class (explained in
Section 5).</p>
<h4>9.4.2. Error Stack and Error Message</h4>
<p>In normal circumstances, an error causes the stack to be printed on the
standard error stream automatically. This automatic error stack is the
library’s default stack. For all the functions in this section,
whenever an error stack ID is needed as a parameter, <code>H5E_DEFAULT</code>
can be used to indicate the library’s default stack. The first
error record of the error stack, number <code>#000</code>, is produced
by the API function itself and is usually sufficient to indicate to
the application what went wrong.</p>
<h4>Example: An Error Report</h4>
<p>If an application calls <code>H5Tclose</code> on a predefined datatype,
then the message in the example below is printed on the standard error
stream.
This is a simple error that has only one component, the API function;
other errors may have many components.</p>
<table width="600" cellspacing="0" align="center">
<tr valign="top">
<td align="left">
<hr color="green" size="3"/>
<pre>
HDF5-DIAG: Error detected in HDF5 (1.6.4) thread 0.
#000: H5T.c line 462 in H5Tclose(): predefined datatype
major: Function argument
minor: Bad value</pre></td>
</tr>
<tr><td><hr color="green" size="1" /></td></tr>
<tr valign="top">
<td align="left">
<b>Example 1. An error report</b>
<hr color="green" size="3"/></td>
</tr>
</table>
<br />
<p>In the example above, we can see that an <em>error record</em> has a major
message and a minor message. A <em>major message</em> generally
indicates where the error happens. The location can be a dataset or
a dataspace, for example. A <em>minor message</em> explains further
details of the error. An example is “unable to open file”.
Another
specific detail about the error can be found at the end of the first
line of each error record. This <em>error description</em> is usually
added by the library designer to tell what exactly goes wrong.
In the example above, the “predefined datatype” is an error
description.</p>
<h4>9.4.3. Print and Clear an Error Stack</h4>
<p>Besides the automatic error report, the error stack can also be printed
and cleared by the functions <code>H5Eprint()</code> and
<code>H5Eclear_stack()</code>. If an application wishes to make explicit
calls to <code>H5Eprint()</code> to print the error stack, the
automatic printing should be turned off to prevent error messages from
being displayed twice (see <code>H5Eset_auto()</code> below). </p>
<!-- NEW PAGE -->
<p><b>To print an error stack</b></p>
<p><code><em>herr_t</em> H5Eprint(<em>hid_t</em>
error_stack, <em>FILE *</em> stream)</code></p>
<p>This function prints the error stack specified by <code>error_stack</code>
on the
specified stream, <code>stream</code>. If the error stack is empty,
a one-line message will be printed. The following is an example of such a
message. This message would be generated if the error was in the HDF5
Library. </p>
<p><code>HDF5-DIAG: Error detected in HDF5 Library
version: 1.5.62 thread 0.</code></p>
<p><b>To clear an error stack</b></p>
<p><code><em>herr_t</em> H5Eclear_stack(<em>hid_t</em>
error_stack)</code></p>
<p>The <code>H5Eclear_stack</code> function shown above clears the error
stack specified by
<code>error_stack</code>. <code>H5E_DEFAULT</code> can be passed in to
clear the current error stack. The current stack is also cleared
whenever an API function is called; there are certain exceptions to this
rule such as <code>H5Eprint()</code>. </p>
<h4>9.4.4. Mute Error Stack</h4>
<p>Sometimes an application calls a function for the sake of its return value,
fully expecting the function to fail; sometimes the application wants to
call <code>H5Eprint()</code> explicitly. In these situations, it
would be misleading if an error message were still automatically printed.
Using the <code>H5Eset_auto()</code> function can control the automatic
printing of error messages.</p>
<p><b>To enable or disable automatic printing of errors</b></p>
<p><code><em>herr_t</em> H5Eset_auto(<em>hid_t</em>
error_stack, <em>H5E_auto_t</em> func,
<em>void</em> *client_data)</code></p>
<p>The H5Eset_auto function can be used to turns on or off the automatic
printing of errors for the error stack
specified by <code>error_stack</code>. When turned on (non-null <code>func</code>
pointer), any API function which returns an error indication will first call
<code>func</code>, passing it <code>client_data</code> as an argument.
When the library is first initialized the auto printing function is set to
<code>H5Eprint()</code> (cast appropriately) and <code>client_data</code> is
the standard error stream pointer, <code>stderr</code>.</p>
<p><b>To see the current settings</b></p>
<p><code><em>herr_t</em> H5Eget_auto(<em>hid_t</em>
error_stack, <em>H5E_auto_t</em> * func,
<em>void</em> **client_data )</code></p>
<p>The function above returns the current settings for the automatic error
stack traversal
function, <code>func</code>, and its data, <code>client_data</code>.
If either or both of the arguments are null, then the value is not
returned.</p>
<!-- NEW PAGE -->
<h4>Example: Error Control</h4>
<p>An application can temporarily turn off error messages while
“probing” a function. See the example below.</p>
<table width="600" cellspacing="0" align="center">
<tr valign="top">
<td align="left">
<hr color="green" size="3"/>
<pre>
/* Save old error handler */
H5E_auto2_t oldfunc;
void *old_client_data;
H5Eget_auto(error_stack, &old_func, &old_client_data);
/* Turn off error handling */
H5Eset_auto(error_stack, NULL, NULL);
/* Probe. Likely to fail, but that’s okay */
status = H5Fopen (......);
/* Restore previous error handler */
H5Eset_auto(error_stack, old_func, old_client_data);</pre></td>
</tr>
<tr><td><hr color="green" size="1" /></td></tr>
<tr valign="top">
<td align="left">
<b>Example 2. Turn off error messages while probing a function</b>
<hr color="green" size="3"/></td>
</tr>
</table>
<br />
<p>Or automatic printing can be disabled altogether and error messages
can be explicitly printed.</p>
<table width="600" cellspacing="0" align="center">
<tr valign="top">
<td align="left">
<hr color="green" size="3"/>
<pre>
/* Turn off error handling permanently */
H5Eset_auto(error_stack, NULL, NULL);
/* If failure, print error message */
if (H5Fopen (....)<0) {
H5Eprint(H5E_DEFAULT, stderr);
exit (1);
}</pre></td>
</tr>
<tr><td><hr color="green" size="1" /></td></tr>
<tr valign="top">
<td align="left">
<b>Example 3. Disable automatic printing and explicitly print
error messages</b>
<hr color="green" size="3"/></td>
</tr>
</table>
<br />
<h4>9.4.5. Customized Printing of an Error Stack</h4>
<p>Applications are allowed to define an automatic error traversal
function other than the default <code>H5Eprint()</code>. For
instance, one can define a function that prints a simple, one-line
error message to the standard error stream and then exits. The first
example below defines a such a function. The second example below installs
the function as the error handler.</p>
<!-- NEW PAGE -->
<table width="600" cellspacing="0" align="center">
<tr valign="top">
<td align="left">
<hr color="green" size="3"/>
<pre>
herr_t
my_hdf5_error_handler(void *unused)
{
fprintf (stderr, “An HDF5 error was detected. Bye.\n”);
exit (1);
}</pre></td>
</tr>
<tr><td><hr color="green" size="1" /></td></tr>
<tr valign="top">
<td align="left">
<b>Example 4. Defining a function to print a simple error message</b>
<hr color="green" size="3"/></td></tr>
</table>
<br />
<br />
<table width="600" cellspacing="0" align="center">
<tr valign="top">
<td align="left">
<hr color="green" size="3"/>
<pre>
H5Eset_auto(H5E_DEFAULT, my_hdf5_error_handler, NULL);</pre></td>
</tr>
<tr><td><hr color="green" size="1" /></td></tr>
<tr valign="top">
<td align="left">
<b>Example 5. The user-defined error handler</b>
<hr color="green" size="3"/></td>
</tr>
</table>
<br />
<h4>9.4.6. Walk through the Error Stack</h4>
<p>The <code>H5Eprint()</code> function is actually just a
wrapper around the more complex <code>H5Ewalk()</code>
function which traverses an error stack and calls a user-defined
function for each member of the stack. The example below shows how
<code>H5Ewalk</code> is used.</p>
<p><code><em>herr_t</em> H5Ewalk(<em>hid_t</em>
err_stack, <em>H5E_direction_t</em>
direction, <em>H5E_walk_t</em> func,
<em>void</em> *client_data)</code></p>
<p>The error stack <code>err_stack</code> is traversed and
<code>func</code> is
called for each member of the stack. Its arguments are an integer
sequence number beginning at zero (regardless of <code>direction</code>)
and the <code>client_data</code> pointer. If <code>direction</code>
is <code>H5E_WALK_UPWARD</code>, then traversal begins at the inner-most
function that detected the error and concludes with the API function.
Use <code>H5E_WALK_DOWNWARD</code> for the opposite order.</p>
<h4>9.4.7. Traverse an Error Stack with a Callback Function</h4>
<p>An error stack traversal callback function takes three arguments:
<code>n</code> is a sequence number beginning at zero for each traversal,
<code>eptr</code> is a pointer to an error stack member, and
<code>client_data</code> is the same pointer used in the example above
passed to <code>H5Ewalk()</code>. See the example below.</p>
<p><code>typedef <em>herr_t</em> (*H5E_walk_t)(<em>unsigned</em>
n, <em>H5E_error2_t</em> *eptr, <em>void</em> *client_data)</code></p>
<p>The <code>H5E_error2_t</code> structure is shown below.</p>
<!-- NEW PAGE -->
<pre>
typedef struct {
hid_t cls_id;
hid_t maj_num;
hid_t min_num;
unsigned line;
const char *func_name;
const char *file_name;
const char *desc;
} H5E_error2_t;
</pre>
<p>The <code>maj_num</code> and <code>min_num</code> are major and minor
error IDs, <code>func_name</code> is the name of the function where the error
was detected, <code>file_name</code> and <code>line</code> locate the
error within the HDF5 Library source code, and <code>desc</code> points
to a description of the error.</p>
<h4>Example: Callback Function</h4>
<p>The following example shows a user-defined callback function.</p>
<table width="600" cellspacing="0" align="center">
<tr valign="top">
<td align="left">
<hr color="green" size="3"/>
<pre>
#define MSG_SIZE 64
herr_t
custom_print_cb(unsigned n, const H5E_error2_t *err_desc, void* client_data)
{
FILE *stream = (FILE *)client_data;
char maj[MSG_SIZE];
char min[MSG_SIZE];
char cls[MSG_SIZE];
const int indent = 4;
/* Get descriptions for the major and minor error numbers */
if(H5Eget_class_name(err_desc->cls_id, cls, MSG_SIZE)<0)
TEST_ERROR;
if(H5Eget_msg(err_desc->maj_num, NULL, maj, MSG_SIZE)<0)
TEST_ERROR;
if(H5Eget_msg(err_desc->min_num, NULL, min, MSG_SIZE)<0)
TEST_ERROR;
fprintf (stream, “%*serror #%03d: %s in %s(): line %u\n”,
indent, “”, n, err_desc->file_name,
err_desc->func_name, err_desc->line);
fprintf (stream, “%*sclass: %s\n”, indent*2, “”, cls);
fprintf (stream, “%*smajor: %s\n”, indent*2, “”, maj);
fprintf (stream, “%*sminor: %s\n”, indent*2, “”, min);
return 0;
error:
return -1;
}</pre></td>
</tr>
<tr><td><hr color="green" size="1" /></td></tr>
<tr valign="top">
<td align="left">
<b>Example 6. A user-defined callback function</b>
<hr color="green" size="3"/></td>
</tr>
</table>
<br />
<p><b>Programming Note for C++ Developers Using C Functions</b> </p>
<p>If a C routine that takes a function pointer as an argument is called
from within C++ code, the C routine should be returned from normally. </p>
<p>Examples of this kind of routine include callbacks such as
<code>H5Pset_elink_cb</code> and <code>H5Pset_type_conv_cb</code>
and functions such as <code>H5Tconvert</code> and <code>H5Ewalk2</code>.</p>
<p>Exiting the routine in its normal fashion allows the HDF5 C Library
to clean up its work properly. In other words, if the C++ application
jumps out of the routine back to the C++ “catch”
statement, the library is not given the opportunity to close any
temporary data structures that were set up when the routine was
called. The C++ application should save some state as the routine is
started so that any problem that occurs might be diagnosed.</p>
<!-- NEW PAGE -->
<a name="AdvancedErrorHandling">
<h3>9.5. Advanced Error Handling Operations</h3>
</a>
<h4>9.5.1. Introduction</h4>
<p>Section 4 discusses the basic error handling operations of the library.
In that section, all the error records on the error stack are from the
library itself. In this section, we are going to introduce the operations
that allow an application program to push its own error records onto the
error stack once it declares an error class of its own through the
HDF5 Error API.</p>
<h4>Example: An Error Report</h4>
<p>An error report shows both the library’s error record and the
application’s error records. See the example below.</p>
<table width="600" cellspacing="0" align="center">
<tr valign="top">
<td align="left">
<hr color="green" size="3"/>
<pre>
Error Test-DIAG: Error detected in Error Program (1.0) thread 8192:
#000: ../../hdf5/test/error_test.c line 468 in main(): Error test failed
major: Error in test
minor: Error in subroutine
#001: ../../hdf5/test/error_test.c line 150 in test_error(): H5Dwrite failed
as supposed to
major: Error in IO
minor: Error in H5Dwrite
HDF5-DIAG: Error detected in HDF5 (1.7.5) thread 8192:
#002: ../../hdf5/src/H5Dio.c line 420 in H5Dwrite(): not a dataset
major: Invalid arguments to routine
minor: Inappropriate type </pre></td>
</tr>
<tr><td><hr color="green" size="1" /></td></tr>
<tr valign="top">
<td align="left">
<b>Example 7. An error report</b>
<hr color="green" size="3"/></td>
</tr>
</table>
<br />
<p>In the line above error record <code>#002</code> in the example above,
the starting phrase is <code>HDF5</code>. This is the error class name
of the HDF5 Library. All of the library’s error messages
(major and minor) are in this default error class.
The <code>Error Test</code> in the beginning of the line above error record
<code>#000</code> is the name of the application’s error class.
The first two error records, <code>#000</code> and <code>#001</code>,
are from application’s error class.</p>
<p>By definition, an error class is a group of major and minor error messages
for a library (the HDF5 Library or an application library built on
top of the
HDF5 Library) or an application program. The error class can be registered
for a
library or program through the HDF5 Error API. Major
and minor messages can be defined in an error class. An application will
have object handles for the error class and for major and minor messages for
further operation. See the example below.</p>
<!-- NEW PAGE -->
<table width="600" cellspacing="0" align="center">
<tr valign="top">
<td align="left">
<hr color="green" size="3"/>
<pre>
#define MSG_SIZE 64
herr_t
custom_print_cb(unsigned n, const H5E_error2_t *err_desc, void* client_data)
{
FILE *stream = (FILE *)client_data;
char maj[MSG_SIZE];
char min[MSG_SIZE];
char cls[MSG_SIZE];
const int indent = 4;
/* Get descriptions for the major and minor error numbers */
if(H5Eget_class_name(err_desc->cls_id, cls, MSG_SIZE)<0)
TEST_ERROR;
if(H5Eget_msg(err_desc->maj_num, NULL, maj, MSG_SIZE)<0)
TEST_ERROR;
if(H5Eget_msg(err_desc->min_num, NULL, min, MSG_SIZE)<0)
TEST_ERROR;
fprintf (stream, “%*serror #%03d: %s in %s(): line %u\n”,
indent, “”, n, err_desc->file_name,
err_desc->func_name, err_desc->line);
fprintf (stream, “%*sclass: %s\n”, indent*2, “”, cls);
fprintf (stream, “%*smajor: %s\n”, indent*2, “”, maj);
fprintf (stream, “%*sminor: %s\n”, indent*2, “”, min);
return 0;
error:
return -1;
}</pre></td>
</tr>
<tr><td><hr color="green" size="1" /></td></tr>
<tr valign="top">
<td align="left">
<b>Example 8. Defining an error class</b>
<hr color="green" size="3"/></td>
</tr>
</table>
<br />
<h4>9.5.2. More Error API Functions</h4>
<p>The Error API has functions that can be used to register or unregister
an error class,
to create or close error messages, and to query an error class or
error message. These functions are illustrated below.</p>
<p><b>To register an error class</b></p>
<code><em>hid_t</em> H5Eregister_class(<em>const char*</em>
cls_name, <em>const char*</em> lib_name,
<em>const char*</em> version)</code>
<p>This function registers an error class with the HDF5 Library so that the
application
library or program can report errors together with the HDF5 Library.</p>
<p><b>To add an error message to an error class</b></p>
<p><code><em>hid_t</em> H5Ecreate_msg(<em>hid_t</em> class,
<em>H5E_type_t</em> msg_type, <em>const char*</em> mesg)</code></p>
<p>This function adds an error message to an error class defined by an
application library or program. The error message can be either major
or minor which is indicated by parameter <code>msg_type</code>.</p>
<p><b>To get the name of an error class</b></p>
<p><code><em>ssize_t</em> H5Eget_class_name(<em>hid_t</em> class_id,
<em>char*</em> name, <em>size_t</em> size)</code></p>
<p>This function retrieves the name of the error class specified by
the class <code>ID</code>.</p>
<p><b>To retrieve an error message</b></p>
<p><code><em>ssize_t</em> H5Eget_msg(<em>hid_t</em> mesg_id,
<em>H5E_type_t*</em> mesg_type, <em>char*</em> mesg,
<em>size_t</em> size)</code></p>
<p>This function retrieves the error message including its length and
type.</p>
<p><b>To close an error message</b></p>
<p><code><em>herr_t</em> H5Eclose_msg(<em>hid_t</em>
mesg_id)</code></p>
<p>This function closes an error message.</p>
<p><b>To remove an error class</b></p>
<p><code><em>herr_t</em> H5Eunregister_class(<em>hid_t</em>
class_id)</code></p>
<p>This function removes an error class from the Error API.</p>
<br />
<h4>Example: Error Class and its Message</h4>
<p>The example below shows how an application creates an error class and
error messages.</p>
<table width="600" cellspacing="0" align="center">
<tr valign="top">
<td align="left">
<hr color="green" size="3"/>
<pre>
/* Create an error class */
class_id = H5Eregister_class(ERR_CLS_NAME, PROG_NAME, PROG_VERS);
/* Retrieve class name */
H5Eget_class_name(class_id, cls_name, cls_size);
/* Create a major error message in the class */
maj_id = H5Ecreate_msg(class_id, H5E_MAJOR, “... ...”);
/* Create a minor error message in the class */
min_id = H5Ecreate_msg(class_id, H5E_MINOR, “... ...”);</pre></td>
</tr>
<tr><td><hr color="green" size="1" /></td></tr>
<tr valign="top">
<td align="left">
<b>Example 9. Create an error class and error messages</b>
<hr color="green" size="3"/></td>
</tr>
</table>
<br />
<p>The example below shows how an application closes error messages and
unregisters the error class.</p>
<table width="600" cellspacing="0" align="center">
<tr valign="top">
<td align="left">
<hr color="green" size="3"/>
<pre>
H5Eclose_msg(maj_id);
H5Eclose_msg(min_id);
H5Eunregister_class(class_id);</pre></td>
</tr>
<tr><td><hr color="green" size="1" /></td></tr>
<tr valign="top">
<td align="left">
<b>Example 10. Closing error messages and unregistering the error
class</b>
<hr color="green" size="3"/></td>
</tr>
</table>
<br />
<h4>9.5.3. Pushing an Application Error Message onto Error Stack</h4>
<p>An application can push error records onto or pop error records
off of the error stack just as the library does internally. An
error stack can be registered, and an object handle can be
returned to the application so that the application can
manipulate a registered error stack.</p>
<p><b>To register the current stack</b></p>
<p><code><em>hid_t</em> H5Eget_current_stack(void)</code></p>
<p>This function registers the current error stack, returns an object
handle, and clears the current error stack. An empty error stack will
also be assigned an ID.</p>
<p><b>To replace the current error stack with another</b></p>
<p><code><em>herr_t</em> H5Eset_current_stack(<em>hid_t</em>
error_stack)</code></p>
<p>This function replaces the current error stack with another error stack
specified by <code>error_stack</code> and clears the current error stack.
The object handle <code>error_stack</code> is closed after this function
call.</p>
<p><b>To push a new error record to the error stack</b></p>
<p><code><em>herr_t</em> H5Epush(<em>hid_t</em>
error_stack, <em>const char*</em> file,
<em>const char*</em> func, <em>unsigned</em> line,
<em>hid_t</em> cls_id, <em>hid_t</em> major_id,
<em>hid_t</em> minor_id, <em>const char*</em> desc,
... )</code></p>
<p>This function pushes a new error record onto the error stack for the
current thread.</p>
<p><b>To delete some error messages</b></p>
<p><code><em>herr_t</em> H5Epop(<em>hid_t</em> error_stack,
<em>size_t</em> count)</code></p>
<p>This function deletes some error messages from the error stack.</p>
<p><b>To retrieve the number of error records</b></p>
<p><code>int H5Eget_num(<em>hid_t</em> error_stack)</code>
<p>This function retrieves the number of error records from an error
stack.</p>
<!-- NEW PAGE -->
<p><b>To clear the error stack</b></p>
<p><code><em>herr_t</em> H5Eclear_stack(<em>hid_t</em>
error_stack)</code></p>
<p>This function clears the error stack.</p>
<p><b>To close the object handle for an error stack</b></p>
<p><code><em>herr_t</em> H5Eclose_stack(<em>hid_t</em>
error_stack</code>)</p>
<p>This function closes the object handle for an error stack and
releases its resources.</p>
<br />
<h4>Example: Working with an Error Stack</h4>
<p>The example below shows how an application pushes an error record onto
the default error stack.</p>
<table width="600" cellspacing="0" align="center">
<tr valign="top">
<td align="left">
<hr color="green" size="3"/>
<pre>
/* Make call to HDF5 I/O routine */
if((dset_id=H5Dopen(file_id, dset_name, access_plist))<0)
{
/* Push client error onto error stack */
H5Epush(H5E_DEFAULT,__FILE__,FUNC,__LINE__,cls_id,CLIENT_ERR_MAJ_IO,
CLIENT_ERR_MINOR_OPEN,“H5Dopen failed”);
/* Indicate error occurred in function */
return(0);
}</pre></td>
</tr>
<tr><td><hr color="green" size="1" /></td></tr>
<tr valign="top">
<td align="left">
<b>Example 11. Pushing an error message to an error stack</b>
<hr color="green" size="3"/></td>
</tr>
</table>
<br />
<p>The example below shows how an application registers the current error
stack and creates an object handle to avoid another HDF5 function
from clearing the error stack.</p>
<!-- NEW PAGE -->
<table width="600" cellspacing="0" align="center">
<tr valign="top">
<td align="left">
<hr color="green" size="3"/>
<pre>
if(H5Dwrite(dset_id, mem_type_id, mem_space_id, file_space_id,
dset_xfer_plist_id, buf)<0)
{
/* Push client error onto error stack */
H5Epush(H5E_DEFAULT,__FILE__,FUNC,__LINE__,cls_id,CLIENT_ERR_MAJ_IO,
CLIENT_ERR_MINOR_HDF5,“H5Dwrite failed”);
/* Preserve the error stack by assigning an object handle to it */
error_stack = H5Eget_current_stack();
/* Close dataset */
H5Dclose(dset_id);
/* Replace the current error stack with the preserved one */
H5Eset_current_stack(error_stack);
Return(0);
}</pre></td>
</tr>
<tr><td><hr color="green" size="1" /></td></tr>
<tr valign="top">
<td align="left">
<b>Example 12. Registering the error stack</b>
<hr color="green" size="3"/></td></tr>
</table>
<br />
<br />
<br />
<!-- HEADER RIGHT " " -->
</body>
</html>
|
