File: c63.htm

package info (click to toggle)
fastdep 0.16-7
  • links: PTS
  • area: main
  • in suites: sarge
  • size: 596 kB
  • ctags: 323
  • sloc: cpp: 2,144; ansic: 814; sh: 208; makefile: 124
file content (262 lines) | stat: -rw-r--r-- 4,684 bytes parent folder | download | duplicates (5)
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
<HTML
><HEAD
><TITLE
>Automatically regenerating dependency information</TITLE
><META
NAME="GENERATOR"
CONTENT="Modular DocBook HTML Stylesheet Version 1.74b"><LINK
REL="HOME"
TITLE="fastdep manual"
HREF="book1.htm"><LINK
REL="PREVIOUS"
TITLE="Writing a make-rule to generate dependency information"
HREF="c49.htm"><LINK
REL="NEXT"
TITLE="Adding an external dependency"
HREF="c90.htm"></HEAD
><BODY
CLASS="CHAPTER"
BGCOLOR="#FFFFFF"
TEXT="#000000"
LINK="#0000FF"
VLINK="#840084"
ALINK="#0000FF"
><DIV
CLASS="NAVHEADER"
><TABLE
SUMMARY="Header navigation table"
WIDTH="100%"
BORDER="0"
CELLPADDING="0"
CELLSPACING="0"
><TR
><TH
COLSPAN="3"
ALIGN="center"
>fastdep manual</TH
></TR
><TR
><TD
WIDTH="10%"
ALIGN="left"
VALIGN="bottom"
><A
HREF="c49.htm"
ACCESSKEY="P"
>Prev</A
></TD
><TD
WIDTH="80%"
ALIGN="center"
VALIGN="bottom"
></TD
><TD
WIDTH="10%"
ALIGN="right"
VALIGN="bottom"
><A
HREF="c90.htm"
ACCESSKEY="N"
>Next</A
></TD
></TR
></TABLE
><HR
ALIGN="LEFT"
WIDTH="100%"></DIV
><DIV
CLASS="CHAPTER"
><H1
><A
NAME="AEN63"
>Chapter 4. Automatically regenerating dependency information</A
></H1
><P
>Every time you change a dependency relationship (for example when
you include an extra header in some source file), you have to regenerate
the dependency information manually by executing
<B
CLASS="COMMAND"
>make .depend</B
>
(as mentioned in the previous chapter deleting <TT
CLASS="FILENAME"
>.depend</TT
>
also works)</P
><P
>Off course this is very error-prone. Why don't we let make regenerate
	the dependencies everytime one of the source files changes? Easy
	enough :</P
><DIV
CLASS="EXAMPLE"
><A
NAME="AEN69"
></A
><P
><B
>Example 4-1. Makefile fragment to generate dependencies each time a source
		file changes (wrong).</B
></P
><PRE
CLASS="PROGRAMLISTING"
>.depend: $(SOURCES)
	fastdep $(SOURCES) &#62; .depend

-include .depend</PRE
></DIV
><P
>This seems to work fine, but in fact doesn't. Suppose
	one (or more) of our source files in <TT
CLASS="VARNAME"
>SOURCES</TT
>
	includes a certain header <TT
CLASS="FILENAME"
>foo.h</TT
>. Now imagine
	that during an edit-compile cycle we don't change
	anything in the source files, but we added a new include
	of <TT
CLASS="FILENAME"
>bar.h</TT
> in <TT
CLASS="FILENAME"
>foo.h</TT
>.
	This means that the dependencies for each source file that
	includes <TT
CLASS="FILENAME"
>foo.h</TT
> must change. However since
	none of the source files themself change, make will find
	that <TT
CLASS="FILENAME"
>.depend</TT
> is still up to date
	and not regenerate it.
	The end result is incorrect dependency information.</P
><P
>To summarize, the dependency information of a source file
	not only depends on the source file itself, but also on all
	files it includes. Hence the earlier makefile fragment is
	incorrect.</P
><P
>To solve this problem, the info manual of GNU make proposes
	a solution where the output of the dependency generator is
	modified by piping it through sed. While this works for
	normal dependency generators like the GNU C/C++ compiler
	(and still works with fastdep), there is a much more elegant
	solution in <SPAN
CLASS="APPLICATION"
>fastdep</SPAN
>.
	By adding the <B
CLASS="COMMAND"
>--remakedeptarget=file</B
>
	command line option fastdep will also emit a suitable
	dependency line for its own output.</P
><DIV
CLASS="EXAMPLE"
><A
NAME="AEN83"
></A
><P
><B
>Example 4-2. Makefile fragment to generate dependencies each time a source
		or included file changes (right).</B
></P
><PRE
CLASS="PROGRAMLISTING"
>.depend:
	fastdep --remakedeptarget=.depend $(ALLSOURCES) &#62; .depend

-include dependinfo</PRE
></DIV
><P
>The <TT
CLASS="FILENAME"
>.depend</TT
> file will now look like this : </P
><PRE
CLASS="SCREEN"
>file1.o: file1.cc \
	header1.h \
	header2.h \
	header3.h
file2.o: file2.cc \
	header1.h \
	header3.h \
	header4.h \
.depend: \
	file1.cc \
	header1.h \
	header2.h \
	header3.h \
	file2.cc \
	header4.h \</PRE
><P
>which is exactly how we want it to be.</P
></DIV
><DIV
CLASS="NAVFOOTER"
><HR
ALIGN="LEFT"
WIDTH="100%"><TABLE
SUMMARY="Footer navigation table"
WIDTH="100%"
BORDER="0"
CELLPADDING="0"
CELLSPACING="0"
><TR
><TD
WIDTH="33%"
ALIGN="left"
VALIGN="top"
><A
HREF="c49.htm"
ACCESSKEY="P"
>Prev</A
></TD
><TD
WIDTH="34%"
ALIGN="center"
VALIGN="top"
><A
HREF="book1.htm"
ACCESSKEY="H"
>Home</A
></TD
><TD
WIDTH="33%"
ALIGN="right"
VALIGN="top"
><A
HREF="c90.htm"
ACCESSKEY="N"
>Next</A
></TD
></TR
><TR
><TD
WIDTH="33%"
ALIGN="left"
VALIGN="top"
>Writing a make-rule to generate dependency information</TD
><TD
WIDTH="34%"
ALIGN="center"
VALIGN="top"
>&nbsp;</TD
><TD
WIDTH="33%"
ALIGN="right"
VALIGN="top"
>Adding an external dependency</TD
></TR
></TABLE
></DIV
></BODY
></HTML
>