1 How to write code for CVS
5 Patches against the development version of CVS are most likely to be accepted:
7 $ cvs -d:pserver:anoncvs@cvs.cvshome.org/cvsroot co ccvs
11 If you are using GCC, you'll want to configure with -Wall, which can
12 detect many programming errors. This is not the default because it
13 might cause spurious warnings, but at least on some machines, there
14 should be no spurious warnings. For example:
16 $ CFLAGS="-g -Wall" ./configure
18 Configure is not very good at remembering this setting; it will get
19 wiped out whenever you do a ./config.status --recheck, so you'll need
22 $ CFLAGS="-g -Wall" ./config.status --recheck
26 CVS mostly uses a consistent indentation style which looks like this:
45 The file cvs-format.el contains settings for emacs and the NEWS file
46 contains a set of options for the indent program which I haven't tried
47 but which are correct as far as I know. You will find some code which
48 does not conform to this indentation style; the plan is to reindent it
49 as those sections of the code are changed (one function at a time,
52 In a submitted patch it is acceptable to refrain from changing the
53 indentation of large blocks of code to minimize the size of the patch;
54 the person checking in such a patch should reindent it.
58 The general rule for portability is that it is only worth including
59 portability cruft for systems on which people are actually testing and
60 using new CVS releases. Without testing, CVS will fail to be portable
61 for any number of unanticipated reasons.
63 The current consequence of that general rule seems to be that if it
64 is in ANSI C and it is in SunOS4 (using /bin/cc), generally it is OK
65 to use it without ifdefs (for example, assert() and void * as long as
66 you add more casts to and from void * than ANSI requires. But not
67 function prototypes). Such constructs are generally portable enough,
68 including to NT, OS/2, VMS, etc.
72 Use assert() to check "can't happen" conditions internal to CVS. We
73 realize that there are functions in CVS which instead return NULL or
74 some such value (thus confusing the meaning of such a returned value),
75 but we want to fix that code. Of course, bad input data, a corrupt
76 repository, bad options, etc., should always print a real error
79 Do not use arbitrary limits (such as PATH_MAX) except perhaps when the
80 operating system or some external interface requires it. We spent a
81 lot of time getting rid of them, and we don't want to put them back.
82 If you find any that we missed, please report it as with other bugs.
83 In most cases such code will create security holes (for example, for
84 anonymous readonly access via the CVS protocol, or if a WWW cgi script
85 passes client-supplied arguments to CVS).
87 Although this is a long-term goal, it also would be nice to move CVS
88 in the direction of reentrancy. This reduces the size of the data
89 segment and will allow a multi-threaded server if that is desirable.
90 It is also useful to write the code so that it can be easily be made
91 reentrant later. For example, if you need to pass data from a
92 Parse_Info caller to its callproc, you need a static variable. But
93 use a single pointer so that when Parse_Info is fixed to pass along a
94 void * argument, then the code can easily use that argument.
96 * Coding standards in general
98 Generally speaking the GNU coding standards are mostly used by CVS
99 (but see the exceptions mentioned above, such as indentation style,
100 and perhaps an exception or two we haven't mentioned). This is the
101 file standards.text at the GNU FTP sites.
103 Filenames for .c and .h files may contain _ but should not contain -
104 (the latter causes Visual C++ 2.1 to create makefiles which Visual C++
107 * Regenerating Build Files
109 On UNIX, if you wish to change the Build files, you will need Autoconf and
112 Some combinations of Automake and Autoconf versions may break the
113 CVS build if file timestamps aren't set correctly and people don't
114 have the same versions the developers do, so the rules to run them
115 automatically aren't included in the generated Makefiles unless you run
116 configure with the --enable-maintainer-mode option.
118 The CVS Makefiles and configure script were built using Automake 1.7.9 and
119 Autoconf 2.58, respectively.
121 There is a known bug in Autoconf 2.57 that will prevent the configure
122 scripts it generates from working on some platforms. Other combinations of
123 autotool versions may or may not work. If you get other versions to work,
124 please send a report to <bug-cvs@gnu.org>.
126 * Writing patches (strategy)
128 Only some kinds of changes are suitable for inclusion in the
129 "official" CVS. Bugfixes, where CVS's behavior contradicts the
130 documentation and/or expectations that everyone agrees on, should be
131 OK (strategically). For features, the desirable attributes are that
132 the need is clear and that they fit nicely into the architecture of
133 CVS. Is it worth the cost (in terms of complexity or any other
134 tradeoffs involved)? Are there better solutions?
136 If the design is not yet clear (which is true of most features), then
137 the design is likely to benefit from more work and community input.
138 Make a list of issues, or write documentation including rationales for
139 how one would use the feature. Discuss it with coworkers, a
140 newsgroup, or a mailing list, and see what other people think.
141 Distribute some experimental patches and see what people think. The
142 intention is arrive at some kind of rough community consensus before
143 changing the "official" CVS. Features like zlib, encryption, and
144 the RCS library have benefitted from this process in the past.
146 If longstanding CVS behavior, that people may be relying on, is
147 clearly deficient, it can be changed, but only slowly and carefully.
148 For example, the global -q option was introduced in CVS 1.3 but the
149 command -q options, which the global -q replaced, were not removed
152 * Writing patches (tactics)
154 When you first distribute a patch it may be suitable to just put forth
155 a rough patch, or even just an idea. But before the end of the
156 process the following should exist:
158 - ChangeLog entry (see the GNU coding standards for details).
160 - Changes to the NEWS file and cvs.texinfo, if the change is a
161 user-visible change worth mentioning.
163 - Somewhere, a description of what the patch fixes (often in
164 comments in the code, or maybe the ChangeLog or documentation).
166 - Most of the time, a test case (see TESTS). It can be quite
167 frustrating to fix a bug only to see it reappear later, and adding
168 the case to the testsuite, where feasible, solves this and other
169 problems. See the TESTS file for notes on writing new tests.
171 If you solve several unrelated problems, it is generally easier to
172 consider the desirability of the changes if there is a separate patch
173 for each issue. Use context diffs or unidiffs for patches.
175 Include words like "I grant permission to distribute this patch under
176 the terms of the GNU Public License" with your patch. By sending a
177 patch to bug-cvs@gnu.org, you implicitly grant this permission.
179 Submitting a patch to bug-cvs is the way to reach the people who have
180 signed up to receive such submissions (including CVS developers), but
181 there may or may not be much (or any) response. If you want to pursue
182 the matter further, you are probably best off working with the larger
183 CVS community. Distribute your patch as widely as desired (mailing
184 lists, newsgroups, web sites, whatever). Write a web page or other
185 information describing what the patch is for. It is neither practical
186 nor desirable for all/most contributions to be distributed through the
187 "official" (whatever that means) mechanisms of CVS releases and CVS
188 developers. Now, the "official" mechanisms do try to incorporate
189 those patches which seem most suitable for widespread usage, together
190 with test cases and documentation. So if a patch becomes sufficiently
191 popular in the CVS community, it is likely that one of the CVS
192 developers will eventually try to do something with it. But dealing
193 with the CVS developers may be the last step of the process rather
196 * What is the schedule for the next release?
198 There isn't one. That is, upcoming releases are not announced (or
199 even hinted at, really) until the feature freeze which is
200 approximately 2 weeks before the final release (at this time test
201 releases start appearing and are announced on info-cvs). This is
202 intentional, to avoid a last minute rush to get new features in.
206 Anyone can add themselves to the following mailing lists:
208 dev. Unless you are accepted as a CVS developer as
209 described in the DEVEL-CVS file, you will only be able to
210 read this list, not send to it. The charter of the list is
212 cvs. The only messages sent to this list are sent
213 automatically, via the CVS `loginfo' mechanism, when someone
214 checks something in to the master CVS repository.
215 test-results. The only messages sent to this list are sent
216 automatically, daily, by a script which runs "make check"
217 and "make remotecheck" on the master CVS sources.
218 To subscribe to dev, cvs, or test-results, send
219 a message to "<list>-subscribe@ccvs.cvshome.org" or visit
220 http://ccvs.cvshome.org/servlets/ProjectMailingListList and follow the
223 One other list related to CVS development is bug-cvs. This is the
224 list which users are requested to send bug reports to. Anyone can
225 subscribe; to do so send mail to bug-cvs-request@gnu.org.
227 Other CVS discussions take place on the info-cvs mailing list
228 (send mail to info-cvs-request@gnu.org to subscribe) or on
229 the newsgroup comp.software.config-mgmt.