205 lines
8.7 KiB
Plaintext
205 lines
8.7 KiB
Plaintext
How to write code for CVS
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* Compiler options
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If you are using GCC, you'll want to configure with -Wall, which can
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detect many programming errors. This is not the default because it
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might cause spurious warnings, but at least on some machines, there
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should be no spurious warnings. For example:
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$ CFLAGS="-g -Wall" ./configure
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Configure is not very good at remembering this setting; it will get
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wiped out whenever you do a ./config.status --recheck, so you'll need
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to use:
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$ CFLAGS="-g -Wall" ./config.status --recheck
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* Indentation style
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CVS mostly uses a consistent indentation style which looks like this:
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void
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foo (arg)
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char *arg;
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{
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if (arg != NULL)
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{
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bar (arg);
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baz (arg);
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}
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switch (c)
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{
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case 'A':
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aflag = 1;
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break;
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}
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}
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The file cvs-format.el contains settings for emacs and the NEWS file
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contains a set of options for the indent program which I haven't tried
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but which are correct as far as I know. You will find some code which
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does not conform to this indentation style; the plan is to reindent it
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as those sections of the code are changed (one function at a time,
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perhaps).
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In a submitted patch it is acceptable to refrain from changing the
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indentation of large blocks of code to minimize the size of the patch;
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the person checking in such a patch should reindent it.
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* Portability
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The general rule for portability is that it is only worth including
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portability cruft for systems on which people are actually testing and
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using new CVS releases. Without testing, CVS will fail to be portable
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for any number of unanticipated reasons.
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The current consequence of that general rule seems to be that if it
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is in ANSI C and it is in SunOS4 (using /bin/cc), generally it is OK
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to use it without ifdefs (for example, assert() and void * as long as
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you add more casts to and from void * than ANSI requires. But not
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function prototypes). Such constructs are generally portable enough,
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including to NT, OS/2, VMS, etc.
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* Run-time behaviors
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Use assert() to check "can't happen" conditions internal to CVS. We
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realize that there are functions in CVS which instead return NULL or
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some such value (thus confusing the meaning of such a returned value),
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but we want to fix that code. Of course, bad input data, a corrupt
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repository, bad options, etc., should always print a real error
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message instead.
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Do not use arbitrary limits (such as PATH_MAX) except perhaps when the
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operating system or some external interface requires it. We spent a
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lot of time getting rid of them, and we don't want to put them back.
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If you find any that we missed, please report it as with other bugs.
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In most cases such code will create security holes (for example, for
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anonymous readonly access via the CVS protocol, or if a WWW cgi script
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passes client-supplied arguments to CVS).
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Although this is a long-term goal, it also would be nice to move CVS
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in the direction of reentrancy. This reduces the size of the data
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segment and will allow a multi-threaded server if that is desirable.
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It is also useful to write the code so that it can be easily be made
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reentrant later. For example, if you need to pass data from a
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Parse_Info caller to its callproc, you need a static variable. But
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use a single pointer so that when Parse_Info is fixed to pass along a
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void * argument, then the code can easily use that argument.
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* Coding standards in general
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Generally speaking the GNU coding standards are mostly used by CVS
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(but see the exceptions mentioned above, such as indentation style,
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and perhaps an exception or two we haven't mentioned). This is the
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file standards.text at the GNU FTP sites.
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Filenames for .c and .h files may contain _ but should not contain -
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(the latter causes Visual C++ 2.1 to create makefiles which Visual C++
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4.0 cannot use).
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* Writing patches (strategy)
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Only some kinds of changes are suitable for inclusion in the
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"official" CVS. Bugfixes, where CVS's behavior contradicts the
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documentation and/or expectations that everyone agrees on, should be
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OK (strategically). For features, the desirable attributes are that
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the need is clear and that they fit nicely into the architecture of
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CVS. Is it worth the cost (in terms of complexity or any other
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tradeoffs involved)? Are there better solutions?
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If the design is not yet clear (which is true of most features), then
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the design is likely to benefit from more work and community input.
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Make a list of issues, or write documentation including rationales for
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how one would use the feature. Discuss it with coworkers, a
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newsgroup, or a mailing list, and see what other people think.
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Distribute some experimental patches and see what people think. The
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intention is arrive at some kind of rough community consensus before
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changing the "official" CVS. Features like zlib, encryption, and
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the RCS library have benefitted from this process in the past.
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If longstanding CVS behavior, that people may be relying on, is
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clearly deficient, it can be changed, but only slowly and carefully.
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For example, the global -q option was introduced in CVS 1.3 but the
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command -q options, which the global -q replaced, were not removed
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until CVS 1.6.
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* Writing patches (tactics)
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When you first distribute a patch it may be suitable to just put forth
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a rough patch, or even just an idea. But before the end of the
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process the following should exist:
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- ChangeLog entry (see the GNU coding standards for details).
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- Changes to the NEWS file and cvs.texinfo, if the change is a
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user-visible change worth mentioning.
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- Somewhere, a description of what the patch fixes (often in
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comments in the code, or maybe the ChangeLog or documentation).
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- Most of the time, a test case (see TESTS). It can be quite
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frustrating to fix a bug only to see it reappear later, and adding
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the case to the testsuite, where feasible, solves this and other
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problems.
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If you solve several unrelated problems, it is generally easier to
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consider the desirability of the changes if there is a separate patch
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for each issue. Use context diffs or unidiffs for patches.
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Include words like "I grant permission to distribute this patch under
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the terms of the GNU Public License" with your patch. By sending a
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patch to bug-cvs@gnu.org, you implicitly grant this permission.
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Submitting a patch to bug-cvs is the way to reach the people who have
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signed up to receive such submissions (including CVS developers), but
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there may or may not be much (or any) response. If you want to pursue
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the matter further, you are probably best off working with the larger
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CVS community. Distribute your patch as widely as desired (mailing
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lists, newsgroups, web sites, whatever). Write a web page or other
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information describing what the patch is for. It is neither practical
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nor desirable for all/most contributions to be distributed through the
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"official" (whatever that means) mechanisms of CVS releases and CVS
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developers. Now, the "official" mechanisms do try to incorporate
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those patches which seem most suitable for widespread usage, together
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with test cases and documentation. So if a patch becomes sufficiently
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popular in the CVS community, it is likely that one of the CVS
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developers will eventually try to do something with it. But dealing
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with the CVS developers may be the last step of the process rather
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than the first.
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* What is the schedule for the next release?
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There isn't one. That is, upcoming releases are not announced (or
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even hinted at, really) until the feature freeze which is
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approximately 2 weeks before the final release (at this time test
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releases start appearing and are announced on info-cvs). This is
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intentional, to avoid a last minute rush to get new features in.
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* Mailing lists
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Anyone can add themselves to the following mailing lists:
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devel-cvs. Unless you are accepted as a CVS developer as
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described in the DEVEL-CVS file, you will only be able to
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read this list, not send to it. The charter of the list is
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also in DEVEL-CVS.
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commit-cvs. The only messages sent to this list are sent
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automatically, via the CVS `loginfo' mechanism, when someone
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checks something in to the master CVS repository.
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test-results. The only messages sent to this list are sent
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automatically, daily, by a script which runs "make check"
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and "make remotecheck" on the master CVS sources.
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To subscribe to devel-cvs, commit-cvs, or test-results, send
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a message to "majordomo@cyclic.com" whose body consists of
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"subscribe <list>", where <list> is devel-cvs, commit-cvs or
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test-results.
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One other list related to CVS development is bug-cvs. This is the
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list which users are requested to send bug reports to. Anyone can
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subscribe; to do so send mail to bug-cvs-request@gnu.org.
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Other CVS discussions take place on the info-cvs mailing list
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(send mail to info-cvs-request@gnu.org to subscribe) or on
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the newsgroup comp.software.config-mgmt.
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