HACKING
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上传日期:2007-06-06
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- How to write code for CVS
- * Source
- Patches against the development version of CVS are most likely to be accepted:
- $ cvs -d:pserver:anoncvs@cvs.cvshome.org/cvsroot co ccvs
- * Compiler options
- If you are using GCC, you'll want to configure with -Wall, which can
- detect many programming errors. This is not the default because it
- might cause spurious warnings, but at least on some machines, there
- should be no spurious warnings. For example:
- $ CFLAGS="-g -Wall" ./configure
- Configure is not very good at remembering this setting; it will get
- wiped out whenever you do a ./config.status --recheck, so you'll need
- to use:
- $ CFLAGS="-g -Wall" ./config.status --recheck
- * Indentation style
- CVS mostly uses a consistent indentation style which looks like this:
- void
- foo (arg)
- char *arg;
- {
- if (arg != NULL)
- {
- bar (arg);
- baz (arg);
- }
- switch (c)
- {
- case 'A':
- aflag = 1;
- break;
- }
- }
- The file cvs-format.el contains settings for emacs and the NEWS file
- contains a set of options for the indent program which I haven't tried
- but which are correct as far as I know. You will find some code which
- does not conform to this indentation style; the plan is to reindent it
- as those sections of the code are changed (one function at a time,
- perhaps).
- In a submitted patch it is acceptable to refrain from changing the
- indentation of large blocks of code to minimize the size of the patch;
- the person checking in such a patch should reindent it.
- * Portability
- The general rule for portability is that it is only worth including
- portability cruft for systems on which people are actually testing and
- using new CVS releases. Without testing, CVS will fail to be portable
- for any number of unanticipated reasons.
- The current consequence of that general rule seems to be that if it
- is in ANSI C and it is in SunOS4 (using /bin/cc), generally it is OK
- to use it without ifdefs (for example, assert() and void * as long as
- you add more casts to and from void * than ANSI requires. But not
- function prototypes). Such constructs are generally portable enough,
- including to NT, OS/2, VMS, etc.
- * Run-time behaviors
- Use assert() to check "can't happen" conditions internal to CVS. We
- realize that there are functions in CVS which instead return NULL or
- some such value (thus confusing the meaning of such a returned value),
- but we want to fix that code. Of course, bad input data, a corrupt
- repository, bad options, etc., should always print a real error
- message instead.
- Do not use arbitrary limits (such as PATH_MAX) except perhaps when the
- operating system or some external interface requires it. We spent a
- lot of time getting rid of them, and we don't want to put them back.
- If you find any that we missed, please report it as with other bugs.
- In most cases such code will create security holes (for example, for
- anonymous readonly access via the CVS protocol, or if a WWW cgi script
- passes client-supplied arguments to CVS).
- Although this is a long-term goal, it also would be nice to move CVS
- in the direction of reentrancy. This reduces the size of the data
- segment and will allow a multi-threaded server if that is desirable.
- It is also useful to write the code so that it can be easily be made
- reentrant later. For example, if you need to pass data from a
- Parse_Info caller to its callproc, you need a static variable. But
- use a single pointer so that when Parse_Info is fixed to pass along a
- void * argument, then the code can easily use that argument.
- * Coding standards in general
- Generally speaking the GNU coding standards are mostly used by CVS
- (but see the exceptions mentioned above, such as indentation style,
- and perhaps an exception or two we haven't mentioned). This is the
- file standards.text at the GNU FTP sites.
- Filenames for .c and .h files may contain _ but should not contain -
- (the latter causes Visual C++ 2.1 to create makefiles which Visual C++
- 4.0 cannot use).
- * Regenerating Build Files
- On UNIX, if you wish to change the Build files, you will need Autoconf and
- Automake.
- Some combinations of Automake and Autoconf versions may break the
- CVS build if file timestamps aren't set correctly and people don't
- have the same versions the developers do, so the rules to run them
- automatically aren't included in the generated Makefiles unless you run
- configure with the --enable-maintainer-mode option.
- The CVS Makefiles and configure script were built using Automake 1.7.9 and
- Autoconf 2.58, respectively.
- There is a known bug in Autoconf 2.57 that will prevent the configure
- scripts it generates from working on some platforms. Other combinations of
- autotool versions may or may not work. If you get other versions to work,
- please send a report to <bug-cvs@gnu.org>.
- * Writing patches (strategy)
- Only some kinds of changes are suitable for inclusion in the
- "official" CVS. Bugfixes, where CVS's behavior contradicts the
- documentation and/or expectations that everyone agrees on, should be
- OK (strategically). For features, the desirable attributes are that
- the need is clear and that they fit nicely into the architecture of
- CVS. Is it worth the cost (in terms of complexity or any other
- tradeoffs involved)? Are there better solutions?
- If the design is not yet clear (which is true of most features), then
- the design is likely to benefit from more work and community input.
- Make a list of issues, or write documentation including rationales for
- how one would use the feature. Discuss it with coworkers, a
- newsgroup, or a mailing list, and see what other people think.
- Distribute some experimental patches and see what people think. The
- intention is arrive at some kind of rough community consensus before
- changing the "official" CVS. Features like zlib, encryption, and
- the RCS library have benefitted from this process in the past.
- If longstanding CVS behavior, that people may be relying on, is
- clearly deficient, it can be changed, but only slowly and carefully.
- For example, the global -q option was introduced in CVS 1.3 but the
- command -q options, which the global -q replaced, were not removed
- until CVS 1.6.
- * Writing patches (tactics)
- When you first distribute a patch it may be suitable to just put forth
- a rough patch, or even just an idea. But before the end of the
- process the following should exist:
- - ChangeLog entry (see the GNU coding standards for details).
- - Changes to the NEWS file and cvs.texinfo, if the change is a
- user-visible change worth mentioning.
- - Somewhere, a description of what the patch fixes (often in
- comments in the code, or maybe the ChangeLog or documentation).
- - Most of the time, a test case (see TESTS). It can be quite
- frustrating to fix a bug only to see it reappear later, and adding
- the case to the testsuite, where feasible, solves this and other
- problems. See the TESTS file for notes on writing new tests.
- If you solve several unrelated problems, it is generally easier to
- consider the desirability of the changes if there is a separate patch
- for each issue. Use context diffs or unidiffs for patches.
- Include words like "I grant permission to distribute this patch under
- the terms of the GNU Public License" with your patch. By sending a
- patch to bug-cvs@gnu.org, you implicitly grant this permission.
- Submitting a patch to bug-cvs is the way to reach the people who have
- signed up to receive such submissions (including CVS developers), but
- there may or may not be much (or any) response. If you want to pursue
- the matter further, you are probably best off working with the larger
- CVS community. Distribute your patch as widely as desired (mailing
- lists, newsgroups, web sites, whatever). Write a web page or other
- information describing what the patch is for. It is neither practical
- nor desirable for all/most contributions to be distributed through the
- "official" (whatever that means) mechanisms of CVS releases and CVS
- developers. Now, the "official" mechanisms do try to incorporate
- those patches which seem most suitable for widespread usage, together
- with test cases and documentation. So if a patch becomes sufficiently
- popular in the CVS community, it is likely that one of the CVS
- developers will eventually try to do something with it. But dealing
- with the CVS developers may be the last step of the process rather
- than the first.
- * What is the schedule for the next release?
- There isn't one. That is, upcoming releases are not announced (or
- even hinted at, really) until the feature freeze which is
- approximately 2 weeks before the final release (at this time test
- releases start appearing and are announced on info-cvs). This is
- intentional, to avoid a last minute rush to get new features in.
- * Mailing lists
- Anyone can add themselves to the following mailing lists:
- dev. Unless you are accepted as a CVS developer as
- described in the DEVEL-CVS file, you will only be able to
- read this list, not send to it. The charter of the list is
- also in DEVEL-CVS.
- cvs. The only messages sent to this list are sent
- automatically, via the CVS `loginfo' mechanism, when someone
- checks something in to the master CVS repository.
- test-results. The only messages sent to this list are sent
- automatically, daily, by a script which runs "make check"
- and "make remotecheck" on the master CVS sources.
- To subscribe to dev, cvs, or test-results, send
- a message to "<list>-subscribe@ccvs.cvshome.org" or visit
- http://ccvs.cvshome.org/servlets/ProjectMailingListList and follow the
- instructions there.
- One other list related to CVS development is bug-cvs. This is the
- list which users are requested to send bug reports to. Anyone can
- subscribe; to do so send mail to bug-cvs-request@gnu.org.
- Other CVS discussions take place on the info-cvs mailing list
- (send mail to info-cvs-request@gnu.org to subscribe) or on
- the newsgroup comp.software.config-mgmt.