Libvirt contributor guidelines ============================== General tips for contributing patches ===================================== (1) Discuss any large changes on the mailing list first. Post patches early and listen to feedback. (2) Post patches in unified diff format. A command similar to this should work: diff -urp libvirt.orig/ libvirt.modified/ > libvirt-myfeature.patch or: cvs diff -up > libvirt-myfeature.patch (3) Split large changes into a series of smaller patches, self-contained if possible, with an explanation of each patch and an explanation of how the sequence of patches fits together. (4) Make sure your patches apply against libvirt CVS. Developers only follow CVS and don't care much about released versions. (5) Run the automated tests on your code before submitting any changes. In particular, configure with compile warnings set to -Werror: ./configure --enable-compile-warnings=error and run the tests: make check make syntax-check make -C tests valgrind The latter test checks for memory leaks. (6) Update tests and/or documentation, particularly if you are adding a new feature or changing the output of a program. There is more on this subject, including lots of links to background reading on the subject, on this page: http://et.redhat.com/~rjones/how-to-supply-code-to-open-source-projects/ Code indentation ================ Libvirt's C source code generally adheres to some basic code-formatting conventions. The existing code base is not totally consistent on this front, but we do prefer that contributed code be formatted similarly. In short, use spaces-not-TABs for indentation, use 4 spaces for each indentation level, and other than that, follow the K&R style. If you use Emacs, add the following to one of one of your start-up files (e.g., ~/.emacs), to help ensure that you get indentation right: ;;; When editing C sources in libvirt, use this style. (defun libvirt-c-mode () "C mode with adjusted defaults for use with libvirt." (interactive) (c-set-style "K&R") (setq indent-tabs-mode nil) ; indent using spaces, not TABs (setq c-indent-level 4) (setq c-basic-offset 4)) (add-hook 'c-mode-hook '(lambda () (if (string-match "/libvirt" (buffer-file-name)) (libvirt-c-mode)))) Code formatting (especially for new code) ========================================= With new code, we can be even more strict. Please apply the following function (using GNU indent) to any new code. Note that this also gives you an idea of the type of spacing we prefer around operators and keywords: indent-libvirt() { indent -bad -bap -bbb -bli4 -br -ce -brs -cs -i4 -l75 -lc75 \ -sbi4 -psl -saf -sai -saw -sbi4 -ss -sc -cdw -cli4 -npcs -nbc \ --no-tabs "$@" } Note that sometimes you'll have to postprocess that output further, by piping it through "expand -i", since some leading TABs can get through. Usually they're in macro definitions or strings, and should be converted anyhow. Low level memory management =========================== Use of the malloc/free/realloc/calloc APIs is deprecated in the libvirt codebase, because they encourage a number of serious coding bugs and do not enable compile time verification of checks for NULL. Instead of these routines, use the macros from memory.h - eg to allocate a single object: virDomainPtr domain; if (VIR_ALLOC(domain) < 0) { __virRaiseError(VIR_ERROR_NO_MEMORY) return NULL; } - eg to allocate an array of objects virDomainPtr domains; int ndomains = 10; if (VIR_ALLOC_N(domains, ndomains) < 0) { __virRaiseError(VIR_ERROR_NO_MEMORY) return NULL; } - eg to allocate an array of object pointers virDomainPtr *domains; int ndomains = 10; if (VIR_ALLOC_N(domains, ndomains) < 0) { __virRaiseError(VIR_ERROR_NO_MEMORY) return NULL; } - eg to re-allocate the array of domains to be longer ndomains = 20 if (VIR_REALLOC_N(domains, ndomains) < 0) { __virRaiseError(VIR_ERROR_NO_MEMORY) return NULL; } - eg to free the domain VIR_FREE(domain); String comparisons ================== Do not use the strcmp, strncmp, etc functions directly. Instead use one of the following semantically named macros - For strict equality: STREQ(a,b) STRNEQ(a,b) - For case sensitive equality: STRCASEEQ(a,b) STRCASENEQ(a,b) - For strict equality of a substring: STREQLEN(a,b,n) STRNEQLEN(a,b,n) - For case sensitive equality of a substring: STRCASEEQLEN(a,b,n) STRCASENEQLEN(a,b,n) - For strict equality of a prefix: STRPREFIX(a,b) Variable length string buffer ============================= If there is a need for complex string concatenations, avoid using the usual sequence of malloc/strcpy/strcat/snprintf functions and make use of the virBuffer API described in buf.h eg typical usage is as follows: char * somefunction(...) { virBuffer buf = VIR_BUFFER_INITIALIZER; ... virBufferAddLit(&buf, "\n"); virBufferVSprint(&buf, " %d\n", memory); ... virBufferAddLit(&buf, "\n"); .... if (virBufferError(&buf)) { __virRaiseError(...); return NULL; } return virBufferContentAndReset(&buf); } Include files ============= There are now quite a large number of include files, both libvirt internal and external, and system includes. To manage all this complexity it's best to stick to the following general plan for all *.c source files: /* * Copyright notice * .... * .... * .... * */ #include Must come first in every file. #include Any system includes you need. #include #include #if HAVE_NUMACTL Some system includes aren't supported #include everywhere so need these #if defences. #endif #include "internal.h" Include this first, after system includes. #include "util.h" Any libvirt internal header files. #include "buf.h" static myInternalFunc () The actual code. { ... Of particular note: *DO NOT* include libvirt/libvirt.h or libvirt/virterror.h. It is included by "internal.h" already and there are some special reasons why you cannot include these files explicitly. Libvirt commiters guidelines ============================ The AUTHORS files indicates the list of people with commit acces right who can actually merge the patches. The general rule for commiting patches is to make sure it has been reviewed properly in the mailing-list first, usually if a couple of persons gave an ACK or +1 to a patch and nobody raised an objection on the list it should be good to go. If the patch touches a part of the code where you're not the main maintainer or not have a very clear idea of how things work, it's better to wait for a more authoritative feedback though. Before commiting please also rebuild locally and run 'make check syntax-check' and make sure they don't raise error. Try to look for warnings too for example configure with --enable-compile-warnings=error which adds -Werror to compile flags, so no warnings get missed Exceptions to that 'review and approval on the list first' is fixing failures to build: - if a recently commited patch breaks compilation on a platform or for a given driver then it's fine to commit a minimal fix directly without getting the review feedback first - similary if make check or make syntax-chek breaks, if there is an obvious fix, it's fine to commit immediately The patch should still be sent to the list (or tell what the fix was if trivial) and 'make check syntax-check' should pass too before commiting anything Similary fixes for documentation and code comments can be managed in the same way, but still make sure they get reviewed if non-trivial.