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161 lines
4.0 KiB
Plaintext
161 lines
4.0 KiB
Plaintext
Libvirt contributor guidelines
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==============================
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Code indentation
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================
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Libvirt's C source code generally adheres to some basic code-formatting
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conventions. The existing code base is not totally consistent on this
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front, but we do prefer that contributed code be formatted similarly.
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In short, use spaces-not-TABs for indentation, use 4 spaces for each
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indentation level, and other than that, follow the K&R style.
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If you use Emacs, add the following to one of one of your start-up files
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(e.g., ~/.emacs), to help ensure that you get indentation right:
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;;; When editing C sources in libvirt, use this style.
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(defun libvirt-c-mode ()
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"C mode with adjusted defaults for use with libvirt."
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(interactive)
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(c-set-style "K&R")
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(setq indent-tabs-mode nil) ; indent using spaces, not TABs
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(setq c-indent-level 4)
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(setq c-basic-offset 4))
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(add-hook 'c-mode-hook
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'(lambda () (if (string-match "/libvirt" (buffer-file-name))
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(libvirt-c-mode))))
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Code formatting (especially for new code)
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=========================================
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With new code, we can be even more strict.
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Please apply the following function (using GNU indent) to any new code.
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Note that this also gives you an idea of the type of spacing we prefer
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around operators and keywords:
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indent-libvirt()
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{
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indent -bad -bap -bbb -bli4 -br -ce -brs -cs -i4 -l75 -lc75 \
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-sbi4 -psl -saf -sai -saw -sbi4 -ss -sc -cdw -cli4 -npcs -nbc \
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--no-tabs "$@"
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}
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Note that sometimes you'll have to postprocess that output further, by
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piping it through "expand -i", since some leading TABs can get through.
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Usually they're in macro definitions or strings, and should be converted
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anyhow.
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Low level memory management
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===========================
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Use of the malloc/free/realloc/calloc APIs is deprecated in the libvirt
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codebase, because they encourage a number of serious coding bugs and do
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not enable compile time verification of checks for NULL. Instead of these
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routines, use the macros from memory.h
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- eg to allocate a single object:
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virDomainPtr domain;
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if (VIR_ALLOC(domain) < 0) {
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__virRaiseError(VIR_ERROR_NO_MEMORY)
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return NULL;
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}
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- eg to allocate an array of objects
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virDomainPtr domains;
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int ndomains = 10;
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if (VIR_ALLOC_N(domains, ndomains) < 0) {
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__virRaiseError(VIR_ERROR_NO_MEMORY)
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return NULL;
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}
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- eg to allocate an array of object pointers
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virDomainPtr *domains;
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int ndomains = 10;
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if (VIR_ALLOC_N(domains, ndomains) < 0) {
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__virRaiseError(VIR_ERROR_NO_MEMORY)
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return NULL;
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}
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- eg to re-allocate the array of domains to be longer
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ndomains = 20
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if (VIR_REALLOC_N(domains, ndomains) < 0) {
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__virRaiseError(VIR_ERROR_NO_MEMORY)
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return NULL;
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}
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- eg to free the domain
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VIR_FREE(domain);
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String comparisons
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==================
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Do not use the strcmp, strncmp, etc functions directly. Instead use
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one of the following semantically named macros
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- For strict equality:
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STREQ(a,b)
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STRNEQ(a,b)
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- For case sensitive equality:
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STRCASEEQ(a,b)
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STRCASENEQ(a,b)
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- For strict equality of a substring:
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STREQLEN(a,b,n)
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STRNEQLEN(a,b,n)
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- For case sensitive equality of a substring:
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STRCASEEQLEN(a,b,n)
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STRCASENEQLEN(a,b,n)
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- For strict equality of a prefix:
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STRPREFIX(a,b)
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Variable length string buffer
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=============================
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If there is a need for complex string concatenations, avoid using
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the usual sequence of malloc/strcpy/strcat/snprintf functions and
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make use of the virBuffer API described in buf.h
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eg typical usage is as follows:
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char *
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somefunction(...) {
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virBuffer buf = VIR_BUFFER_INITIALIZER;
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...
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virBufferAddLit(&buf, "<domain>\n");
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virBufferVSprint(&buf, " <memory>%d</memory>\n", memory);
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...
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virBufferAddLit(&buf, "</domain>\n");
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....
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if (virBufferError(&buf)) {
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__virRaiseError(...);
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return NULL;
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}
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return virBufferContentAndReset(&buf);
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}
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