<ul id="toc"></ul>
<h2><a name="patches">General tips for contributing patches</a></h2>
-
<ol>
<li>Discuss any large changes on the mailing list first. Post patches
early and listen to feedback.</li>
<li><p>Post patches in unified diff format. A command similar to this
should work:</p>
- <pre>
- diff -urp libvirt.orig/ libvirt.modified/ > libvirt-myfeature.patch</pre>
+<pre>
+ diff -urp libvirt.orig/ libvirt.modified/ > libvirt-myfeature.patch
+</pre>
<p>
or:
</p>
- <pre>
- git diff > libvirt-myfeature.patch</pre>
+<pre>
+ git diff > libvirt-myfeature.patch
+</pre>
</li>
<li>Split large changes into a series of smaller patches, self-contained
if possible, with an explanation of each patch and an explanation of how
only follow GIT and don't care much about released versions.</li>
<li><p>Run the automated tests on your code before submitting any changes.
In particular, configure with compile warnings set to -Werror:</p>
- <pre>
- ./configure --enable-compile-warnings=error</pre>
+<pre>
+ ./configure --enable-compile-warnings=error
+</pre>
<p>
and run the tests:
</p>
+<pre>
make check
make syntax-check
- make -C tests valgrind</pre>
+ make -C tests valgrind
+</pre>
<p>
The latter test checks for memory leaks.
</p>
- <p>
- If you encounter any failing tests, the VIR_TEST_DEBUG
- environment variable may provide extra information to debug
- the failures. Larger values of VIR_TEST_DEBUG may provide
- larger amounts of information:
- </p>
+ If you encounter any failing tests, the VIR_TEST_DEBUG
+ environment variable may provide extra information to debug
+ the failures. Larger values of VIR_TEST_DEBUG may provide
+ larger amounts of information:
+ </p>
+<pre>
VIR_TEST_DEBUG=1 make check (or)
- VIR_TEST_DEBUG=2 make check</pre>
- <p>
- Also, individual tests can be run from inside the 'tests/'
- directory, like:
- </p>
- <pre>
- ./qemuxml2xmltest</pre>
+ VIR_TEST_DEBUG=2 make check
+</pre>
+ <p>
+ Also, individual tests can be run from inside the <code>tests/</code>
+ directory, like:
+ </p>
+<pre>
+ ./qemuxml2xmltest
+</pre>
</li>
<li>Update tests and/or documentation, particularly if you are adding
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:
</p>
+<pre>
;;; When editing C sources in libvirt, use this style.
(defun libvirt-c-mode ()
"C mode with adjusted defaults for use with libvirt."
around operators and keywords:
</p>
+<pre>
indent-libvirt()
{
indent -bad -bap -bbb -bli4 -br -ce -brs -cs -i4 -l75 -lc75 \
<p>
Note that sometimes you'll have to post-process that output further, by
- piping it through "expand -i", since some leading TABs can get through.
+ piping it through <code>expand -i</code>, since some leading TABs can get through.
Usually they're in macro definitions or strings, and should be converted
anyhow.
</p>
<h2><a name="curly_braces">Curly braces</a></h2>
<p>
- Omit the curly braces around an "if", "while", "for" etc. body only
+ Omit the curly braces around an <code>if</code>, <code>while</code>,
+ <code>for</code> etc. body only
when that body occupies a single line. In every other case we require
the braces. This ensures that it is trivially easy to identify a
- single-*statement* loop: each has only one *line* in its body.
+ single-<i>statement</i> loop: each has only one <i>line</i> in its body.
</p>
<p>
Omitting braces with a single-line body is fine:
</p>
+<pre>
while (expr) // one-line body -> omitting curly braces is ok
- single_line_stmt ();</pre>
+ single_line_stmt();
+</pre>
<p>
However, the moment your loop/if/else body extends onto a second
it is already a multi-statement loop:
</p>
+<pre>
while (true) // BAD! multi-line body with no braces
/* comment... */
- single_line_stmt ();</pre>
+ single_line_stmt();
+</pre>
<p>
Do this instead:
</p>
+<pre>
while (true) { // Always put braces around a multi-line body.
/* comment... */
- single_line_stmt ();
- }</pre>
+ single_line_stmt();
+ }
+</pre>
<p>
There is one exception: when the second body line is not at the same
indentation level as the first body line:
</p>
+<pre>
if (expr)
- die ("a diagnostic that would make this line"
- " extend past the 80-column limit"));</pre>
+ die("a diagnostic that would make this line"
+ " extend past the 80-column limit"));
+</pre>
<p>
It is safe to omit the braces in the code above, since the
To reiterate, don't do this:
</p>
+<pre>
if (expr) // BAD: no braces around...
while (expr_2) { // ... a multi-line body
...
- }</pre>
+ }
+</pre>
<p>
Do this, instead:
</p>
+<pre>
if (expr) {
while (expr_2) {
...
}
- }</pre>
+ }
+</pre>
<p>
However, there is one exception in the other direction, when even a
one-line block should have braces. That occurs when that one-line,
- brace-less block is an "else" block, and the corresponding "then" block
- *does* use braces. In that case, either put braces around the "else"
- block, or negate the "if"-condition and swap the bodies, putting the
+ brace-less block is an <code>else</code> block, and the corresponding
+ <code>then</code> block <b>does</b> use braces. In that case, either
+ put braces around the <code>else</code> block, or negate the
+ <code>if</code>-condition and swap the bodies, putting the
one-line block first and making the longer, multi-line block be the
- "else" block.
+ <code>else</code> block.
</p>
+<pre>
if (expr) {
...
...
}
else
- x = y; // BAD: braceless "else" with braced "then"</pre>
+ x = y; // BAD: braceless "else" with braced "then"
+</pre>
<p>
This is preferred, especially when the multi-line body is more than a
after the more involved block:
</p>
+<pre>
if (!expr)
x = y; // putting the smaller block first is more readable
else {
...
...
- }</pre>
+ }
+</pre>
<p>
If you'd rather not negate the condition, then at least add braces:
</p>
+<pre>
if (expr) {
...
...
} else {
x = y;
- }</pre>
+ }
+</pre>
<h2><a href="types">Preprocessor</a></h2>
<p>
For variadic macros, stick with C99 syntax:
</p>
+<pre>
#define vshPrint(_ctl, ...) fprintf(stdout, __VA_ARGS__)
- </pre>
+</pre>
<p>Use parenthesis when checking if a macro is defined, and use
indentation to track nesting:
</p>
+<pre>
#if defined(HAVE_POSIX_FALLOCATE) && !defined(HAVE_FALLOCATE)
# define fallocate(a,ignored,b,c) posix_fallocate(a,b,c)
#endif
- </pre>
+</pre>
<h2><a href="types">C types</a></h2>
<h3>Scalars</h3>
<ul>
- <li>If you're using "int" or "long", odds are good that there's a better type.</li>
+ <li>If you're using <code>int</code> or <code>long</code>, odds are
+ good that there's a better type.</li>
<li>If a variable is counting something, be sure to declare it with an
unsigned type.</li>
- <li>If it's memory-size-related, use size_t (use ssize_t only if required).</li>
- <li>If it's file-size related, use uintmax_t, or maybe off_t.</li>
- <li>If it's file-offset related (i.e., signed), use off_t.</li>
- <li>If it's just counting small numbers use "unsigned int";
+ <li>If it's memory-size-related, use <code>size_t</code> (use
+ <code>ssize_t</code> only if required).</li>
+ <li>If it's file-size related, use uintmax_t, or maybe <code>off_t</code>.</li>
+ <li>If it's file-offset related (i.e., signed), use <code>off_t</code>.</li>
+ <li>If it's just counting small numbers use <code>unsigned int</code>;
(on all but oddball embedded systems, you can assume that that
type is at least four bytes wide).</li>
- <li>If a variable has boolean semantics, give it the "bool" type
- and use the corresponding "true" and "false" macros. It's ok
- to include <stdbool.h>, since libvirt's use of gnulib ensures
+ <li>If a variable has boolean semantics, give it the <code>bool</code> type
+ and use the corresponding <code>true</code> and <code>false</code> macros.
+ It's ok to include <stdbool.h>, since libvirt's use of gnulib ensures
that it exists and is usable.</li>
<li>In the unusual event that you require a specific width, use a
- standard type like int32_t, uint32_t, uint64_t, etc.</li>
- <li>While using "bool" is good for readability, it comes with minor caveats:
+ standard type like <code>int32_t</code>, <code>uint32_t</code>,
+ <code>uint64_t</code>, etc.</li>
+ <li>While using <code>bool</code> is good for readability, it comes with
+ minor caveats:
<ul>
- <li>Don't use "bool" in places where the type size must be constant across
+ <li>Don't use <code>bool</code> in places where the type size must be constant across
all systems, like public interfaces and on-the-wire protocols. Note
- that it would be possible (albeit wasteful) to use "bool" in libvirt's
- logical wire protocol, since XDR maps that to its lower-level bool_t
- type, which *is* fixed-size.</li>
- <li>Don't compare a bool variable against the literal, "true",
- since a value with a logical non-false value need not be "1".
- I.e., don't write "if (seen == true) ...". Rather, write "if (seen)...".</li>
+ that it would be possible (albeit wasteful) to use <code>bool</code> in libvirt's
+ logical wire protocol, since XDR maps that to its lower-level <code>bool_t</code>
+ type, which <b>is</b> fixed-size.</li>
+ <li>Don't compare a bool variable against the literal, <code>true</code>,
+ since a value with a logical non-false value need not be <code>1</code>.
+ I.e., don't write <code>if (seen == true) ...</code>. Rather,
+ write <code>if (seen)...</code>.</li>
</ul>
</li>
</ul>
<p>
Of course, take all of the above with a grain of salt. If you're about
- to use some system interface that requires a type like size_t, pid_t or
- off_t, use matching types for any corresponding variables.
+ to use some system interface that requires a type like <code>size_t</code>,
+ <code>pid_t</code> or <code>off_t</code>, use matching types for any
+ corresponding variables.
</p>
<p>
- Also, if you try to use e.g., "unsigned int" as a type, and that
+ Also, if you try to use e.g., <code>unsigned int</code> as a type, and that
conflicts with the signedness of a related variable, sometimes
- it's best just to use the *wrong* type, if "pulling the thread"
+ it's best just to use the <b>wrong</b> type, if <i>pulling the thread</i>
and fixing all related variables would be too invasive.
</p>
<h3>Pointers</h3>
<p>
- Ensure that all of your pointers are "const-correct".
+ Ensure that all of your pointers are <i>const-correct</i>.
Unless a pointer is used to modify the pointed-to storage,
- give it the "const" attribute. That way, the reader knows
+ give it the <code>const</code> attribute. That way, the reader knows
up-front that this is a read-only pointer. Perhaps more
importantly, if we're diligent about this, when you see a non-const
pointer, you're guaranteed that it is used to modify the storage
</p>
<ul>
- <li><p>eg to allocate a single object:</p>
-
+ <li><p>e.g. to allocate a single object:</p>
<pre>
- virDomainPtr domain;
+ virDomainPtr domain;
- if (VIR_ALLOC(domain) < 0) {
- virReportOOMError();
- return NULL;
- }
-</pre></li>
-
- <li><p>eg to allocate an array of objects</p>
+ if (VIR_ALLOC(domain) < 0) {
+ virReportOOMError();
+ return NULL;
+ }
+</pre>
+ </li>
+ <li><p>e.g. to allocate an array of objects</p>
<pre>
- virDomainPtr domains;
- int ndomains = 10;
-
- if (VIR_ALLOC_N(domains, ndomains) < 0) {
- virReportOOMError();
- return NULL;
- }
-</pre></li>
+ virDomainPtr domains;
+ int ndomains = 10;
- <li><p>eg to allocate an array of object pointers</p>
+ if (VIR_ALLOC_N(domains, ndomains) < 0) {
+ virReportOOMError();
+ return NULL;
+ }
+</pre>
+ </li>
+ <li><p>e.g. to allocate an array of object pointers</p>
<pre>
- virDomainPtr *domains;
- int ndomains = 10;
+ virDomainPtr *domains;
+ int ndomains = 10;
- if (VIR_ALLOC_N(domains, ndomains) < 0) {
- virReportOOMError();
- return NULL;
- }
-</pre></li>
-
- <li><p>eg to re-allocate the array of domains to be longer</p>
+ if (VIR_ALLOC_N(domains, ndomains) < 0) {
+ virReportOOMError();
+ return NULL;
+ }
+</pre>
+ </li>
+ <li><p>e.g. to re-allocate the array of domains to be longer</p>
<pre>
- ndomains = 20
-
- if (VIR_REALLOC_N(domains, ndomains) < 0) {
- virReportOOMError();
- return NULL;
- }
-</pre></li>
+ ndomains = 20
- <li><p>eg to free the domain</p>
+ if (VIR_REALLOC_N(domains, ndomains) < 0) {
+ virReportOOMError();
+ return NULL;
+ }
+</pre>
+ </li>
+ <li><p>e.g. to free the domain</p>
<pre>
- VIR_FREE(domain);
-</pre></li>
+ VIR_FREE(domain);
+</pre>
+ </li>
</ul>
<h2><a name="file_handling">File handling</a></h2>
</p>
<ul>
- <li><p>eg close a file descriptor</p>
-
+ <li><p>e.g. close a file descriptor</p>
<pre>
- if (VIR_CLOSE(fd) < 0) {
- virReportSystemError(errno, _("failed to close file"));
- }
-</pre></li>
+ if (VIR_CLOSE(fd) < 0) {
+ virReportSystemError(errno, _("failed to close file"));
+ }
+</pre>
+ </li>
<li><p>eg close a file descriptor in an error path, without losing
- the previous errno value</p>
+ the previous <code>errno</code> value</p>
<pre>
- VIR_FORCE_CLOSE(fd);
-</pre></li>
+ VIR_FORCE_CLOSE(fd);
+</pre>
+ </li>
</ul>
<h2><a name="string_comparision">String comparisons</a></h2>
<ul>
<li><p>For strict equality:</p>
- STREQ(a,b)
- STRNEQ(a,b)
+<pre>
+ STREQ(a,b)
+ STRNEQ(a,b)
</pre>
</li>
<li><p>For case insensitive equality:</p>
- STRCASEEQ(a,b)
- STRCASENEQ(a,b)
+<pre>
+ STRCASEEQ(a,b)
+ STRCASENEQ(a,b)
</pre>
</li>
<li><p>For strict equality of a substring:</p>
-
- <pre>
- STREQLEN(a,b,n)
- STRNEQLEN(a,b,n)
+<pre>
+ STREQLEN(a,b,n)
+ STRNEQLEN(a,b,n)
</pre>
</li>
<li><p>For case insensitive equality of a substring:</p>
-
- <pre>
- STRCASEEQLEN(a,b,n)
- STRCASENEQLEN(a,b,n)
+<pre>
+ STRCASEEQLEN(a,b,n)
+ STRCASENEQLEN(a,b,n)
</pre>
</li>
<li><p>For strict equality of a prefix:</p>
-
- <pre>
- STRPREFIX(a,b)
+<pre>
+ STRPREFIX(a,b)
</pre>
</li>
</ul>
it extremely dangerous to use. Instead, use one of the
functionally equivalent functions:
</p>
- <pre>virStrncpy(char *dest, const char *src, size_t n, size_t destbytes)</pre>
+
+<pre>
+ virStrncpy(char *dest, const char *src, size_t n, size_t destbytes)
+</pre>
<p>
The first three arguments have the same meaning as for strncpy;
namely the destination, source, and number of bytes to copy,
trailing \0 is appended.
</p>
- <pre>virStrcpy(char *dest, const char *src, size_t destbytes)</pre>
-
+<pre>
+ virStrcpy(char *dest, const char *src, size_t destbytes)
+</pre>
<p>
Use this variant if you know you want to copy the entire src
string into dest. Note that this is a macro, so arguments could
virStrncpy(dest, src, strlen(src), destbytes)
</p>
- <pre>virStrcpyStatic(char *dest, const char *src)</pre>
-
+<pre>
+ virStrcpyStatic(char *dest, const char *src)
+</pre>
<p>
Use this variant if you know you want to copy the entire src
- string into dest *and* you know that your destination string is
+ string into dest <b>and</b> you know that your destination string is
a static string (i.e. that sizeof(dest) returns something
meaningful). Note that this is a macro, so arguments could be
evaluated more than once. This is equivalent to
<p>eg typical usage is as follows:</p>
+<pre>
char *
- somefunction(...) {
+ somefunction(...)
+ {
virBuffer buf = VIR_BUFFER_INITIALIZER;
...
*.c source files:
</p>
+<pre>
/*
* Copyright notice
* ....
#include <limits.h>
#if HAVE_NUMACTL Some system includes aren't supported
- # include <numa.h> everywhere so need these #if guards.
+ # include <numa.h> everywhere so need these #if guards.
#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.
+ static int
+ myInternalFunc() The actual code.
{
- ...
+ ...
</pre>
<p>
- Of particular note: *DO NOT* include libvirt/libvirt.h or
+ Of particular note: <b>Do not</b> 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.
the one for virAsprintf, in util.h:
</p>
- int virAsprintf(char **strp, const char *fmt, ...)
- ATTRIBUTE_FORMAT(printf, 2, 3);
+<pre>
+ int virAsprintf(char **strp, const char *fmt, ...)
+ ATTRIBUTE_FORMAT(printf, 2, 3);
</pre>
<p>
Although libvirt does not encourage the Linux kernel wind/unwind
style of multiple labels, there's a good general discussion of
the issue archived at
- <a href=http://kerneltrap.org/node/553/2131>KernelTrap</a>
+ <a href="http://kerneltrap.org/node/553/2131">KernelTrap</a>
</p>
<p>
makes sense:
</p>
+<pre>
error: A path only taken upon return with an error code
cleanup: A path taken upon return with success code + optional error
no_memory: A path only taken upon return with an OOM error code
- retry: If needing to jump upwards (eg retry on EINTR)</pre>
+ retry: If needing to jump upwards (eg retry on EINTR)
+</pre>
configure with
</p>
<pre>
- --enable-compile-warnings=error
+ --enable-compile-warnings=error
</pre>
<p>
which adds -Werror to compile flags, so no warnings get missed
projects / libvirt.git / commitdiff