openkylin
/
libvirt
mirror of https://gitee.com/openkylin/libvirt.git
9
0
Fork 0
Code Issues Projects Releases Wiki Activity

docs: Prepare hacking.html.in to generate HACKING from it 

Tweak pre tags to achieve proper indentation of their
plaintext representation. Also use more b/i/code tags.
This commit is contained in:
Matthias Bolte 2010-11-12 15:33:00 +01:00
parent 4302b3f8f0
commit d39620e367
1 changed files with 191 additions and 163 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

254
docs/hacking.html.in
View File

@ -5,20 +5,21 @@
<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/ &gt; libvirt-myfeature.patch</pre>
<pre>
diff -urp libvirt.orig/ libvirt.modified/ &gt; 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
@ -27,15 +28,17 @@
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>
<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>
@ -47,15 +50,17 @@
larger amounts of information:
</p>
<pre>
<pre>
VIR_TEST_DEBUG=1 make check (or)
VIR_TEST_DEBUG=2 make check</pre>
VIR_TEST_DEBUG=2 make check
</pre>
<p>
Also, individual tests can be run from inside the 'tests/'
Also, individual tests can be run from inside the <code>tests/</code>
directory, like:
</p>
<pre>
./qemuxml2xmltest</pre>
<pre>
./qemuxml2xmltest
</pre>
</li>
<li>Update tests and/or documentation, particularly if you are adding
@ -82,7 +87,7 @@
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>
<pre>
;;; When editing C sources in libvirt, use this style.
(defun libvirt-c-mode ()
"C mode with adjusted defaults for use with libvirt."
@ -105,7 +110,7 @@
around operators and keywords:
</p>
<pre>
<pre>
indent-libvirt()
{
indent -bad -bap -bbb -bli4 -br -ce -brs -cs -i4 -l75 -lc75 \
@ -116,7 +121,7 @@
<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>
@ -125,18 +130,20 @@
<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>
<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
@ -146,26 +153,29 @@
it is already a multi-statement loop:
</p>
<pre>
<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>
<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>
<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
@ -177,40 +187,44 @@
To reiterate, don't do this:
</p>
<pre>
<pre>
if (expr) // BAD: no braces around...
while (expr_2) { // ... a multi-line body
...
}</pre>
}
</pre>
<p>
Do this, instead:
</p>
<pre>
<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>
<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
@ -219,43 +233,45 @@
after the more involved block:
</p>
<pre>
<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>
<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>
<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>
<pre>
#if defined(HAVE_POSIX_FALLOCATE) &amp;&amp; !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>
@ -266,45 +282,51 @@
<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 &lt;stdbool.h&gt;, 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 &lt;stdbool.h&gt;, 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>
@ -317,9 +339,9 @@
<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
@ -336,8 +358,7 @@
</p>
<ul>
<li><p>eg to allocate a single object:</p>
<li><p>e.g. to allocate a single object:</p>
<pre>
virDomainPtr domain;
@ -345,10 +366,10 @@
virReportOOMError();
return NULL;
}
</pre></li>
<li><p>eg to allocate an array of objects</p>
</pre>
</li>
<li><p>e.g. to allocate an array of objects</p>
<pre>
virDomainPtr domains;
int ndomains = 10;
@ -357,10 +378,10 @@
virReportOOMError();
return NULL;
}
</pre></li>
<li><p>eg to allocate an array of object pointers</p>
</pre>
</li>
<li><p>e.g. to allocate an array of object pointers</p>
<pre>
virDomainPtr *domains;
int ndomains = 10;
@ -369,10 +390,10 @@
virReportOOMError();
return NULL;
}
</pre></li>
<li><p>eg to re-allocate the array of domains to be longer</p>
</pre>
</li>
<li><p>e.g. to re-allocate the array of domains to be longer</p>
<pre>
ndomains = 20
@ -380,13 +401,14 @@
virReportOOMError();
return NULL;
}
</pre></li>
<li><p>eg to free the domain</p>
</pre>
</li>
<li><p>e.g. to free the domain</p>
<pre>
VIR_FREE(domain);
</pre></li>
</pre>
</li>
</ul>
<h2><a name="file_handling">File handling</a></h2>
@ -398,20 +420,21 @@
</p>
<ul>
<li><p>eg close a file descriptor</p>
<li><p>e.g. close a file descriptor</p>
<pre>
if (VIR_CLOSE(fd) &lt; 0) {
virReportSystemError(errno, _("failed to close file"));
}
</pre></li>
</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>
</pre>
</li>
</ul>
<h2><a name="string_comparision">String comparisons</a></h2>
@ -423,38 +446,35 @@
<ul>
<li><p>For strict equality:</p>
<pre>
<pre>
STREQ(a,b)
STRNEQ(a,b)
</pre>
</li>
<li><p>For case insensitive equality:</p>
<pre>
<pre>
STRCASEEQ(a,b)
STRCASENEQ(a,b)
</pre>
</li>
<li><p>For strict equality of a substring:</p>
<pre>
<pre>
STREQLEN(a,b,n)
STRNEQLEN(a,b,n)
</pre>
</li>
<li><p>For case insensitive equality of a substring:</p>
<pre>
<pre>
STRCASEEQLEN(a,b,n)
STRCASENEQLEN(a,b,n)
</pre>
</li>
<li><p>For strict equality of a prefix:</p>
<pre>
<pre>
STRPREFIX(a,b)
</pre>
</li>
@ -469,7 +489,10 @@
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,
@ -481,8 +504,9 @@
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
@ -490,11 +514,12 @@
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
@ -511,9 +536,10 @@
<p>eg typical usage is as follows:</p>
<pre>
<pre>
char *
somefunction(...) {
somefunction(...)
{
virBuffer buf = VIR_BUFFER_INITIALIZER;
...
@ -545,7 +571,7 @@
*.c source files:
</p>
<pre>
<pre>
/*
* Copyright notice
* ....
@ -569,13 +595,14 @@
#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.
@ -591,7 +618,7 @@
the one for virAsprintf, in util.h:
</p>
<pre>
<pre>
int virAsprintf(char **strp, const char *fmt, ...)
ATTRIBUTE_FORMAT(printf, 2, 3);
</pre>
@ -654,7 +681,7 @@
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>
@ -662,11 +689,12 @@
makes sense:
</p>
<pre>
<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>