* [Qemu-devel] [PULL 1/4] docs: convert README, CODING_STYLE and HACKING to RST syntax
2019-09-05 13:45 [Qemu-devel] [PULL 0/4] Docs patches Daniel P. Berrangé
@ 2019-09-05 13:45 ` Daniel P. Berrangé
2019-09-05 13:45 ` [Qemu-devel] [PULL 2/4] docs: merge HACKING.rst contents into CODING_STYLE.rst Daniel P. Berrangé
` (4 subsequent siblings)
5 siblings, 0 replies; 9+ messages in thread
From: Daniel P. Berrangé @ 2019-09-05 13:45 UTC (permalink / raw)
To: qemu-devel
Cc: Peter Maydell, Daniel P. Berrangé,
Marc-André Lureau, Stefan Hajnoczi, Alex Bennée
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
---
CODING_STYLE => CODING_STYLE.rst | 121 +++++++++++++++++++-----------
HACKING => HACKING.rst | 123 +++++++++++++++++++++----------
README => README.rst | 47 +++++++-----
scripts/checkpatch.pl | 2 +-
4 files changed, 191 insertions(+), 102 deletions(-)
rename CODING_STYLE => CODING_STYLE.rst (72%)
rename HACKING => HACKING.rst (79%)
rename README => README.rst (84%)
diff --git a/CODING_STYLE b/CODING_STYLE.rst
similarity index 72%
rename from CODING_STYLE
rename to CODING_STYLE.rst
index cb8edcbb36..713357cb80 100644
--- a/CODING_STYLE
+++ b/CODING_STYLE.rst
@@ -1,10 +1,14 @@
+=================
QEMU Coding Style
=================
+.. contents:: Table of Contents
+
Please use the script checkpatch.pl in the scripts directory to check
patches before submitting.
-1. Whitespace
+Whitespace
+==========
Of course, the most important aspect in any coding style is whitespace.
Crusty old coders who have trouble spotting the glasses on their noses
@@ -16,26 +20,27 @@ QEMU indents are four spaces. Tabs are never used, except in Makefiles
where they have been irreversibly coded into the syntax.
Spaces of course are superior to tabs because:
- - You have just one way to specify whitespace, not two. Ambiguity breeds
- mistakes.
- - The confusion surrounding 'use tabs to indent, spaces to justify' is gone.
- - Tab indents push your code to the right, making your screen seriously
- unbalanced.
- - Tabs will be rendered incorrectly on editors who are misconfigured not
- to use tab stops of eight positions.
- - Tabs are rendered badly in patches, causing off-by-one errors in almost
- every line.
- - It is the QEMU coding style.
+* You have just one way to specify whitespace, not two. Ambiguity breeds
+ mistakes.
+* The confusion surrounding 'use tabs to indent, spaces to justify' is gone.
+* Tab indents push your code to the right, making your screen seriously
+ unbalanced.
+* Tabs will be rendered incorrectly on editors who are misconfigured not
+ to use tab stops of eight positions.
+* Tabs are rendered badly in patches, causing off-by-one errors in almost
+ every line.
+* It is the QEMU coding style.
Do not leave whitespace dangling off the ends of lines.
-1.1 Multiline Indent
+Multiline Indent
+----------------
There are several places where indent is necessary:
- - if/else
- - while/for
- - function definition & call
+* if/else
+* while/for
+* function definition & call
When breaking up a long line to fit within line width, we need a proper indent
for the following lines.
@@ -45,6 +50,8 @@ opening parenthesis of the first.
For example:
+.. code-block:: c
+
if (a == 1 &&
b == 2) {
@@ -53,12 +60,13 @@ For example:
In case of function, there are several variants:
- * 4 spaces indent from the beginning
- * align the secondary lines just after the opening parenthesis of the
- first
+* 4 spaces indent from the beginning
+* align the secondary lines just after the opening parenthesis of the first
For example:
+.. code-block:: c
+
do_something(x, y,
z);
@@ -68,7 +76,8 @@ For example:
do_something(x, do_another(y,
z));
-2. Line width
+Line width
+==========
Lines should be 80 characters; try not to make them longer.
@@ -77,16 +86,18 @@ that use long function or symbol names. Even in that case, do not make
lines much longer than 80 characters.
Rationale:
- - Some people like to tile their 24" screens with a 6x4 matrix of 80x24
- xterms and use vi in all of them. The best way to punish them is to
- let them keep doing it.
- - Code and especially patches is much more readable if limited to a sane
- line length. Eighty is traditional.
- - The four-space indentation makes the most common excuse ("But look
- at all that white space on the left!") moot.
- - It is the QEMU coding style.
-3. Naming
+* Some people like to tile their 24" screens with a 6x4 matrix of 80x24
+ xterms and use vi in all of them. The best way to punish them is to
+ let them keep doing it.
+* Code and especially patches is much more readable if limited to a sane
+ line length. Eighty is traditional.
+* The four-space indentation makes the most common excuse ("But look
+ at all that white space on the left!") moot.
+* It is the QEMU coding style.
+
+Naming
+======
Variables are lower_case_with_underscores; easy to type and read. Structured
type names are in CamelCase; harder to type but standing out. Enum type
@@ -95,10 +106,11 @@ names are lower_case_with_underscores_ending_with_a_t, like the POSIX
uint64_t and family. Note that this last convention contradicts POSIX
and is therefore likely to be changed.
-When wrapping standard library functions, use the prefix qemu_ to alert
+When wrapping standard library functions, use the prefix ``qemu_`` to alert
readers that they are seeing a wrapped version; otherwise avoid this prefix.
-4. Block structure
+Block structure
+===============
Every indented statement is braced; even if the block contains just one
statement. The opening brace is on the line that contains the control
@@ -106,6 +118,8 @@ flow statement that introduces the new block; the closing brace is on the
same line as the else keyword, or on a line by itself if there is no else
keyword. Example:
+.. code-block:: c
+
if (a == 5) {
printf("a was 5.\n");
} else if (a == 6) {
@@ -121,6 +135,8 @@ statement.
An exception is the opening brace for a function; for reasons of tradition
and clarity it comes on a line by itself:
+.. code-block:: c
+
void a_function(void)
{
do_something();
@@ -130,7 +146,8 @@ Rationale: a consistent (except for functions...) bracing style reduces
ambiguity and avoids needless churn when lines are added or removed.
Furthermore, it is the QEMU coding style.
-5. Declarations
+Declarations
+============
Mixed declarations (interleaving statements and declarations within
blocks) are generally not allowed; declarations should be at the beginning
@@ -142,11 +159,14 @@ be placed at the top of the block even if there are statements above.
On the other hand, however, it's often best to move that #ifdef/#ifndef
block to a separate function altogether.
-6. Conditional statements
+Conditional statements
+======================
When comparing a variable for (in)equality with a constant, list the
constant on the right, as in:
+.. code-block:: c
+
if (a == 1) {
/* Reads like: "If a equals 1" */
do_something();
@@ -156,19 +176,24 @@ Rationale: Yoda conditions (as in 'if (1 == a)') are awkward to read.
Besides, good compilers already warn users when '==' is mis-typed as '=',
even when the constant is on the right.
-7. Comment style
+Comment style
+=============
-We use traditional C-style /* */ comments and avoid // comments.
+We use traditional C-style /``*`` ``*``/ comments and avoid // comments.
Rationale: The // form is valid in C99, so this is purely a matter of
consistency of style. The checkpatch script will warn you about this.
Multiline comment blocks should have a row of stars on the left,
-and the initial /* and terminating */ both on their own lines:
+and the initial /``*`` and terminating ``*``/ both on their own lines:
+
+.. code-block:: c
+
/*
* like
* this
*/
+
This is the same format required by the Linux kernel coding style.
(Some of the existing comments in the codebase use the GNU Coding
@@ -180,24 +205,32 @@ comment anyway.)
Rationale: Consistency, and ease of visually picking out a multiline
comment from the surrounding code.
-8. trace-events style
+trace-events style
+==================
-8.1 0x prefix
+0x prefix
+---------
In trace-events files, use a '0x' prefix to specify hex numbers, as in:
-some_trace(unsigned x, uint64_t y) "x 0x%x y 0x" PRIx64
+.. code-block::
+
+ some_trace(unsigned x, uint64_t y) "x 0x%x y 0x" PRIx64
An exception is made for groups of numbers that are hexadecimal by
convention and separated by the symbols '.', '/', ':', or ' ' (such as
PCI bus id):
-another_trace(int cssid, int ssid, int dev_num) "bus id: %x.%x.%04x"
+.. code-block::
+
+ another_trace(int cssid, int ssid, int dev_num) "bus id: %x.%x.%04x"
However, you can use '0x' for such groups if you want. Anyway, be sure that
it is obvious that numbers are in hex, ex.:
-data_dump(uint8_t c1, uint8_t c2, uint8_t c3) "bytes (in hex): %02x %02x %02x"
+.. code-block::
+
+ data_dump(uint8_t c1, uint8_t c2, uint8_t c3) "bytes (in hex): %02x %02x %02x"
Rationale: hex numbers are hard to read in logs when there is no 0x prefix,
especially when (occasionally) the representation doesn't contain any letters
@@ -205,12 +238,14 @@ and especially in one line with other decimal numbers. Number groups are allowed
to not use '0x' because for some things notations like %x.%x.%x are used not
only in Qemu. Also dumping raw data bytes with '0x' is less readable.
-8.2 '#' printf flag
+'#' printf flag
+---------------
Do not use printf flag '#', like '%#x'.
Rationale: there are two ways to add a '0x' prefix to printed number: '0x%...'
and '%#...'. For consistency the only one way should be used. Arguments for
'0x%' are:
- - it is more popular
- - '%#' omits the 0x for the value 0 which makes output inconsistent
+
+* it is more popular
+* '%#' omits the 0x for the value 0 which makes output inconsistent
diff --git a/HACKING b/HACKING.rst
similarity index 79%
rename from HACKING
rename to HACKING.rst
index 097d482603..668fc420c3 100644
--- a/HACKING
+++ b/HACKING.rst
@@ -1,19 +1,32 @@
-1. Preprocessor
+============
+QEMU Hacking
+============
-1.1. Variadic macros
+.. contents:: Table of Contents
+
+Preprocessor
+============
+
+Variadic macros
+---------------
For variadic macros, stick with this C99-like syntax:
-#define DPRINTF(fmt, ...) \
- do { printf("IRQ: " fmt, ## __VA_ARGS__); } while (0)
+.. code-block:: c
-1.2. Include directives
+ #define DPRINTF(fmt, ...) \
+ do { printf("IRQ: " fmt, ## __VA_ARGS__); } while (0)
+
+Include directives
+------------------
Order include directives as follows:
-#include "qemu/osdep.h" /* Always first... */
-#include <...> /* then system headers... */
-#include "..." /* and finally QEMU headers. */
+.. code-block:: c
+
+ #include "qemu/osdep.h" /* Always first... */
+ #include <...> /* then system headers... */
+ #include "..." /* and finally QEMU headers. */
The "qemu/osdep.h" header contains preprocessor macros that affect the behavior
of core system headers like <stdint.h>. It must be the first include so that
@@ -23,12 +36,14 @@ that QEMU depends on.
Do not include "qemu/osdep.h" from header files since the .c file will have
already included it.
-2. C types
+C types
+=======
It should be common sense to use the right type, but we have collected
a few useful guidelines here.
-2.1. Scalars
+Scalars
+-------
If you're using "int" or "long", odds are good that there's a better type.
If a variable is counting something, it should be declared with an
@@ -68,8 +83,8 @@ it may be 32 or 64 bits depending on which target is being built. It should
therefore be used only in target-specific code, and in some
performance-critical built-per-target core code such as the TLB code.
There is also a signed version, target_long.
-abi_ulong is for the *-user targets, and represents a type the size of
-'void *' in that target's ABI. (This may not be the same as the size of a
+abi_ulong is for the ``*``-user targets, and represents a type the size of
+'void ``*``' in that target's ABI. (This may not be the same as the size of a
full CPU virtual address in the case of target ABIs which use 32 bit pointers
on 64 bit CPUs, like sparc32plus.) Definitions of structures that must match
the target's ABI must use this type for anything that on the target is defined
@@ -89,7 +104,8 @@ Finally, while using descriptive types is important, be careful not to
go overboard. If whatever you're doing causes warnings, or requires
casts, then reconsider or ask for help.
-2.2. Pointers
+Pointers
+--------
Ensure that all of your pointers are "const-correct".
Unless a pointer is used to modify the pointed-to storage,
@@ -99,7 +115,8 @@ 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
it points to, or it is aliased to another pointer that is.
-2.3. Typedefs
+Typedefs
+--------
Typedefs are used to eliminate the redundant 'struct' keyword, since type
names have a different style than other identifiers ("CamelCase" versus
@@ -114,11 +131,14 @@ definitions instead of typedefs in headers and function prototypes; this
avoids problems with duplicated typedefs and reduces the need to include
headers from other headers.
-2.4. Reserved namespaces in C and POSIX
+Reserved namespaces in C and POSIX
+----------------------------------
+
Underscore capital, double underscore, and underscore 't' suffixes should be
avoided.
-3. Low level memory management
+Low level memory management
+===========================
Use of the malloc/free/realloc/calloc/valloc/memalign/posix_memalign
APIs is not allowed in the QEMU codebase. Instead of these routines,
@@ -130,36 +150,51 @@ Please note that g_malloc will exit on allocation failure, so there
is no need to test for failure (as you would have to with malloc).
Calling g_malloc with a zero size is valid and will return NULL.
-Prefer g_new(T, n) instead of g_malloc(sizeof(T) * n) for the following
+Prefer g_new(T, n) instead of g_malloc(sizeof(T) ``*`` n) for the following
reasons:
- a. It catches multiplication overflowing size_t;
- b. It returns T * instead of void *, letting compiler catch more type
- errors.
+* It catches multiplication overflowing size_t;
+* It returns T ``*`` instead of void ``*``, letting compiler catch more type errors.
+
+Declarations like
+
+.. code-block:: c
+
+ T *v = g_malloc(sizeof(*v))
-Declarations like T *v = g_malloc(sizeof(*v)) are acceptable, though.
+are acceptable, though.
Memory allocated by qemu_memalign or qemu_blockalign must be freed with
qemu_vfree, since breaking this will cause problems on Win32.
-4. String manipulation
+String manipulation
+===================
Do not use the strncpy function. As mentioned in the man page, it does *not*
guarantee a NULL-terminated buffer, which makes it extremely dangerous to use.
It also zeros trailing destination bytes out to the specified length. Instead,
use this similar function when possible, but note its different signature:
-void pstrcpy(char *dest, int dest_buf_size, const char *src)
+
+.. code-block:: c
+
+ void pstrcpy(char *dest, int dest_buf_size, const char *src)
Don't use strcat because it can't check for buffer overflows, but:
-char *pstrcat(char *buf, int buf_size, const char *s)
+
+.. code-block:: c
+
+ char *pstrcat(char *buf, int buf_size, const char *s)
The same limitation exists with sprintf and vsprintf, so use snprintf and
vsnprintf.
QEMU provides other useful string functions:
-int strstart(const char *str, const char *val, const char **ptr)
-int stristart(const char *str, const char *val, const char **ptr)
-int qemu_strnlen(const char *s, int max_len)
+
+.. code-block:: c
+
+ int strstart(const char *str, const char *val, const char **ptr)
+ int stristart(const char *str, const char *val, const char **ptr)
+ int qemu_strnlen(const char *s, int max_len)
There are also replacement character processing macros for isxyz and toxyz,
so instead of e.g. isalnum you should use qemu_isalnum.
@@ -167,7 +202,8 @@ so instead of e.g. isalnum you should use qemu_isalnum.
Because of the memory management rules, you must use g_strdup/g_strndup
instead of plain strdup/strndup.
-5. Printf-style functions
+Printf-style functions
+======================
Whenever you add a new printf-style function, i.e., one with a format
string argument and following "..." in its prototype, be sure to use
@@ -177,12 +213,14 @@ This makes it so gcc's -Wformat and -Wformat-security options can do
their jobs and cross-check format strings with the number and types
of arguments.
-6. C standard, implementation defined and undefined behaviors
+C standard, implementation defined and undefined behaviors
+==========================================================
C code in QEMU should be written to the C99 language specification. A copy
of the final version of the C99 standard with corrigenda TC1, TC2, and TC3
included, formatted as a draft, can be downloaded from:
- http://www.open-std.org/jtc1/sc22/WG14/www/docs/n1256.pdf
+
+ `<http://www.open-std.org/jtc1/sc22/WG14/www/docs/n1256.pdf>`_
The C language specification defines regions of undefined behavior and
implementation defined behavior (to give compiler authors enough leeway to
@@ -193,17 +231,20 @@ argument...) However there are a few areas where we allow ourselves to
assume certain behaviors because in practice all the platforms we care about
behave in the same way and writing strictly conformant code would be
painful. These are:
- * you may assume that integers are 2s complement representation
- * you may assume that right shift of a signed integer duplicates
- the sign bit (ie it is an arithmetic shift, not a logical shift)
+
+* you may assume that integers are 2s complement representation
+* you may assume that right shift of a signed integer duplicates
+ the sign bit (ie it is an arithmetic shift, not a logical shift)
In addition, QEMU assumes that the compiler does not use the latitude
given in C99 and C11 to treat aspects of signed '<<' as undefined, as
documented in the GNU Compiler Collection manual starting at version 4.0.
-7. Error handling and reporting
+Error handling and reporting
+============================
-7.1 Reporting errors to the human user
+Reporting errors to the human user
+----------------------------------
Do not use printf(), fprintf() or monitor_printf(). Instead, use
error_report() or error_vreport() from error-report.h. This ensures the
@@ -214,10 +255,11 @@ Use error_printf() & friends to print additional information.
error_report() prints the current location. In certain common cases
like command line parsing, the current location is tracked
-automatically. To manipulate it manually, use the loc_*() from
+automatically. To manipulate it manually, use the loc_``*``() from
error-report.h.
-7.2 Propagating errors
+Propagating errors
+------------------
An error can't always be reported to the user right where it's detected,
but often needs to be propagated up the call chain to a place that can
@@ -233,16 +275,17 @@ error, non-negative / -errno, non-null / null, or Error objects.
Example: when a function returns a non-null pointer on success, and it
can fail only in one way (as far as the caller is concerned), returning
null on failure is just fine, and certainly simpler and a lot easier on
-the eyes than propagating an Error object through an Error ** parameter.
+the eyes than propagating an Error object through an Error ``*````*`` parameter.
Example: when a function's callers need to report details on failure
-only the function really knows, use Error **, and set suitable errors.
+only the function really knows, use Error ``*````*``, and set suitable errors.
Do not report an error to the user when you're also returning an error
for somebody else to handle. Leave the reporting to the place that
consumes the error returned.
-7.3 Handling errors
+Handling errors
+---------------
Calling exit() is fine when handling configuration errors during
startup. It's problematic during normal operation. In particular,
diff --git a/README b/README.rst
similarity index 84%
rename from README
rename to README.rst
index 441c33eb2f..9ff2877416 100644
--- a/README
+++ b/README.rst
@@ -1,5 +1,6 @@
- QEMU README
- ===========
+===========
+QEMU README
+===========
QEMU is a generic and open source machine & userspace emulator and
virtualizer.
@@ -37,6 +38,9 @@ QEMU is multi-platform software intended to be buildable on all modern
Linux platforms, OS-X, Win32 (via the Mingw64 toolchain) and a variety
of other UNIX targets. The simple steps to build QEMU are:
+
+.. code-block:: shell
+
mkdir build
cd build
../configure
@@ -44,9 +48,9 @@ of other UNIX targets. The simple steps to build QEMU are:
Additional information can also be found online via the QEMU website:
- https://qemu.org/Hosts/Linux
- https://qemu.org/Hosts/Mac
- https://qemu.org/Hosts/W32
+* `<https://qemu.org/Hosts/Linux>`_
+* `<https://qemu.org/Hosts/Mac>`_
+* `<https://qemu.org/Hosts/W32>`_
Submitting patches
@@ -54,24 +58,29 @@ Submitting patches
The QEMU source code is maintained under the GIT version control system.
+.. code-block:: shell
+
git clone https://git.qemu.org/git/qemu.git
When submitting patches, one common approach is to use 'git
format-patch' and/or 'git send-email' to format & send the mail to the
qemu-devel@nongnu.org mailing list. All patches submitted must contain
a 'Signed-off-by' line from the author. Patches should follow the
-guidelines set out in the HACKING and CODING_STYLE files.
+guidelines set out in the HACKING.rst and CODING_STYLE.rst files.
Additional information on submitting patches can be found online via
the QEMU website
- https://qemu.org/Contribute/SubmitAPatch
- https://qemu.org/Contribute/TrivialPatches
+* `<https://qemu.org/Contribute/SubmitAPatch>`_
+* `<https://qemu.org/Contribute/TrivialPatches>`_
The QEMU website is also maintained under source control.
+.. code-block:: shell
+
git clone https://git.qemu.org/git/qemu-web.git
- https://www.qemu.org/2017/02/04/the-new-qemu-website-is-up/
+
+* `<https://www.qemu.org/2017/02/04/the-new-qemu-website-is-up/>`_
A 'git-publish' utility was created to make above process less
cumbersome, and is highly recommended for making regular contributions,
@@ -82,10 +91,12 @@ manually for once.
For installation instructions, please go to
- https://github.com/stefanha/git-publish
+* `<https://github.com/stefanha/git-publish>`_
The workflow with 'git-publish' is:
+.. code-block:: shell
+
$ git checkout master -b my-feature
$ # work on new commits, add your 'Signed-off-by' lines to each
$ git publish
@@ -95,6 +106,8 @@ back to it in the future.
Sending v2:
+.. code-block:: shell
+
$ git checkout my-feature # same topic branch
$ # making changes to the commits (using 'git rebase', for example)
$ git publish
@@ -109,7 +122,7 @@ The QEMU project uses Launchpad as its primary upstream bug tracker. Bugs
found when running code built from QEMU git or upstream released sources
should be reported via:
- https://bugs.launchpad.net/qemu/
+* `<https://bugs.launchpad.net/qemu/>`_
If using QEMU via an operating system vendor pre-built binary package, it
is preferable to report bugs to the vendor's own bug tracker first. If
@@ -118,7 +131,7 @@ reported via launchpad.
For additional information on bug reporting consult:
- https://qemu.org/Contribute/ReportABug
+* `<https://qemu.org/Contribute/ReportABug>`_
Contact
@@ -127,13 +140,11 @@ Contact
The QEMU community can be contacted in a number of ways, with the two
main methods being email and IRC
- - qemu-devel@nongnu.org
- https://lists.nongnu.org/mailman/listinfo/qemu-devel
- - #qemu on irc.oftc.net
+* `<mailto:qemu-devel@nongnu.org>`_
+* `<https://lists.nongnu.org/mailman/listinfo/qemu-devel>`_
+* #qemu on irc.oftc.net
Information on additional methods of contacting the community can be
found online via the QEMU website:
- https://qemu.org/Contribute/StartHere
-
--- End
+* `<https://qemu.org/Contribute/StartHere>`_
diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index d24c9441ee..aa9a354a0e 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -461,7 +461,7 @@ sub top_of_kernel_tree {
my @tree_check = (
"COPYING", "MAINTAINERS", "Makefile",
- "README", "docs", "VERSION",
+ "README.rst", "docs", "VERSION",
"vl.c"
);
--
2.21.0
^ permalink raw reply related [flat|nested] 9+ messages in thread* [Qemu-devel] [PULL 2/4] docs: merge HACKING.rst contents into CODING_STYLE.rst
2019-09-05 13:45 [Qemu-devel] [PULL 0/4] Docs patches Daniel P. Berrangé
2019-09-05 13:45 ` [Qemu-devel] [PULL 1/4] docs: convert README, CODING_STYLE and HACKING to RST syntax Daniel P. Berrangé
@ 2019-09-05 13:45 ` Daniel P. Berrangé
2019-09-05 13:45 ` [Qemu-devel] [PULL 3/4] docs: document use of automatic cleanup functions in glib Daniel P. Berrangé
` (3 subsequent siblings)
5 siblings, 0 replies; 9+ messages in thread
From: Daniel P. Berrangé @ 2019-09-05 13:45 UTC (permalink / raw)
To: qemu-devel
Cc: Peter Maydell, Daniel P. Berrangé,
Marc-André Lureau, Stefan Hajnoczi, Alex Bennée
The split of information between the two docs is rather arbitary and
unclear. It is simpler for contributors if all the information is in
one file.
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
---
CODING_STYLE.rst | 296 ++++++++++++++++++++++++++++++++++++++++++++++
HACKING.rst | 300 -----------------------------------------------
README.rst | 2 +-
3 files changed, 297 insertions(+), 301 deletions(-)
delete mode 100644 HACKING.rst
diff --git a/CODING_STYLE.rst b/CODING_STYLE.rst
index 713357cb80..4501d87352 100644
--- a/CODING_STYLE.rst
+++ b/CODING_STYLE.rst
@@ -205,6 +205,302 @@ comment anyway.)
Rationale: Consistency, and ease of visually picking out a multiline
comment from the surrounding code.
+Preprocessor
+============
+
+Variadic macros
+---------------
+
+For variadic macros, stick with this C99-like syntax:
+
+.. code-block:: c
+
+ #define DPRINTF(fmt, ...) \
+ do { printf("IRQ: " fmt, ## __VA_ARGS__); } while (0)
+
+Include directives
+------------------
+
+Order include directives as follows:
+
+.. code-block:: c
+
+ #include "qemu/osdep.h" /* Always first... */
+ #include <...> /* then system headers... */
+ #include "..." /* and finally QEMU headers. */
+
+The "qemu/osdep.h" header contains preprocessor macros that affect the behavior
+of core system headers like <stdint.h>. It must be the first include so that
+core system headers included by external libraries get the preprocessor macros
+that QEMU depends on.
+
+Do not include "qemu/osdep.h" from header files since the .c file will have
+already included it.
+
+C types
+=======
+
+It should be common sense to use the right type, but we have collected
+a few useful guidelines here.
+
+Scalars
+-------
+
+If you're using "int" or "long", odds are good that there's a better type.
+If a variable is counting something, it should be declared with an
+unsigned type.
+
+If it's host memory-size related, size_t should be a good choice (use
+ssize_t only if required). Guest RAM memory offsets must use ram_addr_t,
+but only for RAM, it may not cover whole guest address space.
+
+If it's file-size related, use off_t.
+If it's file-offset related (i.e., signed), use off_t.
+If it's just counting small numbers use "unsigned int";
+(on all but oddball embedded systems, you can assume that that
+type is at least four bytes wide).
+
+In the event that you require a specific width, use a standard type
+like int32_t, uint32_t, uint64_t, etc. The specific types are
+mandatory for VMState fields.
+
+Don't use Linux kernel internal types like u32, __u32 or __le32.
+
+Use hwaddr for guest physical addresses except pcibus_t
+for PCI addresses. In addition, ram_addr_t is a QEMU internal address
+space that maps guest RAM physical addresses into an intermediate
+address space that can map to host virtual address spaces. Generally
+speaking, the size of guest memory can always fit into ram_addr_t but
+it would not be correct to store an actual guest physical address in a
+ram_addr_t.
+
+For CPU virtual addresses there are several possible types.
+vaddr is the best type to use to hold a CPU virtual address in
+target-independent code. It is guaranteed to be large enough to hold a
+virtual address for any target, and it does not change size from target
+to target. It is always unsigned.
+target_ulong is a type the size of a virtual address on the CPU; this means
+it may be 32 or 64 bits depending on which target is being built. It should
+therefore be used only in target-specific code, and in some
+performance-critical built-per-target core code such as the TLB code.
+There is also a signed version, target_long.
+abi_ulong is for the ``*``-user targets, and represents a type the size of
+'void ``*``' in that target's ABI. (This may not be the same as the size of a
+full CPU virtual address in the case of target ABIs which use 32 bit pointers
+on 64 bit CPUs, like sparc32plus.) Definitions of structures that must match
+the target's ABI must use this type for anything that on the target is defined
+to be an 'unsigned long' or a pointer type.
+There is also a signed version, abi_long.
+
+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.
+
+Also, if you try to use e.g., "unsigned int" 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"
+and fixing all related variables would be too invasive.
+
+Finally, while using descriptive types is important, be careful not to
+go overboard. If whatever you're doing causes warnings, or requires
+casts, then reconsider or ask for help.
+
+Pointers
+--------
+
+Ensure that all of your pointers are "const-correct".
+Unless a pointer is used to modify the pointed-to storage,
+give it the "const" 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
+it points to, or it is aliased to another pointer that is.
+
+Typedefs
+--------
+
+Typedefs are used to eliminate the redundant 'struct' keyword, since type
+names have a different style than other identifiers ("CamelCase" versus
+"snake_case"). Each named struct type should have a CamelCase name and a
+corresponding typedef.
+
+Since certain C compilers choke on duplicated typedefs, you should avoid
+them and declare a typedef only in one header file. For common types,
+you can use "include/qemu/typedefs.h" for example. However, as a matter
+of convenience it is also perfectly fine to use forward struct
+definitions instead of typedefs in headers and function prototypes; this
+avoids problems with duplicated typedefs and reduces the need to include
+headers from other headers.
+
+Reserved namespaces in C and POSIX
+----------------------------------
+
+Underscore capital, double underscore, and underscore 't' suffixes should be
+avoided.
+
+Low level memory management
+===========================
+
+Use of the malloc/free/realloc/calloc/valloc/memalign/posix_memalign
+APIs is not allowed in the QEMU codebase. Instead of these routines,
+use the GLib memory allocation routines g_malloc/g_malloc0/g_new/
+g_new0/g_realloc/g_free or QEMU's qemu_memalign/qemu_blockalign/qemu_vfree
+APIs.
+
+Please note that g_malloc will exit on allocation failure, so there
+is no need to test for failure (as you would have to with malloc).
+Calling g_malloc with a zero size is valid and will return NULL.
+
+Prefer g_new(T, n) instead of g_malloc(sizeof(T) ``*`` n) for the following
+reasons:
+
+* It catches multiplication overflowing size_t;
+* It returns T ``*`` instead of void ``*``, letting compiler catch more type errors.
+
+Declarations like
+
+.. code-block:: c
+
+ T *v = g_malloc(sizeof(*v))
+
+are acceptable, though.
+
+Memory allocated by qemu_memalign or qemu_blockalign must be freed with
+qemu_vfree, since breaking this will cause problems on Win32.
+
+String manipulation
+===================
+
+Do not use the strncpy function. As mentioned in the man page, it does *not*
+guarantee a NULL-terminated buffer, which makes it extremely dangerous to use.
+It also zeros trailing destination bytes out to the specified length. Instead,
+use this similar function when possible, but note its different signature:
+
+.. code-block:: c
+
+ void pstrcpy(char *dest, int dest_buf_size, const char *src)
+
+Don't use strcat because it can't check for buffer overflows, but:
+
+.. code-block:: c
+
+ char *pstrcat(char *buf, int buf_size, const char *s)
+
+The same limitation exists with sprintf and vsprintf, so use snprintf and
+vsnprintf.
+
+QEMU provides other useful string functions:
+
+.. code-block:: c
+
+ int strstart(const char *str, const char *val, const char **ptr)
+ int stristart(const char *str, const char *val, const char **ptr)
+ int qemu_strnlen(const char *s, int max_len)
+
+There are also replacement character processing macros for isxyz and toxyz,
+so instead of e.g. isalnum you should use qemu_isalnum.
+
+Because of the memory management rules, you must use g_strdup/g_strndup
+instead of plain strdup/strndup.
+
+Printf-style functions
+======================
+
+Whenever you add a new printf-style function, i.e., one with a format
+string argument and following "..." in its prototype, be sure to use
+gcc's printf attribute directive in the prototype.
+
+This makes it so gcc's -Wformat and -Wformat-security options can do
+their jobs and cross-check format strings with the number and types
+of arguments.
+
+C standard, implementation defined and undefined behaviors
+==========================================================
+
+C code in QEMU should be written to the C99 language specification. A copy
+of the final version of the C99 standard with corrigenda TC1, TC2, and TC3
+included, formatted as a draft, can be downloaded from:
+
+ `<http://www.open-std.org/jtc1/sc22/WG14/www/docs/n1256.pdf>`_
+
+The C language specification defines regions of undefined behavior and
+implementation defined behavior (to give compiler authors enough leeway to
+produce better code). In general, code in QEMU should follow the language
+specification and avoid both undefined and implementation defined
+constructs. ("It works fine on the gcc I tested it with" is not a valid
+argument...) However there are a few areas where we allow ourselves to
+assume certain behaviors because in practice all the platforms we care about
+behave in the same way and writing strictly conformant code would be
+painful. These are:
+
+* you may assume that integers are 2s complement representation
+* you may assume that right shift of a signed integer duplicates
+ the sign bit (ie it is an arithmetic shift, not a logical shift)
+
+In addition, QEMU assumes that the compiler does not use the latitude
+given in C99 and C11 to treat aspects of signed '<<' as undefined, as
+documented in the GNU Compiler Collection manual starting at version 4.0.
+
+Error handling and reporting
+============================
+
+Reporting errors to the human user
+----------------------------------
+
+Do not use printf(), fprintf() or monitor_printf(). Instead, use
+error_report() or error_vreport() from error-report.h. This ensures the
+error is reported in the right place (current monitor or stderr), and in
+a uniform format.
+
+Use error_printf() & friends to print additional information.
+
+error_report() prints the current location. In certain common cases
+like command line parsing, the current location is tracked
+automatically. To manipulate it manually, use the loc_``*``() from
+error-report.h.
+
+Propagating errors
+------------------
+
+An error can't always be reported to the user right where it's detected,
+but often needs to be propagated up the call chain to a place that can
+handle it. This can be done in various ways.
+
+The most flexible one is Error objects. See error.h for usage
+information.
+
+Use the simplest suitable method to communicate success / failure to
+callers. Stick to common methods: non-negative on success / -1 on
+error, non-negative / -errno, non-null / null, or Error objects.
+
+Example: when a function returns a non-null pointer on success, and it
+can fail only in one way (as far as the caller is concerned), returning
+null on failure is just fine, and certainly simpler and a lot easier on
+the eyes than propagating an Error object through an Error ``*````*`` parameter.
+
+Example: when a function's callers need to report details on failure
+only the function really knows, use Error ``*````*``, and set suitable errors.
+
+Do not report an error to the user when you're also returning an error
+for somebody else to handle. Leave the reporting to the place that
+consumes the error returned.
+
+Handling errors
+---------------
+
+Calling exit() is fine when handling configuration errors during
+startup. It's problematic during normal operation. In particular,
+monitor commands should never exit().
+
+Do not call exit() or abort() to handle an error that can be triggered
+by the guest (e.g., some unimplemented corner case in guest code
+translation or device emulation). Guests should not be able to
+terminate QEMU.
+
+Note that &error_fatal is just another way to exit(1), and &error_abort
+is just another way to abort().
+
+
trace-events style
==================
diff --git a/HACKING.rst b/HACKING.rst
deleted file mode 100644
index 668fc420c3..0000000000
--- a/HACKING.rst
+++ /dev/null
@@ -1,300 +0,0 @@
-============
-QEMU Hacking
-============
-
-.. contents:: Table of Contents
-
-Preprocessor
-============
-
-Variadic macros
----------------
-
-For variadic macros, stick with this C99-like syntax:
-
-.. code-block:: c
-
- #define DPRINTF(fmt, ...) \
- do { printf("IRQ: " fmt, ## __VA_ARGS__); } while (0)
-
-Include directives
-------------------
-
-Order include directives as follows:
-
-.. code-block:: c
-
- #include "qemu/osdep.h" /* Always first... */
- #include <...> /* then system headers... */
- #include "..." /* and finally QEMU headers. */
-
-The "qemu/osdep.h" header contains preprocessor macros that affect the behavior
-of core system headers like <stdint.h>. It must be the first include so that
-core system headers included by external libraries get the preprocessor macros
-that QEMU depends on.
-
-Do not include "qemu/osdep.h" from header files since the .c file will have
-already included it.
-
-C types
-=======
-
-It should be common sense to use the right type, but we have collected
-a few useful guidelines here.
-
-Scalars
--------
-
-If you're using "int" or "long", odds are good that there's a better type.
-If a variable is counting something, it should be declared with an
-unsigned type.
-
-If it's host memory-size related, size_t should be a good choice (use
-ssize_t only if required). Guest RAM memory offsets must use ram_addr_t,
-but only for RAM, it may not cover whole guest address space.
-
-If it's file-size related, use off_t.
-If it's file-offset related (i.e., signed), use off_t.
-If it's just counting small numbers use "unsigned int";
-(on all but oddball embedded systems, you can assume that that
-type is at least four bytes wide).
-
-In the event that you require a specific width, use a standard type
-like int32_t, uint32_t, uint64_t, etc. The specific types are
-mandatory for VMState fields.
-
-Don't use Linux kernel internal types like u32, __u32 or __le32.
-
-Use hwaddr for guest physical addresses except pcibus_t
-for PCI addresses. In addition, ram_addr_t is a QEMU internal address
-space that maps guest RAM physical addresses into an intermediate
-address space that can map to host virtual address spaces. Generally
-speaking, the size of guest memory can always fit into ram_addr_t but
-it would not be correct to store an actual guest physical address in a
-ram_addr_t.
-
-For CPU virtual addresses there are several possible types.
-vaddr is the best type to use to hold a CPU virtual address in
-target-independent code. It is guaranteed to be large enough to hold a
-virtual address for any target, and it does not change size from target
-to target. It is always unsigned.
-target_ulong is a type the size of a virtual address on the CPU; this means
-it may be 32 or 64 bits depending on which target is being built. It should
-therefore be used only in target-specific code, and in some
-performance-critical built-per-target core code such as the TLB code.
-There is also a signed version, target_long.
-abi_ulong is for the ``*``-user targets, and represents a type the size of
-'void ``*``' in that target's ABI. (This may not be the same as the size of a
-full CPU virtual address in the case of target ABIs which use 32 bit pointers
-on 64 bit CPUs, like sparc32plus.) Definitions of structures that must match
-the target's ABI must use this type for anything that on the target is defined
-to be an 'unsigned long' or a pointer type.
-There is also a signed version, abi_long.
-
-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.
-
-Also, if you try to use e.g., "unsigned int" 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"
-and fixing all related variables would be too invasive.
-
-Finally, while using descriptive types is important, be careful not to
-go overboard. If whatever you're doing causes warnings, or requires
-casts, then reconsider or ask for help.
-
-Pointers
---------
-
-Ensure that all of your pointers are "const-correct".
-Unless a pointer is used to modify the pointed-to storage,
-give it the "const" 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
-it points to, or it is aliased to another pointer that is.
-
-Typedefs
---------
-
-Typedefs are used to eliminate the redundant 'struct' keyword, since type
-names have a different style than other identifiers ("CamelCase" versus
-"snake_case"). Each named struct type should have a CamelCase name and a
-corresponding typedef.
-
-Since certain C compilers choke on duplicated typedefs, you should avoid
-them and declare a typedef only in one header file. For common types,
-you can use "include/qemu/typedefs.h" for example. However, as a matter
-of convenience it is also perfectly fine to use forward struct
-definitions instead of typedefs in headers and function prototypes; this
-avoids problems with duplicated typedefs and reduces the need to include
-headers from other headers.
-
-Reserved namespaces in C and POSIX
-----------------------------------
-
-Underscore capital, double underscore, and underscore 't' suffixes should be
-avoided.
-
-Low level memory management
-===========================
-
-Use of the malloc/free/realloc/calloc/valloc/memalign/posix_memalign
-APIs is not allowed in the QEMU codebase. Instead of these routines,
-use the GLib memory allocation routines g_malloc/g_malloc0/g_new/
-g_new0/g_realloc/g_free or QEMU's qemu_memalign/qemu_blockalign/qemu_vfree
-APIs.
-
-Please note that g_malloc will exit on allocation failure, so there
-is no need to test for failure (as you would have to with malloc).
-Calling g_malloc with a zero size is valid and will return NULL.
-
-Prefer g_new(T, n) instead of g_malloc(sizeof(T) ``*`` n) for the following
-reasons:
-
-* It catches multiplication overflowing size_t;
-* It returns T ``*`` instead of void ``*``, letting compiler catch more type errors.
-
-Declarations like
-
-.. code-block:: c
-
- T *v = g_malloc(sizeof(*v))
-
-are acceptable, though.
-
-Memory allocated by qemu_memalign or qemu_blockalign must be freed with
-qemu_vfree, since breaking this will cause problems on Win32.
-
-String manipulation
-===================
-
-Do not use the strncpy function. As mentioned in the man page, it does *not*
-guarantee a NULL-terminated buffer, which makes it extremely dangerous to use.
-It also zeros trailing destination bytes out to the specified length. Instead,
-use this similar function when possible, but note its different signature:
-
-.. code-block:: c
-
- void pstrcpy(char *dest, int dest_buf_size, const char *src)
-
-Don't use strcat because it can't check for buffer overflows, but:
-
-.. code-block:: c
-
- char *pstrcat(char *buf, int buf_size, const char *s)
-
-The same limitation exists with sprintf and vsprintf, so use snprintf and
-vsnprintf.
-
-QEMU provides other useful string functions:
-
-.. code-block:: c
-
- int strstart(const char *str, const char *val, const char **ptr)
- int stristart(const char *str, const char *val, const char **ptr)
- int qemu_strnlen(const char *s, int max_len)
-
-There are also replacement character processing macros for isxyz and toxyz,
-so instead of e.g. isalnum you should use qemu_isalnum.
-
-Because of the memory management rules, you must use g_strdup/g_strndup
-instead of plain strdup/strndup.
-
-Printf-style functions
-======================
-
-Whenever you add a new printf-style function, i.e., one with a format
-string argument and following "..." in its prototype, be sure to use
-gcc's printf attribute directive in the prototype.
-
-This makes it so gcc's -Wformat and -Wformat-security options can do
-their jobs and cross-check format strings with the number and types
-of arguments.
-
-C standard, implementation defined and undefined behaviors
-==========================================================
-
-C code in QEMU should be written to the C99 language specification. A copy
-of the final version of the C99 standard with corrigenda TC1, TC2, and TC3
-included, formatted as a draft, can be downloaded from:
-
- `<http://www.open-std.org/jtc1/sc22/WG14/www/docs/n1256.pdf>`_
-
-The C language specification defines regions of undefined behavior and
-implementation defined behavior (to give compiler authors enough leeway to
-produce better code). In general, code in QEMU should follow the language
-specification and avoid both undefined and implementation defined
-constructs. ("It works fine on the gcc I tested it with" is not a valid
-argument...) However there are a few areas where we allow ourselves to
-assume certain behaviors because in practice all the platforms we care about
-behave in the same way and writing strictly conformant code would be
-painful. These are:
-
-* you may assume that integers are 2s complement representation
-* you may assume that right shift of a signed integer duplicates
- the sign bit (ie it is an arithmetic shift, not a logical shift)
-
-In addition, QEMU assumes that the compiler does not use the latitude
-given in C99 and C11 to treat aspects of signed '<<' as undefined, as
-documented in the GNU Compiler Collection manual starting at version 4.0.
-
-Error handling and reporting
-============================
-
-Reporting errors to the human user
-----------------------------------
-
-Do not use printf(), fprintf() or monitor_printf(). Instead, use
-error_report() or error_vreport() from error-report.h. This ensures the
-error is reported in the right place (current monitor or stderr), and in
-a uniform format.
-
-Use error_printf() & friends to print additional information.
-
-error_report() prints the current location. In certain common cases
-like command line parsing, the current location is tracked
-automatically. To manipulate it manually, use the loc_``*``() from
-error-report.h.
-
-Propagating errors
-------------------
-
-An error can't always be reported to the user right where it's detected,
-but often needs to be propagated up the call chain to a place that can
-handle it. This can be done in various ways.
-
-The most flexible one is Error objects. See error.h for usage
-information.
-
-Use the simplest suitable method to communicate success / failure to
-callers. Stick to common methods: non-negative on success / -1 on
-error, non-negative / -errno, non-null / null, or Error objects.
-
-Example: when a function returns a non-null pointer on success, and it
-can fail only in one way (as far as the caller is concerned), returning
-null on failure is just fine, and certainly simpler and a lot easier on
-the eyes than propagating an Error object through an Error ``*````*`` parameter.
-
-Example: when a function's callers need to report details on failure
-only the function really knows, use Error ``*````*``, and set suitable errors.
-
-Do not report an error to the user when you're also returning an error
-for somebody else to handle. Leave the reporting to the place that
-consumes the error returned.
-
-Handling errors
----------------
-
-Calling exit() is fine when handling configuration errors during
-startup. It's problematic during normal operation. In particular,
-monitor commands should never exit().
-
-Do not call exit() or abort() to handle an error that can be triggered
-by the guest (e.g., some unimplemented corner case in guest code
-translation or device emulation). Guests should not be able to
-terminate QEMU.
-
-Note that &error_fatal is just another way to exit(1), and &error_abort
-is just another way to abort().
diff --git a/README.rst b/README.rst
index 9ff2877416..7497709291 100644
--- a/README.rst
+++ b/README.rst
@@ -66,7 +66,7 @@ When submitting patches, one common approach is to use 'git
format-patch' and/or 'git send-email' to format & send the mail to the
qemu-devel@nongnu.org mailing list. All patches submitted must contain
a 'Signed-off-by' line from the author. Patches should follow the
-guidelines set out in the HACKING.rst and CODING_STYLE.rst files.
+guidelines set out in the CODING_STYLE.rst file.
Additional information on submitting patches can be found online via
the QEMU website
--
2.21.0
^ permalink raw reply related [flat|nested] 9+ messages in thread* [Qemu-devel] [PULL 3/4] docs: document use of automatic cleanup functions in glib
2019-09-05 13:45 [Qemu-devel] [PULL 0/4] Docs patches Daniel P. Berrangé
2019-09-05 13:45 ` [Qemu-devel] [PULL 1/4] docs: convert README, CODING_STYLE and HACKING to RST syntax Daniel P. Berrangé
2019-09-05 13:45 ` [Qemu-devel] [PULL 2/4] docs: merge HACKING.rst contents into CODING_STYLE.rst Daniel P. Berrangé
@ 2019-09-05 13:45 ` Daniel P. Berrangé
2019-09-05 13:45 ` [Qemu-devel] [PULL 4/4] docs: split the CODING_STYLE doc into distinct groups Daniel P. Berrangé
` (2 subsequent siblings)
5 siblings, 0 replies; 9+ messages in thread
From: Daniel P. Berrangé @ 2019-09-05 13:45 UTC (permalink / raw)
To: qemu-devel
Cc: Peter Maydell, Daniel P. Berrangé,
Marc-André Lureau, Stefan Hajnoczi, Alex Bennée
Document the use of g_autofree and g_autoptr in glib for automatic
freeing of memory.
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
---
CODING_STYLE.rst | 85 ++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 85 insertions(+)
diff --git a/CODING_STYLE.rst b/CODING_STYLE.rst
index 4501d87352..39397f0f6f 100644
--- a/CODING_STYLE.rst
+++ b/CODING_STYLE.rst
@@ -441,6 +441,91 @@ In addition, QEMU assumes that the compiler does not use the latitude
given in C99 and C11 to treat aspects of signed '<<' as undefined, as
documented in the GNU Compiler Collection manual starting at version 4.0.
+Automatic memory deallocation
+=============================
+
+QEMU has a mandatory dependency either the GCC or CLang compiler. As
+such it has the freedom to make use of a C language extension for
+automatically running a cleanup function when a stack variable goes
+out of scope. This can be used to simplify function cleanup paths,
+often allowing many goto jumps to be eliminated, through automatic
+free'ing of memory.
+
+The GLib2 library provides a number of functions/macros for enabling
+automatic cleanup:
+
+ `<https://developer.gnome.org/glib/stable/glib-Miscellaneous-Macros.html>`_
+
+Most notably:
+
+* g_autofree - will invoke g_free() on the variable going out of scope
+
+* g_autoptr - for structs / objects, will invoke the cleanup func created
+ by a previous use of G_DEFINE_AUTOPTR_CLEANUP_FUNC. This is
+ supported for most GLib data types and GObjects
+
+For example, instead of
+
+.. code-block:: c
+
+ int somefunc(void) {
+ int ret = -1;
+ char *foo = g_strdup_printf("foo%", "wibble");
+ GList *bar = .....
+
+ if (eek) {
+ goto cleanup;
+ }
+
+ ret = 0;
+
+ cleanup:
+ g_free(foo);
+ g_list_free(bar);
+ return ret;
+ }
+
+Using g_autofree/g_autoptr enables the code to be written as:
+
+.. code-block:: c
+
+ int somefunc(void) {
+ g_autofree char *foo = g_strdup_printf("foo%", "wibble");
+ g_autoptr (GList) bar = .....
+
+ if (eek) {
+ return -1;
+ }
+
+ return 0;
+ }
+
+While this generally results in simpler, less leak-prone code, there
+are still some caveats to beware of
+
+* Variables declared with g_auto* MUST always be initialized,
+ otherwise the cleanup function will use uninitialized stack memory
+
+* If a variable declared with g_auto* holds a value which must
+ live beyond the life of the function, that value must be saved
+ and the original variable NULL'd out. This can be simpler using
+ g_steal_pointer
+
+
+.. code-block:: c
+
+ char *somefunc(void) {
+ g_autofree char *foo = g_strdup_printf("foo%", "wibble");
+ g_autoptr (GList) bar = .....
+
+ if (eek) {
+ return NULL;
+ }
+
+ return g_steal_pointer(&foo);
+ }
+
+
Error handling and reporting
============================
--
2.21.0
^ permalink raw reply related [flat|nested] 9+ messages in thread* [Qemu-devel] [PULL 4/4] docs: split the CODING_STYLE doc into distinct groups
2019-09-05 13:45 [Qemu-devel] [PULL 0/4] Docs patches Daniel P. Berrangé
` (2 preceding siblings ...)
2019-09-05 13:45 ` [Qemu-devel] [PULL 3/4] docs: document use of automatic cleanup functions in glib Daniel P. Berrangé
@ 2019-09-05 13:45 ` Daniel P. Berrangé
2019-09-05 15:34 ` [Qemu-devel] [PULL 0/4] Docs patches Peter Maydell
2019-09-05 16:08 ` Peter Maydell
5 siblings, 0 replies; 9+ messages in thread
From: Daniel P. Berrangé @ 2019-09-05 13:45 UTC (permalink / raw)
To: qemu-devel
Cc: Peter Maydell, Daniel P. Berrangé,
Marc-André Lureau, Stefan Hajnoczi, Alex Bennée
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
---
CODING_STYLE.rst | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/CODING_STYLE.rst b/CODING_STYLE.rst
index 39397f0f6f..427699e0e4 100644
--- a/CODING_STYLE.rst
+++ b/CODING_STYLE.rst
@@ -7,6 +7,9 @@ QEMU Coding Style
Please use the script checkpatch.pl in the scripts directory to check
patches before submitting.
+Formatting and style
+********************
+
Whitespace
==========
@@ -205,6 +208,9 @@ comment anyway.)
Rationale: Consistency, and ease of visually picking out a multiline
comment from the surrounding code.
+Language usage
+**************
+
Preprocessor
============
@@ -526,6 +532,9 @@ are still some caveats to beware of
}
+QEMU Specific Idioms
+********************
+
Error handling and reporting
============================
--
2.21.0
^ permalink raw reply related [flat|nested] 9+ messages in thread* Re: [Qemu-devel] [PULL 0/4] Docs patches
2019-09-05 13:45 [Qemu-devel] [PULL 0/4] Docs patches Daniel P. Berrangé
` (3 preceding siblings ...)
2019-09-05 13:45 ` [Qemu-devel] [PULL 4/4] docs: split the CODING_STYLE doc into distinct groups Daniel P. Berrangé
@ 2019-09-05 15:34 ` Peter Maydell
2019-09-06 9:24 ` Daniel P. Berrangé
2019-09-05 16:08 ` Peter Maydell
5 siblings, 1 reply; 9+ messages in thread
From: Peter Maydell @ 2019-09-05 15:34 UTC (permalink / raw)
To: Daniel P. Berrangé
Cc: Marc-André Lureau, Alex Bennée, QEMU Developers,
Stefan Hajnoczi
On Thu, 5 Sep 2019 at 14:45, Daniel P. Berrangé <berrange@redhat.com> wrote:
>
> The following changes since commit 500efcfcf0fe2e0dae1d25637a13435ce7b6e421:
>
> Merge remote-tracking branch 'remotes/rth/tags/pull-or1k-20190904' into staging (2019-09-05 09:33:01 +0100)
>
> are available in the Git repository at:
>
> https://github.com/berrange/qemu tags/docs-pull-request
>
> for you to fetch changes up to 9f8efa74d3f1cb9ceeee957ee382c2b4feb2ae30:
>
> docs: split the CODING_STYLE doc into distinct groups (2019-09-05 14:41:00 +0100)
>
> ----------------------------------------------------------------
>
> * Merges HACKING into CODING_STYLE
> * Converts README and CODING_STYLE docs into RST syntax
> * Documents use of auto cleanup functions
>
> ----------------------------------------------------------------
>
> Daniel P. Berrangé (4):
> docs: convert README, CODING_STYLE and HACKING to RST syntax
> docs: merge HACKING.rst contents into CODING_STYLE.rst
> docs: document use of automatic cleanup functions in glib
> docs: split the CODING_STYLE doc into distinct groups
>
> CODING_STYLE | 216 --------------
> CODING_STYLE.rst | 641 ++++++++++++++++++++++++++++++++++++++++++
> HACKING | 257 -----------------
> README => README.rst | 47 ++--
> scripts/checkpatch.pl | 2 +-
I'm going to apply this, but something I thought of looking at
the diffstat: should some or all of this be in the docs/devel
manual rather than free-floating rst files in the root directory?
thanks
-- PMM
^ permalink raw reply [flat|nested] 9+ messages in thread* Re: [Qemu-devel] [PULL 0/4] Docs patches
2019-09-05 15:34 ` [Qemu-devel] [PULL 0/4] Docs patches Peter Maydell
@ 2019-09-06 9:24 ` Daniel P. Berrangé
2019-09-06 13:13 ` Eric Blake
0 siblings, 1 reply; 9+ messages in thread
From: Daniel P. Berrangé @ 2019-09-06 9:24 UTC (permalink / raw)
To: Peter Maydell
Cc: Alex Bennée, Marc-André Lureau, QEMU Developers,
Stefan Hajnoczi
On Thu, Sep 05, 2019 at 04:34:33PM +0100, Peter Maydell wrote:
> On Thu, 5 Sep 2019 at 14:45, Daniel P. Berrangé <berrange@redhat.com> wrote:
> >
> > The following changes since commit 500efcfcf0fe2e0dae1d25637a13435ce7b6e421:
> >
> > Merge remote-tracking branch 'remotes/rth/tags/pull-or1k-20190904' into staging (2019-09-05 09:33:01 +0100)
> >
> > are available in the Git repository at:
> >
> > https://github.com/berrange/qemu tags/docs-pull-request
> >
> > for you to fetch changes up to 9f8efa74d3f1cb9ceeee957ee382c2b4feb2ae30:
> >
> > docs: split the CODING_STYLE doc into distinct groups (2019-09-05 14:41:00 +0100)
> >
> > ----------------------------------------------------------------
> >
> > * Merges HACKING into CODING_STYLE
> > * Converts README and CODING_STYLE docs into RST syntax
> > * Documents use of auto cleanup functions
> >
> > ----------------------------------------------------------------
> >
> > Daniel P. Berrangé (4):
> > docs: convert README, CODING_STYLE and HACKING to RST syntax
> > docs: merge HACKING.rst contents into CODING_STYLE.rst
> > docs: document use of automatic cleanup functions in glib
> > docs: split the CODING_STYLE doc into distinct groups
> >
> > CODING_STYLE | 216 --------------
> > CODING_STYLE.rst | 641 ++++++++++++++++++++++++++++++++++++++++++
> > HACKING | 257 -----------------
> > README => README.rst | 47 ++--
> > scripts/checkpatch.pl | 2 +-
>
> I'm going to apply this, but something I thought of looking at
> the diffstat: should some or all of this be in the docs/devel
> manual rather than free-floating rst files in the root directory?
The answer really hinges on whether moving CODING_STYLE into the
docs/devel directory will make it less obvious to users.
On a related point, with the prevelance of github/gitlab for
hosting, it has become fairly common to have a top level
CONTRIBUTING.md file, with guidance of key factors relating
to contributing - how to submit patches, code of conduct,
developer signoff, coding style, etc. This file doesn't
have to contain the actual content - often people just use
it as an index to link to all the individual topic docs:
https://github.com/rails/rails/blob/master/CONTRIBUTING.md
https://github.com/atom/atom/blob/master/CONTRIBUTING.md
https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md
https://github.com/creativecommons/.github/blob/master/CONTRIBUTING.md
So we could just move CODING_STYLE into the docs/devel dir and link
to it from a CONTRIBUTING.md (well .rst) file.
Regards,
Daniel
--
|: https://berrange.com -o- https://www.flickr.com/photos/dberrange :|
|: https://libvirt.org -o- https://fstop138.berrange.com :|
|: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|
^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [Qemu-devel] [PULL 0/4] Docs patches
2019-09-06 9:24 ` Daniel P. Berrangé
@ 2019-09-06 13:13 ` Eric Blake
0 siblings, 0 replies; 9+ messages in thread
From: Eric Blake @ 2019-09-06 13:13 UTC (permalink / raw)
To: Daniel P. Berrangé, Peter Maydell
Cc: Marc-André Lureau, Alex Bennée, QEMU Developers,
Stefan Hajnoczi
[-- Attachment #1.1: Type: text/plain, Size: 1166 bytes --]
On 9/6/19 4:24 AM, Daniel P. Berrangé wrote:
>>
>> I'm going to apply this, but something I thought of looking at
>> the diffstat: should some or all of this be in the docs/devel
>> manual rather than free-floating rst files in the root directory?
>
> The answer really hinges on whether moving CODING_STYLE into the
> docs/devel directory will make it less obvious to users.
A git symlink would allow us to keep the file at the top level (for easy
location while browsing the repository) as well as under docs (for easy
incorporation into the doc build recipes). I don't know if tooling
would require the original in one place (forcing the other to be the
link), or if you can do it in either direction.
>
> So we could just move CODING_STYLE into the docs/devel dir and link
> to it from a CONTRIBUTING.md (well .rst) file.
A textual link in an actual file is slightly different than a git
symlink, but yes, that would probably also work (even if it requires
chasing through one more layer of files).
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3226
Virtualization: qemu.org | libvirt.org
[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 488 bytes --]
^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [Qemu-devel] [PULL 0/4] Docs patches
2019-09-05 13:45 [Qemu-devel] [PULL 0/4] Docs patches Daniel P. Berrangé
` (4 preceding siblings ...)
2019-09-05 15:34 ` [Qemu-devel] [PULL 0/4] Docs patches Peter Maydell
@ 2019-09-05 16:08 ` Peter Maydell
5 siblings, 0 replies; 9+ messages in thread
From: Peter Maydell @ 2019-09-05 16:08 UTC (permalink / raw)
To: Daniel P. Berrangé
Cc: Marc-André Lureau, Alex Bennée, QEMU Developers,
Stefan Hajnoczi
On Thu, 5 Sep 2019 at 14:45, Daniel P. Berrangé <berrange@redhat.com> wrote:
>
> The following changes since commit 500efcfcf0fe2e0dae1d25637a13435ce7b6e421:
>
> Merge remote-tracking branch 'remotes/rth/tags/pull-or1k-20190904' into staging (2019-09-05 09:33:01 +0100)
>
> are available in the Git repository at:
>
> https://github.com/berrange/qemu tags/docs-pull-request
>
> for you to fetch changes up to 9f8efa74d3f1cb9ceeee957ee382c2b4feb2ae30:
>
> docs: split the CODING_STYLE doc into distinct groups (2019-09-05 14:41:00 +0100)
>
> ----------------------------------------------------------------
>
> * Merges HACKING into CODING_STYLE
> * Converts README and CODING_STYLE docs into RST syntax
> * Documents use of auto cleanup functions
>
> ----------------------------------------------------------------
Applied, thanks.
Please update the changelog at https://wiki.qemu.org/ChangeLog/4.2
for any user-visible changes.
-- PMM
^ permalink raw reply [flat|nested] 9+ messages in thread