mirror of https://github.com/xemu-project/xemu.git
docs: add docs about use of automatic cleanup functions
This is ostensibly about adding docs for the g_autofree/g_autoptr macros. As part of doing that, however, the existing HACKING doc is merged into the CODING_STYLE doc and the text is converted to rst with a table of contents. -----BEGIN PGP SIGNATURE----- iQIzBAABCAAdFiEE2vOm/bJrYpEtDo4/vobrtBUQT98FAl1xERAACgkQvobrtBUQ T99qmA/+MjsM0xjuc1qCd3JigEz6wJTiy2li/KLbSPcnKlcPVCJYjqAzxGtT4Hqk a8QTTgzdE7+Exto98mBfALZEUgt+k/354OsHMtKrN8u9b4c7WaQV4C/MndmvD29O 3DX7wdDQuL8flC2GhXlk1x5x8vnD5S7xxWThx2PmmOS4qkFJNFuIf8l9LtNUybkU tVSKJ0t9oICdfCa3tMfJ/0Sak5Vlrl0WB+iBGSxUtpsZC6Hjbk7ny1iwfsIsQ4GN hsLkV2RYU8jb3576JujwLTySixO1vL5eDaggAegDm3pA1ESa/pTP3CTQXuRneJ1b Ko+X69LYPV1bj+SpxdJeXj5Ipi6O/6Cw4onNUoHZWWSFZ0tsqXzMq/iuShuXjUoO Xy5IwY3k5p31YT3I6jYtlUZ0GI1WAE8IYjRZM8tMrmmQVI2xELGG2tHZlr28i9/c cWSSd5KF5t5JOAJXkzRRUVujwdvYfTE6/gwDlmN5CZ9umS6ieBa/Hx5qWFaasZnk +g1OuG2LuTtwN/kyw+mkDTHvZ/pYWDRJ+3uK2xq8TtTZXJidp/ZVWOF78qPHScXw zsHCRqS9m/6TK2tl8tpB7PZW1DfwaTlP3iz7DRHGCLa80+DdZ+gkjISBmCX+LEqh n0Og4z2Wlu95WdJCBUFEuTKvaM04QYhLanLFPAeI4akJmiteHbw= =8csv -----END PGP SIGNATURE----- Merge remote-tracking branch 'remotes/berrange/tags/docs-pull-request' into staging docs: add docs about use of automatic cleanup functions This is ostensibly about adding docs for the g_autofree/g_autoptr macros. As part of doing that, however, the existing HACKING doc is merged into the CODING_STYLE doc and the text is converted to rst with a table of contents. # gpg: Signature made Thu 05 Sep 2019 14:43:44 BST # gpg: using RSA key DAF3A6FDB26B62912D0E8E3FBE86EBB415104FDF # gpg: Good signature from "Daniel P. Berrange <dan@berrange.com>" [full] # gpg: aka "Daniel P. Berrange <berrange@redhat.com>" [full] # Primary key fingerprint: DAF3 A6FD B26B 6291 2D0E 8E3F BE86 EBB4 1510 4FDF * remotes/berrange/tags/docs-pull-request: docs: split the CODING_STYLE doc into distinct groups docs: document use of automatic cleanup functions in glib docs: merge HACKING.rst contents into CODING_STYLE.rst docs: convert README, CODING_STYLE and HACKING to RST syntax Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
This commit is contained in:
commit
74aa913fe6
216
CODING_STYLE
216
CODING_STYLE
|
@ -1,216 +0,0 @@
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||||||
QEMU Coding Style
|
|
||||||
=================
|
|
||||||
|
|
||||||
Please use the script checkpatch.pl in the scripts directory to check
|
|
||||||
patches before submitting.
|
|
||||||
|
|
||||||
1. 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
|
|
||||||
can tell the difference between a tab and eight spaces from a distance
|
|
||||||
of approximately fifteen parsecs. Many a flamewar has been fought and
|
|
||||||
lost on this issue.
|
|
||||||
|
|
||||||
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.
|
|
||||||
|
|
||||||
Do not leave whitespace dangling off the ends of lines.
|
|
||||||
|
|
||||||
1.1 Multiline Indent
|
|
||||||
|
|
||||||
There are several places where indent is necessary:
|
|
||||||
|
|
||||||
- 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.
|
|
||||||
|
|
||||||
In case of if/else, while/for, align the secondary lines just after the
|
|
||||||
opening parenthesis of the first.
|
|
||||||
|
|
||||||
For example:
|
|
||||||
|
|
||||||
if (a == 1 &&
|
|
||||||
b == 2) {
|
|
||||||
|
|
||||||
while (a == 1 &&
|
|
||||||
b == 2) {
|
|
||||||
|
|
||||||
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
|
|
||||||
|
|
||||||
For example:
|
|
||||||
|
|
||||||
do_something(x, y,
|
|
||||||
z);
|
|
||||||
|
|
||||||
do_something(x, y,
|
|
||||||
z);
|
|
||||||
|
|
||||||
do_something(x, do_another(y,
|
|
||||||
z));
|
|
||||||
|
|
||||||
2. Line width
|
|
||||||
|
|
||||||
Lines should be 80 characters; try not to make them longer.
|
|
||||||
|
|
||||||
Sometimes it is hard to do, especially when dealing with QEMU subsystems
|
|
||||||
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
|
|
||||||
|
|
||||||
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
|
|
||||||
names and function type names should also be in CamelCase. Scalar type
|
|
||||||
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
|
|
||||||
readers that they are seeing a wrapped version; otherwise avoid this prefix.
|
|
||||||
|
|
||||||
4. 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
|
|
||||||
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:
|
|
||||||
|
|
||||||
if (a == 5) {
|
|
||||||
printf("a was 5.\n");
|
|
||||||
} else if (a == 6) {
|
|
||||||
printf("a was 6.\n");
|
|
||||||
} else {
|
|
||||||
printf("a was something else entirely.\n");
|
|
||||||
}
|
|
||||||
|
|
||||||
Note that 'else if' is considered a single statement; otherwise a long if/
|
|
||||||
else if/else if/.../else sequence would need an indent for every else
|
|
||||||
statement.
|
|
||||||
|
|
||||||
An exception is the opening brace for a function; for reasons of tradition
|
|
||||||
and clarity it comes on a line by itself:
|
|
||||||
|
|
||||||
void a_function(void)
|
|
||||||
{
|
|
||||||
do_something();
|
|
||||||
}
|
|
||||||
|
|
||||||
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
|
|
||||||
|
|
||||||
Mixed declarations (interleaving statements and declarations within
|
|
||||||
blocks) are generally not allowed; declarations should be at the beginning
|
|
||||||
of blocks.
|
|
||||||
|
|
||||||
Every now and then, an exception is made for declarations inside a
|
|
||||||
#ifdef or #ifndef block: if the code looks nicer, such declarations can
|
|
||||||
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
|
|
||||||
|
|
||||||
When comparing a variable for (in)equality with a constant, list the
|
|
||||||
constant on the right, as in:
|
|
||||||
|
|
||||||
if (a == 1) {
|
|
||||||
/* Reads like: "If a equals 1" */
|
|
||||||
do_something();
|
|
||||||
}
|
|
||||||
|
|
||||||
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
|
|
||||||
|
|
||||||
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:
|
|
||||||
/*
|
|
||||||
* 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
|
|
||||||
Standards form which does not have stars on the left, or other
|
|
||||||
variations; avoid these when writing new comments, but don't worry
|
|
||||||
about converting to the preferred form unless you're editing that
|
|
||||||
comment anyway.)
|
|
||||||
|
|
||||||
Rationale: Consistency, and ease of visually picking out a multiline
|
|
||||||
comment from the surrounding code.
|
|
||||||
|
|
||||||
8. trace-events style
|
|
||||||
|
|
||||||
8.1 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
|
|
||||||
|
|
||||||
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"
|
|
||||||
|
|
||||||
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"
|
|
||||||
|
|
||||||
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
|
|
||||||
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
|
|
||||||
|
|
||||||
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
|
|
|
@ -0,0 +1,641 @@
|
||||||
|
=================
|
||||||
|
QEMU Coding Style
|
||||||
|
=================
|
||||||
|
|
||||||
|
.. contents:: Table of Contents
|
||||||
|
|
||||||
|
Please use the script checkpatch.pl in the scripts directory to check
|
||||||
|
patches before submitting.
|
||||||
|
|
||||||
|
Formatting and style
|
||||||
|
********************
|
||||||
|
|
||||||
|
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
|
||||||
|
can tell the difference between a tab and eight spaces from a distance
|
||||||
|
of approximately fifteen parsecs. Many a flamewar has been fought and
|
||||||
|
lost on this issue.
|
||||||
|
|
||||||
|
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.
|
||||||
|
|
||||||
|
Do not leave whitespace dangling off the ends of lines.
|
||||||
|
|
||||||
|
Multiline Indent
|
||||||
|
----------------
|
||||||
|
|
||||||
|
There are several places where indent is necessary:
|
||||||
|
|
||||||
|
* 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.
|
||||||
|
|
||||||
|
In case of if/else, while/for, align the secondary lines just after the
|
||||||
|
opening parenthesis of the first.
|
||||||
|
|
||||||
|
For example:
|
||||||
|
|
||||||
|
.. code-block:: c
|
||||||
|
|
||||||
|
if (a == 1 &&
|
||||||
|
b == 2) {
|
||||||
|
|
||||||
|
while (a == 1 &&
|
||||||
|
b == 2) {
|
||||||
|
|
||||||
|
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
|
||||||
|
|
||||||
|
For example:
|
||||||
|
|
||||||
|
.. code-block:: c
|
||||||
|
|
||||||
|
do_something(x, y,
|
||||||
|
z);
|
||||||
|
|
||||||
|
do_something(x, y,
|
||||||
|
z);
|
||||||
|
|
||||||
|
do_something(x, do_another(y,
|
||||||
|
z));
|
||||||
|
|
||||||
|
Line width
|
||||||
|
==========
|
||||||
|
|
||||||
|
Lines should be 80 characters; try not to make them longer.
|
||||||
|
|
||||||
|
Sometimes it is hard to do, especially when dealing with QEMU subsystems
|
||||||
|
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.
|
||||||
|
|
||||||
|
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
|
||||||
|
names and function type names should also be in CamelCase. Scalar type
|
||||||
|
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
|
||||||
|
readers that they are seeing a wrapped version; otherwise avoid this prefix.
|
||||||
|
|
||||||
|
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
|
||||||
|
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) {
|
||||||
|
printf("a was 6.\n");
|
||||||
|
} else {
|
||||||
|
printf("a was something else entirely.\n");
|
||||||
|
}
|
||||||
|
|
||||||
|
Note that 'else if' is considered a single statement; otherwise a long if/
|
||||||
|
else if/else if/.../else sequence would need an indent for every else
|
||||||
|
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();
|
||||||
|
}
|
||||||
|
|
||||||
|
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.
|
||||||
|
|
||||||
|
Declarations
|
||||||
|
============
|
||||||
|
|
||||||
|
Mixed declarations (interleaving statements and declarations within
|
||||||
|
blocks) are generally not allowed; declarations should be at the beginning
|
||||||
|
of blocks.
|
||||||
|
|
||||||
|
Every now and then, an exception is made for declarations inside a
|
||||||
|
#ifdef or #ifndef block: if the code looks nicer, such declarations can
|
||||||
|
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.
|
||||||
|
|
||||||
|
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();
|
||||||
|
}
|
||||||
|
|
||||||
|
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.
|
||||||
|
|
||||||
|
Comment style
|
||||||
|
=============
|
||||||
|
|
||||||
|
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:
|
||||||
|
|
||||||
|
.. 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
|
||||||
|
Standards form which does not have stars on the left, or other
|
||||||
|
variations; avoid these when writing new comments, but don't worry
|
||||||
|
about converting to the preferred form unless you're editing that
|
||||||
|
comment anyway.)
|
||||||
|
|
||||||
|
Rationale: Consistency, and ease of visually picking out a multiline
|
||||||
|
comment from the surrounding code.
|
||||||
|
|
||||||
|
Language usage
|
||||||
|
**************
|
||||||
|
|
||||||
|
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.
|
||||||
|
|
||||||
|
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);
|
||||||
|
}
|
||||||
|
|
||||||
|
|
||||||
|
QEMU Specific Idioms
|
||||||
|
********************
|
||||||
|
|
||||||
|
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
|
||||||
|
==================
|
||||||
|
|
||||||
|
0x prefix
|
||||||
|
---------
|
||||||
|
|
||||||
|
In trace-events files, use a '0x' prefix to specify hex numbers, as in:
|
||||||
|
|
||||||
|
.. 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):
|
||||||
|
|
||||||
|
.. 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.:
|
||||||
|
|
||||||
|
.. 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
|
||||||
|
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.
|
||||||
|
|
||||||
|
'#' 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
|
257
HACKING
257
HACKING
|
@ -1,257 +0,0 @@
|
||||||
1. Preprocessor
|
|
||||||
|
|
||||||
1.1. Variadic macros
|
|
||||||
|
|
||||||
For variadic macros, stick with this C99-like syntax:
|
|
||||||
|
|
||||||
#define DPRINTF(fmt, ...) \
|
|
||||||
do { printf("IRQ: " fmt, ## __VA_ARGS__); } while (0)
|
|
||||||
|
|
||||||
1.2. Include directives
|
|
||||||
|
|
||||||
Order include directives as follows:
|
|
||||||
|
|
||||||
#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.
|
|
||||||
|
|
||||||
2. C types
|
|
||||||
|
|
||||||
It should be common sense to use the right type, but we have collected
|
|
||||||
a few useful guidelines here.
|
|
||||||
|
|
||||||
2.1. 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.
|
|
||||||
|
|
||||||
2.2. 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.
|
|
||||||
|
|
||||||
2.3. 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.
|
|
||||||
|
|
||||||
2.4. Reserved namespaces in C and POSIX
|
|
||||||
Underscore capital, double underscore, and underscore 't' suffixes should be
|
|
||||||
avoided.
|
|
||||||
|
|
||||||
3. 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:
|
|
||||||
|
|
||||||
a. It catches multiplication overflowing size_t;
|
|
||||||
b. It returns T * instead of void *, letting compiler catch more type
|
|
||||||
errors.
|
|
||||||
|
|
||||||
Declarations like 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.
|
|
||||||
|
|
||||||
4. 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)
|
|
||||||
|
|
||||||
Don't use strcat because it can't check for buffer overflows, but:
|
|
||||||
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)
|
|
||||||
|
|
||||||
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.
|
|
||||||
|
|
||||||
5. 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.
|
|
||||||
|
|
||||||
6. 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.
|
|
||||||
|
|
||||||
7. Error handling and reporting
|
|
||||||
|
|
||||||
7.1 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.
|
|
||||||
|
|
||||||
7.2 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.
|
|
||||||
|
|
||||||
7.3 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().
|
|
|
@ -1,5 +1,6 @@
|
||||||
QEMU README
|
===========
|
||||||
===========
|
QEMU README
|
||||||
|
===========
|
||||||
|
|
||||||
QEMU is a generic and open source machine & userspace emulator and
|
QEMU is a generic and open source machine & userspace emulator and
|
||||||
virtualizer.
|
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
|
Linux platforms, OS-X, Win32 (via the Mingw64 toolchain) and a variety
|
||||||
of other UNIX targets. The simple steps to build QEMU are:
|
of other UNIX targets. The simple steps to build QEMU are:
|
||||||
|
|
||||||
|
|
||||||
|
.. code-block:: shell
|
||||||
|
|
||||||
mkdir build
|
mkdir build
|
||||||
cd build
|
cd build
|
||||||
../configure
|
../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:
|
Additional information can also be found online via the QEMU website:
|
||||||
|
|
||||||
https://qemu.org/Hosts/Linux
|
* `<https://qemu.org/Hosts/Linux>`_
|
||||||
https://qemu.org/Hosts/Mac
|
* `<https://qemu.org/Hosts/Mac>`_
|
||||||
https://qemu.org/Hosts/W32
|
* `<https://qemu.org/Hosts/W32>`_
|
||||||
|
|
||||||
|
|
||||||
Submitting patches
|
Submitting patches
|
||||||
|
@ -54,24 +58,29 @@ Submitting patches
|
||||||
|
|
||||||
The QEMU source code is maintained under the GIT version control system.
|
The QEMU source code is maintained under the GIT version control system.
|
||||||
|
|
||||||
|
.. code-block:: shell
|
||||||
|
|
||||||
git clone https://git.qemu.org/git/qemu.git
|
git clone https://git.qemu.org/git/qemu.git
|
||||||
|
|
||||||
When submitting patches, one common approach is to use '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
|
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
|
qemu-devel@nongnu.org mailing list. All patches submitted must contain
|
||||||
a 'Signed-off-by' line from the author. Patches should follow the
|
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 CODING_STYLE.rst file.
|
||||||
|
|
||||||
Additional information on submitting patches can be found online via
|
Additional information on submitting patches can be found online via
|
||||||
the QEMU website
|
the QEMU website
|
||||||
|
|
||||||
https://qemu.org/Contribute/SubmitAPatch
|
* `<https://qemu.org/Contribute/SubmitAPatch>`_
|
||||||
https://qemu.org/Contribute/TrivialPatches
|
* `<https://qemu.org/Contribute/TrivialPatches>`_
|
||||||
|
|
||||||
The QEMU website is also maintained under source control.
|
The QEMU website is also maintained under source control.
|
||||||
|
|
||||||
|
.. code-block:: shell
|
||||||
|
|
||||||
git clone https://git.qemu.org/git/qemu-web.git
|
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
|
A 'git-publish' utility was created to make above process less
|
||||||
cumbersome, and is highly recommended for making regular contributions,
|
cumbersome, and is highly recommended for making regular contributions,
|
||||||
|
@ -82,10 +91,12 @@ manually for once.
|
||||||
|
|
||||||
For installation instructions, please go to
|
For installation instructions, please go to
|
||||||
|
|
||||||
https://github.com/stefanha/git-publish
|
* `<https://github.com/stefanha/git-publish>`_
|
||||||
|
|
||||||
The workflow with 'git-publish' is:
|
The workflow with 'git-publish' is:
|
||||||
|
|
||||||
|
.. code-block:: shell
|
||||||
|
|
||||||
$ git checkout master -b my-feature
|
$ git checkout master -b my-feature
|
||||||
$ # work on new commits, add your 'Signed-off-by' lines to each
|
$ # work on new commits, add your 'Signed-off-by' lines to each
|
||||||
$ git publish
|
$ git publish
|
||||||
|
@ -95,6 +106,8 @@ back to it in the future.
|
||||||
|
|
||||||
Sending v2:
|
Sending v2:
|
||||||
|
|
||||||
|
.. code-block:: shell
|
||||||
|
|
||||||
$ git checkout my-feature # same topic branch
|
$ git checkout my-feature # same topic branch
|
||||||
$ # making changes to the commits (using 'git rebase', for example)
|
$ # making changes to the commits (using 'git rebase', for example)
|
||||||
$ git publish
|
$ 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
|
found when running code built from QEMU git or upstream released sources
|
||||||
should be reported via:
|
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
|
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
|
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:
|
For additional information on bug reporting consult:
|
||||||
|
|
||||||
https://qemu.org/Contribute/ReportABug
|
* `<https://qemu.org/Contribute/ReportABug>`_
|
||||||
|
|
||||||
|
|
||||||
Contact
|
Contact
|
||||||
|
@ -127,13 +140,11 @@ Contact
|
||||||
The QEMU community can be contacted in a number of ways, with the two
|
The QEMU community can be contacted in a number of ways, with the two
|
||||||
main methods being email and IRC
|
main methods being email and IRC
|
||||||
|
|
||||||
- qemu-devel@nongnu.org
|
* `<mailto:qemu-devel@nongnu.org>`_
|
||||||
https://lists.nongnu.org/mailman/listinfo/qemu-devel
|
* `<https://lists.nongnu.org/mailman/listinfo/qemu-devel>`_
|
||||||
- #qemu on irc.oftc.net
|
* #qemu on irc.oftc.net
|
||||||
|
|
||||||
Information on additional methods of contacting the community can be
|
Information on additional methods of contacting the community can be
|
||||||
found online via the QEMU website:
|
found online via the QEMU website:
|
||||||
|
|
||||||
https://qemu.org/Contribute/StartHere
|
* `<https://qemu.org/Contribute/StartHere>`_
|
||||||
|
|
||||||
-- End
|
|
|
@ -461,7 +461,7 @@ sub top_of_kernel_tree {
|
||||||
|
|
||||||
my @tree_check = (
|
my @tree_check = (
|
||||||
"COPYING", "MAINTAINERS", "Makefile",
|
"COPYING", "MAINTAINERS", "Makefile",
|
||||||
"README", "docs", "VERSION",
|
"README.rst", "docs", "VERSION",
|
||||||
"vl.c"
|
"vl.c"
|
||||||
);
|
);
|
||||||
|
|
||||||
|
|
Loading…
Reference in New Issue