mirror of
https://github.com/qemu/qemu.git
synced 2024-11-30 07:13:38 +08:00
e939c6ed61
We had an unwritten rule about declarations having to be at beginning of blocks. Make it a written rule. Signed-off-by: Eduardo Habkost <ehabkost@redhat.com> Reviewed-by: Stefan Weil <sw@weilnetz.de> Reviewed-by: Markus Armbruster <armbru@redhat.com> Reviewed-by: Peter Maydell <peter.maydell@linaro.org> Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
94 lines
3.3 KiB
Plaintext
94 lines
3.3 KiB
Plaintext
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 have 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.
|
|
|
|
2. Line width
|
|
|
|
Lines are 80 characters; not longer.
|
|
|
|
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.
|
|
- 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 not allowed; declarations should be at the beginning of blocks. In other
|
|
words, the code should not generate warnings if using GCC's
|
|
-Wdeclaration-after-statement option.
|