diff options
author | Daniel P. Berrangé <berrange@redhat.com> | 2019-08-23 17:09:24 +0100 |
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committer | Daniel P. Berrangé <berrange@redhat.com> | 2019-09-05 14:27:06 +0100 |
commit | 336a7451e8803c21a2da6e7d1eca8cfb8e8b219a (patch) | |
tree | 62b2745dc8a2549652a4aa92c157f0e1b85b8411 /CODING_STYLE | |
parent | 500efcfcf0fe2e0dae1d25637a13435ce7b6e421 (diff) |
docs: convert README, CODING_STYLE and HACKING to RST syntax
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Diffstat (limited to 'CODING_STYLE')
-rw-r--r-- | CODING_STYLE | 216 |
1 files changed, 0 insertions, 216 deletions
diff --git a/CODING_STYLE b/CODING_STYLE deleted file mode 100644 index cb8edcbb36..0000000000 --- a/CODING_STYLE +++ /dev/null @@ -1,216 +0,0 @@ -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 |