From 3f2546b2ef55b661fd8dd69682b38992225e86f6 Mon Sep 17 00:00:00 2001 From: fishsoupisgood Date: Mon, 29 Apr 2019 01:17:54 +0100 Subject: Initial import of qemu-2.4.1 --- CODING_STYLE | 107 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 107 insertions(+) create mode 100644 CODING_STYLE (limited to 'CODING_STYLE') diff --git a/CODING_STYLE b/CODING_STYLE new file mode 100644 index 00000000..d46cfa5f --- /dev/null +++ b/CODING_STYLE @@ -0,0 +1,107 @@ +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. + +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. -- cgit v1.2.3