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Annotation of qemu/CODING_STYLE, revision 1.1

1.1     ! root        1: Qemu Coding Style
        !             2: =================
        !             3: 
        !             4: 1. Whitespace
        !             5: 
        !             6: Of course, the most important aspect in any coding style is whitespace.
        !             7: Crusty old coders who have trouble spotting the glasses on their noses
        !             8: can tell the difference between a tab and eight spaces from a distance
        !             9: of approximately fifteen parsecs.  Many a flamewar have been fought and
        !            10: lost on this issue.
        !            11: 
        !            12: QEMU indents are four spaces.  Tabs are never used, except in Makefiles
        !            13: where they have been irreversibly coded into the syntax.
        !            14: Spaces of course are superior to tabs because:
        !            15: 
        !            16:  - You have just one way to specify whitespace, not two.  Ambiguity breeds
        !            17:    mistakes.
        !            18:  - The confusion surrounding 'use tabs to indent, spaces to justify' is gone.
        !            19:  - Tab indents push your code to the right, making your screen seriously
        !            20:    unbalanced.
        !            21:  - Tabs will be rendered incorrectly on editors who are misconfigured not
        !            22:    to use tab stops of eight positions.
        !            23:  - Tabs are rendered badly in patches, causing off-by-one errors in almost
        !            24:    every line.
        !            25:  - It is the QEMU coding style.
        !            26: 
        !            27: Do not leave whitespace dangling off the ends of lines.
        !            28: 
        !            29: 2. Line width
        !            30: 
        !            31: Lines are 80 characters; not longer.
        !            32: 
        !            33: Rationale:
        !            34:  - Some people like to tile their 24" screens with a 6x4 matrix of 80x24
        !            35:    xterms and use vi in all of them.  The best way to punish them is to
        !            36:    let them keep doing it.
        !            37:  - Code and especially patches is much more readable if limited to a sane
        !            38:    line length.  Eighty is traditional.
        !            39:  - It is the QEMU coding style.
        !            40: 
        !            41: 3. Naming
        !            42: 
        !            43: Variables are lower_case_with_underscores; easy to type and read.  Structured
        !            44: type names are in CamelCase; harder to type but standing out.  Scalar type
        !            45: names are lower_case_with_underscores_ending_with_a_t, like the POSIX
        !            46: uint64_t and family.  Note that this last convention contradicts POSIX
        !            47: and is therefore likely to be changed.
        !            48: 
        !            49: Typedefs are used to eliminate the redundant 'struct' keyword.  It is the
        !            50: QEMU coding style.
        !            51: 
        !            52: 4. Block structure
        !            53: 
        !            54: Every indented statement is braced; even if the block contains just one
        !            55: statement.  The opening brace is on the line that contains the control
        !            56: flow statement that introduces the new block; the closing brace is on the
        !            57: same line as the else keyword, or on a line by itself if there is no else
        !            58: keyword.  Example:
        !            59: 
        !            60:     if (a == 5) {
        !            61:         printf("a was 5.\n");
        !            62:     } else if (a == 6) {
        !            63:         printf("a was 6.\n");
        !            64:     } else {
        !            65:         printf("a was something else entirely.\n");
        !            66:     }
        !            67: 
        !            68: An exception is the opening brace for a function; for reasons of tradition
        !            69: and clarity it comes on a line by itself:
        !            70: 
        !            71:     void a_function(void)
        !            72:     {
        !            73:         do_something();
        !            74:     }
        !            75: 
        !            76: Rationale: a consistent (except for functions...) bracing style reduces
        !            77: ambiguity and avoids needless churn when lines are added or removed.
        !            78: Furthermore, it is the QEMU coding style.

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