CodingGuidelines: spell out post-C89 rules
Even though we have been sticking to C89, there are a few handy features we borrow from more recent C language in our codebase after trying them in weather balloons and saw that nobody screamed. Spell them out. While at it, extend the existing variable declaration rule a bit to read better with the newly spelled out rule for the for loop. Signed-off-by: Junio C Hamano <gitster@pobox.com>
Junio C Hamano committed
Jul 16, 2019 at 10:21 UTC
cc0c42975a2d9159fea5fdd053425492333c1aba
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Documentation/CodingGuidelines
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@@ -195,10 +195,30 @@ For C programs:
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by e.g. "echo DEVELOPER=1 >>config.mak".
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- We try to support a wide range of C compilers to compile Git with,
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- including old ones. That means that you should not use C99
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- initializers, even if a lot of compilers grok it.
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+ including old ones. You should not use features from newer C
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+ standard, even if your compiler groks them.
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- - Variables have to be declared at the beginning of the block.
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+ There are a few exceptions to this guideline:
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+
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+ . since early 2012 with e1327023ea, we have been using an enum
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+ definition whose last element is followed by a comma. This, like
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+ an array initializer that ends with a trailing comma, can be used
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+ to reduce the patch noise when adding a new identifer at the end.
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+
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+ . since mid 2017 with cbc0f81d, we have been using designated
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+ initializers for struct (e.g. "struct t v = { .val = 'a' };").
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+
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+ . since mid 2017 with 512f41cf, we have been using designated
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+ initializers for array (e.g. "int array[10] = { [5] = 2 }").
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+
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+ These used to be forbidden, but we have not heard any breakage
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+ report, and they are assumed to be safe.
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+
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+ - Variables have to be declared at the beginning of the block, before
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+ the first statement (i.e. -Wdeclaration-after-statement).
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+
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+ - Declaring a variable in the for loop "for (int i = 0; i < 10; i++)"
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+ is still not allowed in this codebase.
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- NULL pointers shall be written as NULL, not as 0.
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