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authorJunio C Hamano <gitster@pobox.com>2019-07-16 17:21:20 (GMT)
committerJunio C Hamano <gitster@pobox.com>2019-07-18 22:16:04 (GMT)
commitcc0c42975a2d9159fea5fdd053425492333c1aba (patch)
tree24371f8591324080dca5ccdb5109fd631326b95f /Documentation/CodingGuidelines
parentb697d92f56511e804b8ba20ccbe7bdc85dc66810 (diff)
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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>
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@@ -195,10 +195,30 @@ For C programs:
by e.g. "echo DEVELOPER=1 >>config.mak".
- We try to support a wide range of C compilers to compile Git with,
- including old ones. That means that you should not use C99
- initializers, even if a lot of compilers grok it.
+ including old ones. You should not use features from newer C
+ standard, even if your compiler groks them.
- - Variables have to be declared at the beginning of the block.
+ There are a few exceptions to this guideline:
+
+ . since early 2012 with e1327023ea, we have been using an enum
+ definition whose last element is followed by a comma. This, like
+ an array initializer that ends with a trailing comma, can be used
+ to reduce the patch noise when adding a new identifer at the end.
+
+ . since mid 2017 with cbc0f81d, we have been using designated
+ initializers for struct (e.g. "struct t v = { .val = 'a' };").
+
+ . since mid 2017 with 512f41cf, we have been using designated
+ initializers for array (e.g. "int array[10] = { [5] = 2 }").
+
+ These used to be forbidden, but we have not heard any breakage
+ report, and they are assumed to be safe.
+
+ - Variables have to be declared at the beginning of the block, before
+ the first statement (i.e. -Wdeclaration-after-statement).
+
+ - Declaring a variable in the for loop "for (int i = 0; i < 10; i++)"
+ is still not allowed in this codebase.
- NULL pointers shall be written as NULL, not as 0.