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Re: GCC - Preserving statement expression results on stack
- From: Andrew Haley <aph-gcc at littlepinkcloud dot COM>
- To: Joe Perches <joe at perches dot com>
- Cc: gcc-help at gcc dot gnu dot org, Eric Botcazou <ebotcazou at libertysurf dot fr>
- Date: Thu, 30 Aug 2007 10:31:13 +0100
- Subject: Re: GCC - Preserving statement expression results on stack
- References: <1188426212.6062.101.camel@localhost>
Joe Perches writes:
> I know that gcc preserves stack slots for statement expressions.
>
> http://gcc.gnu.org/ml/gcc-patches/2002-02/msg00958.html
>
> What about statement expressions that return arrays?
> When does GCC free stack used by statement expression array returns?
>
> For instance:
>
> #define itoa(i) \
> ({ char tmp[16]; sprintf(tmp, "%d", i); tmp; })
>
> printf("%s %s\n", itoa(1), itoa(2));
>
> is the printf output guaranteed to be "1 2" or is it undefined?
ISO/IEC 9899:1999 (E)
6.2.1 Scopes of identifiers
2 For each different entity that an identifier designates, the
identifier is visible (i.e., can be used) only within a region of
program text called its scope.
Unless you see some gcc documentation to the contary, that's the rule.
Andrew.