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Re: [PATCH 2/8] compat: make gcc bswap an inline function

From
Jonathan Nieder <jrnieder@gmail.com>
Date
Mar 16, 2011, 09:31 UTC
Message-ID
<20110316093108.GB7886@elie>
In-Reply-To
<4D808126.8070706@viscovery.net>
Johannes Sixt wrote:
> Am 3/16/2011 8:00, schrieb Jonathan Nieder:
Show 7 quoted lines
>> +static inline uint32_t git_bswap32(uint32_t x)
>> +{
>> +	uint32_t result;
>> +	if (__builtin_constant_p(x))
>
> Can this predicate ever be true? Isn't it false even if the function is
> inlined?
It's true if x is a constant.

$ cat test.c #if 0 gcc -Wall -W -O -o tryit "$0" exec ./tryit #else #include <stdio.h> #include <stdint.h>

#ifdef __GNUC__
static inline int constant(uint32_t x)
{
	return __builtin_constant_p(x);
}
#else
static inline int constant(uint32_t x) { return 0; }
#endif
int main(void)
{
	printf("%d\n", constant(3 + 5));
	return 0;
}
#endif
$ ./test.c
1
Previous: Johannes SixtNext: Junio C Hamano
Message 22 of 34 in “reflog: silence -O3 -Wuninitialized warning”
  1. reflog: silence -O3 -Wuninitialized warningJonathan Nieder, Mar 16, 2011
  2. declare 1-bit bitfields to be unsignedJonathan Nieder, Mar 16, 2011
  3. Junio C HamanoMar 16, 2011
  4. Nguyen Thai Ngoc DuyMar 16, 2011
  5. Junio C HamanoMar 16, 2011
  6. Jonathan NiederMar 16, 2011
  7. Johannes SixtMar 16, 2011
  8. Jonathan NiederMar 16, 2011
  9. Johannes SixtMar 16, 2011
  10. Jonathan NiederMar 16, 2011
  11. 0/6 silence -Wuninitialized warnings that previously used the a = a trickJonathan Nieder, Mar 16, 2011
  12. 1/6 match-trees: kill off remaining -Wuninitialized warningJonathan Nieder, Mar 16, 2011
  13. 2/6 run-command: initialize failed_errno to 0Jonathan Nieder, Mar 16, 2011
  14. 3/6 diff --submodule: suppress -Wuninitialized warning by initializing to NULLJonathan Nieder, Mar 16, 2011
  15. 4/6 rsync transport: clarify insert_packed_refsJonathan Nieder, Mar 16, 2011
  16. 5/6 wt-status: protect against invalid change_typeJonathan Nieder, Mar 16, 2011
  17. 6/6 fast-import: suppress -Wuninitialized warning by initializing to NULLJonathan Nieder, Mar 16, 2011
  18. 0/8 more warnings and cleanupsJonathan Nieder, Mar 16, 2011
  19. 1/8 enums: omit trailing comma for portabilityJonathan Nieder, Mar 16, 2011
  20. 2/8 compat: make gcc bswap an inline functionJonathan Nieder, Mar 16, 2011
  21. Johannes SixtMar 16, 2011
  22. Jonathan NiederMar 16, 2011
  23. Junio C HamanoMar 16, 2011
  24. 3/8 svn-fe: do not use "return" for tail call returning voidJonathan Nieder, Mar 16, 2011
  25. 4/8 vcs-svn: remove spurious semicolonsJonathan Nieder, Mar 16, 2011
  26. Junio C HamanoMar 16, 2011
  27. Jonathan NiederMar 16, 2011
  28. 5/8 standardize brace placement in struct definitionsJonathan Nieder, Mar 16, 2011
  29. Junio C HamanoMar 18, 2011
  30. 6/8 branch: split off function that writes tracking info and commit subjectJonathan Nieder, Mar 16, 2011
  31. 7/8 cherry: split off function to print output linesJonathan Nieder, Mar 16, 2011
  32. 8/8 diff --submodule: split into bite-sized piecesJonathan Nieder, Mar 16, 2011
  33. Jens LehmannMar 16, 2011
  34. Jonathan NiederMar 16, 2011

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