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![Ramsay Jones](/assets/img/avatar_default.png)
commit51ea551
("make sure byte swapping is optimal for git" 2009-08-18) introduced a "sane definition for ntohl()/htonl()" for use on some GNU C platforms. Unfortunately, for some of these platforms, this results in the introduction of a problem which is essentially the reverse of a problem that commit6e1c234
("Fix some warnings (on cygwin) to allow -Werror" 2008-07-3) was intended to fix. In particular, on platforms where the uint32_t type is defined to be unsigned long, the return type of the new ntohl()/htonl() is causing gcc to issue printf format warnings, such as: warning: long unsigned int format, unsigned int arg (arg 3) (nine such warnings, covering six different files). The earlier commit (6e1c234
) needed to suppress these same warnings, except that the types were in the opposite direction; namely the format specifier ("%u") was 'unsigned int' and the argument type (ie the return type of ntohl()) was 'long unsigned int' (aka uint32_t). In order to suppress these warnings, the earlier commit used the (C99) PRIu32 format specifier, since the definition of this macro is suitable for use with the uint32_t type on that platform. This worked because the return type of the (original) platform ntohl()/htonl() functions was uint32_t. In order to suppress these warnings, we change the return type of the new byte swapping functions in the compat/bswap.h header file from 'unsigned int' to uint32_t. Signed-off-by: Ramsay Jones <ramsay@ramsay1.demon.co.uk> Acked-by: Nicolas Pitre <nico@fluxnic.net> Signed-off-by: Jeff King <peff@peff.net>
37 lines
867 B
C
37 lines
867 B
C
/*
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* Let's make sure we always have a sane definition for ntohl()/htonl().
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* Some libraries define those as a function call, just to perform byte
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* shifting, bringing significant overhead to what should be a simple
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* operation.
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*/
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/*
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* Default version that the compiler ought to optimize properly with
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* constant values.
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*/
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static inline uint32_t default_swab32(uint32_t val)
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{
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return (((val & 0xff000000) >> 24) |
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((val & 0x00ff0000) >> 8) |
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((val & 0x0000ff00) << 8) |
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((val & 0x000000ff) << 24));
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}
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#if defined(__GNUC__) && (defined(__i386__) || defined(__x86_64__))
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#define bswap32(x) ({ \
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uint32_t __res; \
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if (__builtin_constant_p(x)) { \
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__res = default_swab32(x); \
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} else { \
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__asm__("bswap %0" : "=r" (__res) : "0" (x)); \
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} \
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__res; })
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#undef ntohl
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#undef htonl
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#define ntohl(x) bswap32(x)
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#define htonl(x) bswap32(x)
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#endif
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