[vlc-devel] [PATCH v2] configure: Detect bswap* functions

[Kamil Rytarowski]

On 05.03.2018 12:54, Thomas Guillem wrote:
> 
> On Mon, Mar 5, 2018, at 12:26, Rémi Denis-Courmont wrote:
>> Le 27 février 2018 06:24:03 GMT+02:00, Kamil Rytarowski <n54 at gmx.com> a écrit :
>>> Attempt to detect bswap16, bswap32 and bswap64 on a target OS.
>>>
>>> Use a generic approach with AC_LINK_IFELSE() and AC_LANG_PROGRAM()
>>> to detect these functions, because their symbols can be mangled in
>>> libc.
>>>
>>> This is required for the NetBSD case:
>>> - bswap16's symbol in the libc is renamed to __bswap16,
>>> - bswap32's symbol renamed to __bswap32,
>>> - bswap64's symbol not renamed and kept as bswap64.
>>>
>>> This revision corrects build failure on NetBSD.
>>> ---
>>> configure.ac         | 37 +++++++++++++++++++++++++++++++++++++
>>> include/vlc_common.h |  6 ++++++
>>> 2 files changed, 43 insertions(+)
>>>
>>> diff --git a/configure.ac b/configure.ac
>>> index 4184012912..0007dc8e2a 100644
>>> --- a/configure.ac
>>> +++ b/configure.ac
>>> @@ -847,6 +847,43 @@ AC_CHECK_HEADERS([features.h getopt.h linux/dccp.h
>>> linux/magic.h mntent.h sys/ev
>>> dnl  MacOS
>>> AC_CHECK_HEADERS([xlocale.h])
>>>
>>> +dnl  byte swap
>>> +AC_MSG_CHECKING([bswap16])
>>> +AC_LINK_IFELSE([AC_LANG_PROGRAM([[
>>> +#include <sys/types.h>
>>> +#include <stdint.h>]], [
>>> +uint16_t A = bswap16(1);
>>> +])], [
>>> +  AC_MSG_RESULT([yes])
>>> +  AC_DEFINE([HAVE_BSWAP16], [1], [Define to 1 if you have the
>>> `bswap16` function.])
>>> +], [
>>> +  AC_MSG_RESULT([no])
>>> +])
>>> +
>>> +AC_MSG_CHECKING([bswap32])
>>> +AC_LINK_IFELSE([AC_LANG_PROGRAM([[
>>> +#include <sys/types.h>
>>> +#include <stdint.h>]], [
>>> +uint32_t A = bswap32(1);
>>> +])], [
>>> +  AC_MSG_RESULT([yes])
>>> +  AC_DEFINE([HAVE_BSWAP32], [1], [Define to 1 if you have the
>>> `bswap32` function.])
>>> +], [
>>> +  AC_MSG_RESULT([no])
>>> +])
>>> +
>>> +AC_MSG_CHECKING([bswap64])
>>> +AC_LINK_IFELSE([AC_LANG_PROGRAM([[
>>> +#include <sys/types.h>
>>> +#include <stdint.h>]], [
>>> +uint64_t A = bswap64(1);
>>> +])], [
>>> +  AC_MSG_RESULT([yes])
>>> +  AC_DEFINE([HAVE_BSWAP64], [1], [Define to 1 if you have the
>>> `bswap64` function.])
>>> +], [
>>> +  AC_MSG_RESULT([no])
>>> +])
>>> +
>>> dnl LP64 and LLP64 architectures had better define ssize_t by
>>> themselves...
>>> AH_TEMPLATE(ssize_t, [Define to `int' if <stddef.h> does not define.])
>>> dnl ` (fix VIM syntax highlight
>>> AC_CHECK_TYPE(ssize_t,, [
>>> diff --git a/include/vlc_common.h b/include/vlc_common.h
>>> index bab06bcf41..96646d29ce 100644
>>> --- a/include/vlc_common.h
>>> +++ b/include/vlc_common.h
>>> @@ -752,13 +752,16 @@ VLC_USED static inline int vlc_popcount(unsigned
>>> long long x)
>>> }
>>> #endif
>>>
>>> +#ifndef HAVE_BSWAP16
>>> /** Byte swap (16 bits) */
>>> VLC_USED
>>> static inline uint16_t (bswap16)(uint16_t x)
>>> {
>>>     return (x << 8) | (x >> 8);
>>> }
>>> +#endif
>>>
>>> +#ifndef HAVE_BSWAP32
>>> /** Byte swap (32 bits) */
>>> VLC_USED
>>> static inline uint32_t (bswap32)(uint32_t x)
>>> @@ -772,7 +775,9 @@ static inline uint32_t (bswap32)(uint32_t x)
>>>          | ((x & 0xFF000000) >> 24);
>>> #endif
>>> }
>>> +#endif
>>>
>>> +#ifndef HAVE_BSWAP64
>>> /** Byte swap (64 bits) */
>>> VLC_USED
>>> static inline uint64_t (bswap64)(uint64_t x)
>>> @@ -800,6 +805,7 @@ static inline uint64_t (bswap64)(uint64_t x)
>>> #endif
>>> }
>>> /** @} */
>>> +#endif
>>>
>>> /**
>>>  * \defgroup overflow Overflowing arithmetic
>>> -- 
>>> 2.16.1
>>>
>>> _______________________________________________
>>> vlc-devel mailing list
>>> To unsubscribe or modify your subscription options:
>>> https://mailman.videolan.org/listinfo/vlc-devel
>>
>> Does this not break the test suite? Public headers cannot depend on config.h.
> 
> This didn't break the test suite, but indeed public headers can't depend on config.h


OK, I will rename the homegrown bswap* functions to to vlc_bswap*().

Alternatively I could use a `defined(__NetBSD__)` check.

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