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

[Thomas Guillem]

Applied (after a small conflict) and works for me (ie. HAVE_BSWAP* are not defined on Linux).

Will push tomorrow if nobody is against.

On Tue, Feb 27, 2018, at 05:24, Kamil Rytarowski wrote:
> 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
> 
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