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

[Kamil Rytarowski]

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