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

[Thomas Guillem]

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
> >
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> 
> 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

> -- 
> Remi Denis-Courmont
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