From f020fe05a20dfcd16cd7df833dcf3cdeef770538 Mon Sep 17 00:00:00 2001
From: Carlos Santos <casantos@datacom.ind.br>
Date: Thu, 11 Feb 2016 10:58:35 -0200
Subject: [PATCH 2/2] configure.ac: check if libatomic is needed

Compilation of protobuf for PowerPC and SPARC may fail due to missing
references to __atomic_fetch_add_4 and __atomic_compare_exchange_4.

The __atomic_*() intrinsics for all sizes are provided by libatomic when
gcc is >= 4.8. This can be achieved by adding this to configure.ac:

    AC_SEARCH_LIBS([__atomic_fetch_add_4], [atomic])

Signed-off-by: Carlos Santos <casantos@datacom.ind.br>
---
 configure.ac | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/configure.ac b/configure.ac
index c07067c..88d4a0d 100644
--- a/configure.ac
+++ b/configure.ac
@@ -139,6 +139,8 @@ AM_CONDITIONAL([USE_EXTERNAL_PROTOC], [test "$with_protoc" != "no"])
 ACX_PTHREAD
 AC_CXX_STL_HASH
 
+AC_SEARCH_LIBS([__atomic_load_4], [atomic])
+
 case "$target_os" in
   mingw* | cygwin* | win*)
     ;;
-- 
2.5.0

