From 8eaf14a17244aaf000b4d19e4fde4a637576939f Mon Sep 17 00:00:00 2001
From: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Date: Sun, 7 Feb 2016 21:40:47 +0100
Subject: [PATCH] configure.ac: check if libatomic is needed

The mpd source code uses the C++11 <atomic> functionality, which
internally is implemented using the __atomic_*() gcc built-ins. On
certain architectures, the __atomic_*() built-ins are implemented in
the libatomic library that comes with the rest of the gcc runtime. Due
to this, code using <atomic> might need to link against libatomic,
otherwise one hits build issues such as:

GlobalEvents.cxx:(.text._ZN12GlobalEvents4EmitENS_5EventE+0x14): undefined reference to `__atomic_fetch_or_4'

on an architecture like SPARC.

To solve this, a configure.ac check is added to know if we need to
link against libatomic or not.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
---
 configure.ac | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/configure.ac b/configure.ac
index 107b45a..8e6fab7 100644
--- a/configure.ac
+++ b/configure.ac
@@ -233,6 +233,8 @@ if test x$have_pthread_setname_np = xyes; then
 	AC_DEFINE(HAVE_PTHREAD_SETNAME_NP, 1, [Is pthread_setname_np() available?])
 fi
 
+AC_SEARCH_LIBS([__atomic_load_4], [atomic])
+
 dnl ---------------------------------------------------------------------------
 dnl Event loop selection
 dnl ---------------------------------------------------------------------------
-- 
2.6.4