atomic: check if -latomic is required for std::atomic

* configure.ac,
m4/l_atomic.m4,
python/Makefile.am,
tests/Makefile.am: Here.

configure.ac

@@ -79,6 +79,9 @@ AX_CHECK_COMPILE_FLAG([-std=c11], [CFLAGS="$CFLAGS -std=c11"])
 
 gl_INIT
 
+dnl Check if -latomic is required for <std::atomic>
+CHECK_ATOMIC
+
 # Use -Werror since using -fvisibility under MinGW is only a warning.
 # (The option is ignored anyway since this does not make sense under windows).
 AX_CHECK_COMPILE_FLAG([-Werror -fvisibility=hidden],

m4/l_atomic.m4

@@ -0,0 +1,40 @@
+dnl Copyright (c) 2015 Tim Kosse <tim.kosse@filezilla-project.org>
+dnl Copying and distribution of this file, with or without modification, are
+dnl permitted in any medium without royalty provided the copyright notice
+dnl and this notice are preserved. This file is offered as-is, without any
+dnl warranty.
+
+# Some versions of gcc/libstdc++ require linking with -latomic if
+# using the C++ atomic library.
+#
+# Sourced from http://bugs.debian.org/797228
+
+m4_define([_CHECK_ATOMIC_testbody], [[
+  #include <atomic>
+  #include <cstdint>
+  int main() {
+    std::atomic<int64_t> a{};
+    int64_t v = 5;
+    int64_t r = a.fetch_add(v);
+    return static_cast<int>(r);
+  }
+]])
+
+AC_DEFUN([CHECK_ATOMIC], [
+  AC_LANG_PUSH(C++)
+  AC_MSG_CHECKING([whether std::atomic can be used without link library])
+  AC_LINK_IFELSE([AC_LANG_SOURCE([_CHECK_ATOMIC_testbody])],[
+      AC_MSG_RESULT([yes])
+    ],[
+      AC_MSG_RESULT([no])
+      LIBS="$LIBS -latomic"
+      AC_MSG_CHECKING([whether std::atomic needs -latomic])
+      AC_LINK_IFELSE([AC_LANG_SOURCE([_CHECK_ATOMIC_testbody])],[
+          AC_MSG_RESULT([yes])
+        ],[
+          AC_MSG_RESULT([no])
+          AC_MSG_FAILURE([cannot figure out how to use std::atomic])
+        ])
+    ])
+  AC_LANG_POP
+])

python/Makefile.am

@@ -23,7 +23,7 @@
 AUTOMAKE_OPTIONS = subdir-objects
 
 AM_CPPFLAGS = -I$(PYTHONINC) -I$(top_builddir) -I$(top_srcdir) \
-	      $(BUDDY_CPPFLAGS) -lpthread -latomic -DSWIG_TYPE_TABLE=spot
+	      $(BUDDY_CPPFLAGS) -lpthread -DSWIG_TYPE_TABLE=spot
 
 SWIGFLAGS = -c++ -python -py3 -O -MD
 
@@ -71,7 +71,7 @@ am__depfiles_remade = ./$(DEPDIR)/buddy_wrap.Plo \
 
 spot__impl_la_SOURCES = spot/impl_wrap.cxx
 spot__impl_la_LDFLAGS = -avoid-version -module $(SYMBOLIC_LDFLAGS)
-spot__impl_la_LIBADD = $(top_builddir)/spot/libspot.la -lpthread -latomic
+spot__impl_la_LIBADD = $(top_builddir)/spot/libspot.la -lpthread
 
 am__depfiles_remade += ./spot/$(DEPDIR)/impl_wrap.Pcxx
 @AMDEP_TRUE@@am__include@ @am__quote@./spot/$(DEPDIR)/impl_wrap.Pcxx@am__quote@ # am--include-marker
@@ -92,7 +92,7 @@ spot__ltsmin_la_SOURCES = spot/ltsmin_wrap.cxx
 spot__ltsmin_la_LDFLAGS = -avoid-version -module $(SYMBOLIC_LDFLAGS)
 spot__ltsmin_la_LIBADD = $(top_builddir)/spot/libspot.la \
                        $(top_builddir)/spot/ltsmin/libspotltsmin.la \
-					   -lpthread -latomic
+					   -lpthread
 
 am__depfiles_remade += ./spot/$(DEPDIR)/ltsmin_wrap.Pcxx
 @AMDEP_TRUE@@am__include@ @am__quote@./spot/$(DEPDIR)/ltsmin_wrap.Pcxx@am__quote@ # am--include-marker
@@ -111,7 +111,7 @@ spot__gen_la_SOURCES = spot/gen_wrap.cxx
 spot__gen_la_LDFLAGS = -avoid-version -module $(SYMBOLIC_LDFLAGS)
 spot__gen_la_LIBADD = $(top_builddir)/spot/libspot.la \
                        $(top_builddir)/spot/gen/libspotgen.la \
-					   -lpthread -latomic
+					   -lpthread
 
 am__depfiles_remade += ./spot/$(DEPDIR)/gen_wrap.Pcxx
 @AMDEP_TRUE@@am__include@ @am__quote@./spot/$(DEPDIR)/gen_wrap.Pcxx@am__quote@ # am--include-marker

tests/Makefile.am

@@ -27,7 +27,7 @@ AM_CPPFLAGS = -I$(top_builddir) -I$(top_srcdir) $(BUDDY_CPPFLAGS) \
 AM_CXXFLAGS = $(WARNING_CXXFLAGS)
 LDADD = $(top_builddir)/spot/libspot.la \
        $(top_builddir)/buddy/src/libbddx.la \
-       $(LIBLTDL) -lpthread -latomic
+       $(LIBLTDL) -lpthread
 
 # Explicitely set it to avoid default value ".test"
 TEST_EXTENSIONS =
@@ -461,7 +461,7 @@ check_PROGRAMS += ltsmin/modelcheck
 check_PROGRAMS += ltsmin/testconvert
 ltsmin_modelcheck_CPPFLAGS = -I$(top_builddir) -I$(top_srcdir) \
 	$(BUDDY_CPPFLAGS) \-I$(top_builddir)/lib -I$(top_srcdir)/lib
-ltsmin_modelcheck_CXXFLAGS = $(CXXFLAGS) -pthread -latomic
+ltsmin_modelcheck_CXXFLAGS = $(CXXFLAGS) -pthread
 ltsmin_modelcheck_SOURCES = ltsmin/modelcheck.cc
 ltsmin_modelcheck_LDADD =  \
   $(top_builddir)/bin/libcommon.a		\
@@ -471,7 +471,7 @@ ltsmin_modelcheck_LDADD =  \
 
 ltsmin_testconvert_CPPFLAGS = -I$(top_builddir) -I$(top_srcdir) \
 	$(BUDDY_CPPFLAGS) \-I$(top_builddir)/lib -I$(top_srcdir)/lib
-ltsmin_testconvert_CXXFLAGS = $(CXXFLAGS) -pthread -latomic
+ltsmin_testconvert_CXXFLAGS = $(CXXFLAGS) -pthread
 ltsmin_testconvert_SOURCES = ltsmin/testconvert.cc
 ltsmin_testconvert_LDADD =  \
   $(top_builddir)/bin/libcommon.a		\