Adding upstream version 4:7.4.7.upstream/4%7.4.7upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 41 insertions, 0 deletions

diff --git a/m4/l_atomic.m4 b/m4/l_atomic.m4
new file mode 100644
index 000000000..6e011ebab
--- /dev/null
+++ b/m4/l_atomic.m4
@@ -0,0 +1,41 @@
+# 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_L_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_L_ATOMIC], [
+
+  AC_LANG_PUSH(C++)
+
+  AC_MSG_CHECKING([whether std::atomic can be used without link library])
+
+  AC_LINK_IFELSE([AC_LANG_SOURCE([_CHECK_L_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_L_ATOMIC_testbody])],[
+          AC_MSG_RESULT([yes])
+          ATOMIC_LIB=-latomic
+        ],[
+          AC_MSG_RESULT([no])
+          AC_MSG_FAILURE([cannot figure our how to use std::atomic])
+        ])
+    ])
+
+  AC_LANG_POP
+])