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-rw-r--r--m4/using_operator.m415
1 files changed, 15 insertions, 0 deletions
diff --git a/m4/using_operator.m4 b/m4/using_operator.m4
new file mode 100644
index 000000000000..95a9951eb346
--- /dev/null
+++ b/m4/using_operator.m4
@@ -0,0 +1,15 @@
+AC_DEFUN([AC_CXX_USING_OPERATOR],
+  [AC_CACHE_CHECK(
+      whether compiler supports using ::operator<<,
+      ac_cv_cxx_using_operator,
+      [AC_LANG_SAVE
+       AC_LANG_CPLUSPLUS
+       AC_TRY_COMPILE([#include <iostream>
+                       std::ostream& operator<<(std::ostream&, struct s);],
+                      [using ::operator<<; return 0;],
+                      ac_cv_cxx_using_operator=1,
+		      ac_cv_cxx_using_operator=0)
+      AC_LANG_RESTORE])
+  if test "$ac_cv_cxx_using_operator" = 1; then
+    AC_DEFINE(HAVE_USING_OPERATOR, 1, [define if the compiler supports using expression for operator])
+  fi])