Merge branch '3971_sighandler_t'

* 3971_sighandler_t:
  Ticket #3971: clarify sighandler_t usage in non-GNU OSes.

m4.include/mc-tests.m4

@@ -42,6 +42,12 @@ AC_DEFUN([mc_UNIT_TESTS],[
     fi
     AM_CONDITIONAL(HAVE_TESTS, test x"$have_check" = "xyes")
 
+    dnl sighandler_t is GNU extension
+    dnl AC_USE_SYSTEM_EXTENSIONS is reguired
+    AC_CHECK_TYPES([sighandler_t], [], [], [
+        #include <signal.h>
+    ])
+
     # on cygwin, the linker does not accept the "-z" option
     case $host_os in
         cygwin*)

tests/lib/utilunix__my_system-common.c

@@ -28,6 +28,11 @@
 
 #include "lib/vfs/vfs.h"
 
+/* sighandler_t is GNU extension */
+#ifndef HAVE_SIGHANDLER_T
+typedef void (*sighandler_t) (int);
+#endif
+
 /* --------------------------------------------------------------------------------------------- */
 
 /* @CapturedValue */