maint: update copyright

[gnulib.git] / m4 / stdnoreturn.m4

diff --git a/m4/stdnoreturn.m4 b/m4/stdnoreturn.m4
index 1a44069..eea2c1e 100644 (file)
--- a/m4/stdnoreturn.m4
+++ b/m4/stdnoreturn.m4
@@ -1,22 +1,41 @@
-# Check for stdnoreturn.h.
+# Check for stdnoreturn.h that conforms to C11.
 
-dnl Copyright 2011 Free Software Foundation, Inc.
+dnl Copyright 2012-2014 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
 dnl with or without modifications, as long as this notice is preserved.
 
+# Prepare for substituting <stdnoreturn.h> if it is not supported.
+
 AC_DEFUN([gl_STDNORETURN_H],
 [
-  dnl Assume that a system-supplied stdnoreturn.h works if it exists.
-  AC_CHECK_HEADERS_ONCE([stdnoreturn.h])
+  AC_CACHE_CHECK([for working stdnoreturn.h],
+    [gl_cv_header_working_stdnoreturn_h],
+    [AC_COMPILE_IFELSE(
+       [AC_LANG_PROGRAM(
+          [[#include <stdlib.h>
+            #include <stdnoreturn.h>
+            /* Do not check for 'noreturn' after the return type.
+               C11 allows it, but it's rarely done that way
+               and circa-2012 bleeding-edge GCC rejects it when given
+               -Werror=old-style-declaration.  */
+            noreturn void foo1 (void) { exit (0); }
+            _Noreturn void foo2 (void) { exit (0); }
+            int testit (int argc, char **argv) {
+              if (argc & 1)
+                return 0;
+              (argv[0][0] ? foo1 : foo2) ();
+            }
+          ]])],
+       [gl_cv_header_working_stdnoreturn_h=yes],
+       [gl_cv_header_working_stdnoreturn_h=no])])
 
-  if test "$ac_cv_header_stdnoreturn_h" = yes; then
+  if test $gl_cv_header_working_stdnoreturn_h = yes; then
     STDNORETURN_H=''
   else
     STDNORETURN_H='stdnoreturn.h'
   fi
-  AC_SUBST([STDNORETURN_H])
 
-  AM_CONDITIONAL([GL_GENERATE_STDNORETURN_H],
-    [test $ac_cv_header_stdnoreturn_h != yes])
+  AC_SUBST([STDNORETURN_H])
+  AM_CONDITIONAL([GL_GENERATE_STDNORETURN_H], [test -n "$STDNORETURN_H"])
 ])