Import warnings.m4 from gnulib bb41ff0b7782

This uses AC_LINK_ELSE instead of AC_COMPILE_ELSE
which should detect failures a bit better

diff --git a/m4/warnings.m4 b/m4/warnings.m4
index 184873283bbc51b4c4e7330a922926bcd71e8723..5ae01def133fb451019e908a8056aff7b4988e7e 100644 (file)
--- a/m4/warnings.m4
+++ b/m4/warnings.m4
@@ -1,5 +1,5 @@
-# warnings.m4 serial 8
-dnl Copyright (C) 2008-2013 Free Software Foundation, Inc.
+# warnings.m4 serial 11
+dnl Copyright (C) 2008-2015 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.
@@ -25,15 +25,24 @@ m4_ifdef([AS_VAR_APPEND],
 AC_DEFUN([gl_COMPILER_OPTION_IF],
 [AS_VAR_PUSHDEF([gl_Warn], [gl_cv_warn_[]_AC_LANG_ABBREV[]_$1])dnl
 AS_VAR_PUSHDEF([gl_Flags], [_AC_LANG_PREFIX[]FLAGS])dnl
+AS_LITERAL_IF([$1],
+  [m4_pushdef([gl_Positive], m4_bpatsubst([$1], [^-Wno-], [-W]))],
+  [gl_positive="$1"
+case $gl_positive in
+  -Wno-*) gl_positive=-W`expr "X$gl_positive" : 'X-Wno-\(.*\)'` ;;
+esac
+m4_pushdef([gl_Positive], [$gl_positive])])dnl
 AC_CACHE_CHECK([whether _AC_LANG compiler handles $1], m4_defn([gl_Warn]), [
   gl_save_compiler_FLAGS="$gl_Flags"
-  gl_AS_VAR_APPEND(m4_defn([gl_Flags]), [" $gl_unknown_warnings_are_errors $1"])
-  AC_COMPILE_IFELSE([m4_default([$4], [AC_LANG_PROGRAM([])])],
-                    [AS_VAR_SET(gl_Warn, [yes])],
-                    [AS_VAR_SET(gl_Warn, [no])])
+  gl_AS_VAR_APPEND(m4_defn([gl_Flags]),
+    [" $gl_unknown_warnings_are_errors ]m4_defn([gl_Positive])["])
+  AC_LINK_IFELSE([m4_default([$4], [AC_LANG_PROGRAM([])])],
+                 [AS_VAR_SET(gl_Warn, [yes])],
+                 [AS_VAR_SET(gl_Warn, [no])])
   gl_Flags="$gl_save_compiler_FLAGS"
 ])
 AS_VAR_IF(gl_Warn, [yes], [$2], [$3])
+m4_popdef([gl_Positive])dnl
 AS_VAR_POPDEF([gl_Flags])dnl
 AS_VAR_POPDEF([gl_Warn])dnl
 ])