+dnl Can't use -ansi with gcc 4.5.3 on Cygwin, at least through setup
+dnl setup version 2.763, because it disables some features in the
+dnl system system header files and warns about them with -Wall. Try
+dnl to test for that generally, though still with gcc.
+if test "$GCC" = yes; then
+ AC_CACHE_CHECK([whether we can use -ansi with gcc], [nmh_cv_has_dash_ansi],
+ [nmh_saved_cppflags="$CPPFLAGS"
+ nmh_saved_cflags="$CFLAGS"
+ CPPFLAGS="-D_GNU_SOURCE"
+ CFLAGS="-ansi -Wall -Werror"
+ AC_COMPILE_IFELSE([AC_LANG_PROGRAM([#include <time.h>],[tzset();])],
+ [nmh_cv_has_dash_ansi=yes],
+ [nmh_cv_has_dash_ansi=no])
+ CPPFLAGS="$nmh_saved_cppflags"
+ CFLAGS="$nmh_saved_cflags"])
+else
+ nmh_cv_has_dash_ansi=no
+fi
+