Use bundled GNU regex on OS X

m4/macosx.m4

@@ -8,6 +8,13 @@ case "$target_os" in
       ;;
 esac
 
+if test "$target_darwin" = "yes"; then
+   AC_MSG_NOTICE([using bundled GNU regex on $target_os])
+   # pretend that the regex.h check failed so that we use the bundled regex code
+   ac_cv_header_regex_h=no
+   AC_DEFINE([HAVE_REGEX_H], 0, [Define to 1 if you have the <regex.h> header file.])
+fi
+
 AC_ARG_ENABLE([mac-universal], AC_HELP_STRING([--enable-mac-universal],
                                               [build a universal binary on Mac OS X @<:@no@:>@]),
               [case "${enableval}" in

src/include/re.h

@@ -23,7 +23,7 @@
 #ifndef RE_H_
 #define RE_H_
 
-#ifdef HAVE_REGEX_H
+#if HAVE_REGEX_H
 #  include <regex.h>
 #else
 #  include "compat/regex.h"

src/include/spot.h

@@ -23,7 +23,7 @@
 #ifndef SPOT_H_
 #define SPOT_H_
 
-#ifdef HAVE_REGEX_H
+#if HAVE_REGEX_H
 #  include <regex.h>
 #else
 #  include "compat/regex.h"