m4: Fix how pcre2_substitute_callout_block is checked

The old way was very wrong

diff --git a/m4/want_pcre.m4 b/m4/want_pcre.m4
index f013aaad82b3166ffc06aeaa79fbb86f64b83752..692a67317793d7324325bf526512824f3aac6953 100644 (file)
--- a/m4/want_pcre.m4
+++ b/m4/want_pcre.m4
@@ -14,7 +14,12 @@ AC_DEFUN([DOVECOT_WANT_PCRE], [
   AS_IF([test "$have_pcre" != "no"], [
     old_CFLAGS="$CFLAGS"
     CFLAGS="$CFLAGS $LIBPCRE_CFLAGS"
-    AC_CHECK_FUNCS([pcre2_substitute_callout_block])
+    AC_CHECK_DECL([pcre2_substitute_callout_block],
+      AC_DEFINE(HAVE_PCRE2_SUBSTITUTE_CALLOUT_BLOCK,,
+        [Define if you have pcre2_substitute_callout_block]),,
+      [[#define PCRE2_CODE_UNIT_WIDTH 0]]
+      [[#include <pcre2.h>]]
+    )
     CFLAGS="$old_CFLAGS"
     AC_DEFINE(HAVE_LIBPCRE,, [Define if you have libpcre2 backed regular expressions])
   ])