Use proper quoting so brackets appear in the test program.

diff --git a/m4/regex.m4 b/m4/regex.m4
index 66b39c3aea339fd672c3477d18aae664e32b1aa9..f546dd7bcdc5ae6e98fc0c918acea197fdcb4f21 100644 (file)
--- a/m4/regex.m4
+++ b/m4/regex.m4
@@ -30,9 +30,10 @@ AC_DEFUN(jm_INCLUDED_REGEX,
            const char *s;
            struct re_registers regs;
            re_set_syntax (RE_SYNTAX_POSIX_EGREP);
-           /* Add this third left square bracket, [, to balance the
-              three right ones below.  Otherwise autoconf-2.14 chokes.  */
+           /* These two brackets, `[[' and the one in the comment below serve
+              to quote the brackets (unbalanced) in the following line.  */
            s = re_compile_pattern ("a[[:]:]]b\n", 9, &regex);
+           /* This bracket `]' helps quote the unbalanced expression above.  */
            /* This should fail with _Invalid character class name_ error.  */
            if (!s)
              exit (1);