- memset (&re_regs, 0, sizeof (re_regs));
- re_buffer.allocated = 2 * len;
- re_buffer.buffer = (unsigned char *) xmalloc (re_buffer.allocated);
- re_buffer.translate = 0;
- re_syntax_options = RE_SYNTAX_POSIX_BASIC;
- errmsg = re_compile_pattern (pv->u.s, len, &re_buffer);
- if (errmsg) {
- bb_error_msg_and_die("%s", errmsg);
- }
-
- len = re_match (&re_buffer, sv->u.s, strlen (sv->u.s), 0, &re_regs);
- if (len >= 0) {
+ memset (re_regs, 0, sizeof (*re_regs));
+ if( regcomp (&re_buffer, pv->u.s, 0) != 0 )
+ bb_error_msg_and_die("Invalid regular expression");
+
+ /* expr uses an anchored pattern match, so check that there was a
+ * match and that the match starts at offset 0. */
+ if (regexec (&re_buffer, sv->u.s, NMATCH, re_regs, 0) != REG_NOMATCH &&
+ re_regs[0].rm_so == 0) {