do not treat \0 as a backref in BRE

The valid BRE backref tokens are \1 .. \9, and 0 is not a special
character either so \0 is undefined by the standard.

Such undefined escaped characters are treated as literal characters
currently, following existing practice, so \0 is the same as 0.

diff --git a/src/regex/regcomp.c b/src/regex/regcomp.c
index 4d80cb1c602ca5d53848c4535db0f1cb88d85aee..dfa9727c5f3601aaa27e864467bd818f72f89127 100644 (file)
--- a/src/regex/regcomp.c
+++ b/src/regex/regcomp.c
@@ -839,7 +839,7 @@ static reg_errcode_t parse_atom(tre_parse_ctx_t *ctx, const char *s)
                        s--;
                        break;
                default:
-                       if (!ere && isdigit(*s)) {
+                       if (!ere && (unsigned)*s-'1' < 9) {
                                /* back reference */
                                int val = *s - '0';
                                node = tre_ast_new_literal(ctx->mem, BACKREF, val, ctx->position);