parsergen: guard against tos going negative.

Don't continue the parse loop if tos hits zero.

Signed-off-by: NeilBrown <neil@brown.name>

diff --git a/csrc/parsergen.mdc b/csrc/parsergen.mdc
index da9335ed0df1794fe49c35030272e333956259a3..a913cb912c77cf5a977e835b4bd1ec8ac212929b 100644 (file)
--- a/csrc/parsergen.mdc
+++ b/csrc/parsergen.mdc
@@ -2990,7 +2990,7 @@ checks if a given token is in any of these look-ahead sets.
                void *ret = NULL;
 
                shift(&p, TK_eof, 0, 1, NULL, states);
-               while (!accepted) {
+               while (!accepted && p.tos > 0) {
                        struct token *err_tk;
                        struct frame *tos = &p.stack[p.tos-1];
                        if (!tk)