parser: gc bug in token.

The parser maintains some token objects for one parse job to
the next in the tok_pushback and recent_tok arrays.  When the
recent_tok is assigned into the parser, it could be a
wrong-way assignment: the parser is a gen 1 object,
yet the token's semantic value of type val is a gen 0.

* parser.c (lisp_parse_impl, txr_parse): Before re-enabling
gc, indicate that the parser object may have been mutated by a
wrong-way assignment using the mut macro.

* txr.c (txr_main): Likewise.

1 files changed, 2 insertions, 0 deletions

diff --git a/parser.c b/parser.c
index 368ecebd..85b80202 100644
--- a/parser.c
+++ b/parser.c
@@ -665,6 +665,7 @@ static val lisp_parse_impl(val self, enum prime_parser prime,
   for (;;) {
     int gc = gc_state(0);
     parse(pi, if3(std_error != std_null, name, lit("")), prime);
+    mut(parser);
     gc_state(gc);
 
     if (pi->syntax_tree == nao && pi->errors == 0 && !pi->eof)
@@ -823,6 +824,7 @@ val txr_parse(val source_in, val error_stream,
 
   uw_unwind {
     dyn_env = saved_dyn;
+    mut(parser_obj);
     gc_state(gc);
     if (!loading)
       uw_release_deferred_warnings();