Get Berkeley Yacc port of the parser working again.

* parser.y (byacc_fool): New grammar nonterminal symbol and
dummy rule set.
(spec): Use dummy byacc_fool to create a fake continuation
in the grammar, so the Berkeley-Yacc-generated parser doesn't
throw a syntax error. Our YYACCEPT prevents the byacc_fool part
from consuming more than one token of lookahead.
Bison doesn't need this because it has $default actions which reduce
regardless of the lookahead token. BYacc insists on reducing only
if it can match $end (end of input), and not other tokens, which
constitute syntax errors.

1 files changed, 7 insertions, 0 deletions

diff --git a/parser.y b/parser.y
index d0ab1f59..bfa88a78 100644
--- a/parser.y
+++ b/parser.y
@@ -120,6 +120,7 @@ int yyparse(scanner_t *, parser_t *);
 %type <val> strlit chrlit quasilit quasi_items quasi_item litchars wordslit
 %type <val> wordsqlit not_a_clause
 %type <chr> regchar
+%type <val> byacc_fool
 %type <lineno> '(' '[' '@'
 
 %nonassoc LOW /* used for precedence assertion */
@@ -141,6 +142,7 @@ spec : clauses                  { parser->syntax_tree = $1; }
      | /* empty */              { parser->syntax_tree = nil; }
      | SECRET_ESCAPE_R regexpr  { parser->syntax_tree = $2; end_of_regex(scnr); }
      | SECRET_ESCAPE_E n_expr   { parser->syntax_tree = $2; YYACCEPT; }
+       byacc_fool               { internal_error("notreached"); }
      | SECRET_ESCAPE_E          { if (yychar == YYEOF) {
                                     parser->syntax_tree = nao;
                                     YYACCEPT;
@@ -156,6 +158,11 @@ spec : clauses                  { parser->syntax_tree = $1; }
 
      ;
 
+/* Hack needed for Berkeley Yacc */
+byacc_fool : n_expr { internal_error("notreached"); }
+           | { internal_error("notreached"); }
+           ;
+
 clauses : clauses_rev           { $$ = nreverse($1); }
 
 clauses_rev : clause                    { $$ = check_for_include(cons($1, nil)); }