Parse error handling improvements.

* parser.l (prepared_error_message): New static variable.
(yyerror): Emit and clear prepared error message.
(yyerrprepf): New static function.
(yybadtoken): Function moved into parser.y.
(grammar): For irrecoverable lexical errors, stash error message
with yyerrprepf and return the special error token ERRTOK to generate a
syntax error. I could find no other interface to the parser to make it
cleanly exit.

* parser.y (ERRTOK): New terminal symbol, does not appear anywhere
in the grammar.
(spec): Bail after 8 errors, recover to nearest newline, and
use yyerrok to clear error situation.
(YYEOF): Provided by Bison, conditionally defined for other yacc-s.
(yybadtoken): Function moved from parser.l.  Checks for the next
token being YYEMPTY or YYEOF, and also handles ERRTOK.

* stream.c (vformat_to_string): New function.
(format): If stream is nil, format to string and return it.

* stream.h (vformat_to_string): Declared.

1 files changed, 10 insertions, 2 deletions

diff --git a/stream.c b/stream.c
index bb9641df..6062d91e 100644
--- a/stream.c
+++ b/stream.c
@@ -998,8 +998,16 @@ toobig:
   internal_error("ridiculous precision or field width in format");
 }
 
+val vformat_to_string(val fmtstr, va_list vl)
+{
+  val stream = make_string_output_stream();
+  (void) vformat(stream, fmtstr, vl);
+  return get_string_from_stream(stream);
+}
+
 val format(val stream, val str, ...)
 {
+  val st = or2(stream, make_string_output_stream());
   type_check (stream, COBJ);
   type_assert (stream->co.cls == stream_s, (lit("~a is not a stream"),
                                              stream, nao));
@@ -1008,9 +1016,9 @@ val format(val stream, val str, ...)
     va_list vl;
     val ret;
     va_start (vl, str);
-    ret = vformat(stream, str, vl);
+    ret = vformat(st, str, vl);
     va_end (vl);
-    return ret;
+    return (stream) ? ret : get_string_from_stream(st);
   }
 }