Re: [PATCH 1/5][GIMPLE FE] PR testsuite/80580. Handle missing labels in goto statements

[Richard Biener <richard.guenther@gmail.com>]

On Mon, May 1, 2017 at 8:04 PM, Mikhail Maltsev <maltsevm@gmail.com> wrote:
> The first problem happens because we don't check for missing labels when parsing
> 'goto' statements. I.e.:
>
> __GIMPLE() void fn1() {
>   if (1)
>     goto
> }
>
> The fix is pretty obvious: just add a check.
> My question is: which functions should I use to produce diagnostics? The
> surrounding code uses 'c_parser_error', but this function does not handle
> locations very well (in fact, it uses input_location).

Certainly an improvement.  I suppose we can do better error recovery
for cases like

 if (1)
   goto
 else
   goto bar;

but I guess this is better than nothing.

And yes, we use c_parser_error -- input_location should be ok but here
we just peek which may upset the parser.  Maybe it works better
when consuming the token before issueing the error?  Thus

Index: gcc/c/gimple-parser.c
===================================================================
--- gcc/c/gimple-parser.c       (revision 247498)
+++ gcc/c/gimple-parser.c       (working copy)
@@ -1315,8 +1315,8 @@ c_parser_gimple_if_stmt (c_parser *parse
       loc = c_parser_peek_token (parser)->location;
       c_parser_consume_token (parser);
       label = c_parser_peek_token (parser)->value;
-      t_label = lookup_label_for_goto (loc, label);
       c_parser_consume_token (parser);
+      t_label = lookup_label_for_goto (loc, label);
       if (! c_parser_require (parser, CPP_SEMICOLON, "expected %<;%>"))
        return;
     }

?

Patch is ok with or without this adjustment (and testcase adjustment).

Thanks,
Richard.

> --
> Regards,
>    Mikhail Maltsev
>
> gcc/testsuite/ChangeLog:
>
> 2017-05-01  Mikhail Maltsev  <maltsevm@gmail.com>
>
>         * gcc.dg/gimplefe-error-4.c: New test.
>         * gcc.dg/gimplefe-error-5.c: New test.
>
>
> gcc/c/ChangeLog:
>
> 2017-05-01  Mikhail Maltsev  <maltsevm@gmail.com>
>
>         * gimple-parser.c (c_parser_gimple_if_stmt): Check for empty labels.
>
>