Re: [PATCH] Better error messages for merge-conflict markers (v3)

[Jeff Law <law@redhat.com>]

On 10/30/2015 09:16 AM, David Malcolm wrote:
> This is a rebased version of this patch from back in April:
>    v2: https://gcc.gnu.org/ml/gcc-patches/2015-04/msg00944.html
> which in turn is a rewrite of this one:
>    v1: https://gcc.gnu.org/ml/gcc-patches/2015-03/msg01087.html
>
> The idea is to more gracefully handle merger conflict markers
> in the source code being compiled.  Specifically, in the C and
> C++ frontends, if we're about to emit an error, see if the
> source code is at a merger conflict marker, and if so, emit
> a more specific message, so that the user gets this:
>
> foo.c:1:1: error: source file contains patch conflict marker
>   <<<<<<< HEAD
>   ^
>
> rather than this gobbledegook:
>
> foo.c:1:1: error: expected identifier or '(' before '<<' token
>   <<<<<<< HEAD
>   ^
>
> It's something of a "fit and finish" cosmetic item, but these
> things add up.
>
> Successfully bootstrapped&regrtested on x86_64-pc-linux-gnu;
> adds 82 new PASSes to g++.sum and 27 new PASSes to gcc.sum.
>
> OK for trunk?
>
> This implementation works by looking at the token stream, which
> is slightly clunky; an alternative way of doing it would be to directly
> look at the line the error occurs in and to see if it begins with a
> conflict marker.  Would that be preferable?
>
> gcc/c-family/ChangeLog:
> 	* c-common.h (conflict_marker_get_final_tok_kind): New prototype.
> 	* c-lex.c (conflict_marker_get_final_tok_kind): New function.
>
> gcc/c/ChangeLog:
> 	* c-parser.c (struct c_parser): Expand array "tokens_buf" from 2
> 	to 4.
> 	(c_parser_peek_nth_token): New function.
> 	(c_parser_peek_conflict_marker): New function.
> 	(c_parser_error): Detect patch conflict markers and report them as
> 	such.
>
> gcc/cp/ChangeLog:
> 	* parser.c (cp_lexer_peek_conflict_marker): New function.
> 	(cp_parser_error): Detect patch conflict markers and report them
> 	as such.
I'm still having a hard time seeing this one as all that useful.  It's 
not like it's terribly hard to see the <<<<<< HEAD and realize that 
there's a conflict marker mucking things up.

I'm willing to step aside if other folks thing this is really useful and 
want to review the changes.

jeff