[Mesa-dev] [PATCH] glcpp: error on multiple #else directives

[Ian Romanick]

Carl,

Can you look at this patch and Erik's follow-up patch?  You (still) know
the glcpp much better than any of the rest of us.

(Carl is currently out of town, so I know his response will be slow...)

Thanks.

On 09/23/2013 01:35 PM, Erik Faye-Lund wrote:
> The preprocessor currently eats multiple #else directives
> int the same #if(def) ... #endif block. While I haven't been able
> to find anything that explicitly disallows it, it's nonsensical
> and should probably not be allowed.
> 
> Add checks to reject the code.
> ---
> 
> I'm not entirely sure why parser->skip_stack can be NULL after
> _glcpp_parser_skip_stack_change_if, but apparently it is for at
> least one test.
> 
> I'm also not entirely sure if this should be an error or a warning.
> Thoughts?
> 
>  src/glsl/glcpp/glcpp-parse.y                      | 13 ++++++++++++-
>  src/glsl/glcpp/glcpp.h                            |  1 +
>  src/glsl/glcpp/tests/118-multiple-else.c          |  6 ++++++
>  src/glsl/glcpp/tests/118-multiple-else.c.expected |  8 ++++++++
>  4 files changed, 27 insertions(+), 1 deletion(-)
>  create mode 100644 src/glsl/glcpp/tests/118-multiple-else.c
>  create mode 100644 src/glsl/glcpp/tests/118-multiple-else.c.expected
> 
> diff --git a/src/glsl/glcpp/glcpp-parse.y b/src/glsl/glcpp/glcpp-parse.y
> index 6eaa5f9..885c64d 100644
> --- a/src/glsl/glcpp/glcpp-parse.y
> +++ b/src/glsl/glcpp/glcpp-parse.y
> @@ -332,7 +332,17 @@ control_line:
>  		}
>  	}
>  |	HASH_ELSE {
> -		_glcpp_parser_skip_stack_change_if (parser, & @1, "else", 1);
> +		if (parser->skip_stack &&
> +		    parser->skip_stack->has_else)
> +		{
> +			glcpp_error(& @1, parser, "multiple #else");
> +		}
> +		else
> +		{
> +			_glcpp_parser_skip_stack_change_if (parser, & @1, "else", 1);
> +			if (parser->skip_stack)
> +				parser->skip_stack->has_else = true;
> +		}
>  	} NEWLINE
>  |	HASH_ENDIF {
>  		_glcpp_parser_skip_stack_pop (parser, & @1);
> @@ -2012,6 +2022,7 @@ _glcpp_parser_skip_stack_push_if (glcpp_parser_t *parser, YYLTYPE *loc,
>  		node->type = SKIP_TO_ENDIF;
>  	}
>  
> +	node->has_else = false;
>  	node->next = parser->skip_stack;
>  	parser->skip_stack = node;
>  }
> diff --git a/src/glsl/glcpp/glcpp.h b/src/glsl/glcpp/glcpp.h
> index 8aaa551..ccae96c 100644
> --- a/src/glsl/glcpp/glcpp.h
> +++ b/src/glsl/glcpp/glcpp.h
> @@ -153,6 +153,7 @@ typedef enum skip_type {
>  
>  typedef struct skip_node {
>  	skip_type_t type;
> +	bool has_else;
>  	YYLTYPE loc; /* location of the initial #if/#elif/... */
>  	struct skip_node *next;
>  } skip_node_t;
> diff --git a/src/glsl/glcpp/tests/118-multiple-else.c b/src/glsl/glcpp/tests/118-multiple-else.c
> new file mode 100644
> index 0000000..62ad49c
> --- /dev/null
> +++ b/src/glsl/glcpp/tests/118-multiple-else.c
> @@ -0,0 +1,6 @@
> +#if 0
> +#else
> +int foo;
> +#else
> +int bar;
> +#endif
> diff --git a/src/glsl/glcpp/tests/118-multiple-else.c.expected b/src/glsl/glcpp/tests/118-multiple-else.c.expected
> new file mode 100644
> index 0000000..eaec481
> --- /dev/null
> +++ b/src/glsl/glcpp/tests/118-multiple-else.c.expected
> @@ -0,0 +1,8 @@
> +0:4(1): preprocessor error: multiple #else
> +
> +
> +int foo;
> +
> +int bar;
> +
> +
>