[Mesa-dev] [PATCH] glsl: empty declarations should be valid

[Paul Berry]

On 4 August 2011 18:18, Chad Versace <chad at chad-versace.us> wrote:
> On 08/04/2011 01:29 PM, Eric Anholt wrote:
>> On Thu,  4 Aug 2011 12:59:35 +0900, Chia-I Wu <olvaffe at gmail.com> wrote:
>>> From: Chia-I Wu <olv at lunarg.com>
>>>
>>> Unlike C++, empty declarations such as
>>>
>>>   float;
>>>
>>> should be valid.  The spec is not explicit about this actually.
>>>
>>> Some apps that generate their shader sources may rely on this.  This was
>>> noted when porting one of them to Linux from Windows.
>>
>> Ew.  Looking the GLSL 1.20 spec, I see:
>>
>> statement:
>>         declaration_statement
>>
>> declaration_statement:
>>         declaration
>>
>> declaration:
>>         init_declarator_list SEMICOLON
>>
>> init_declarator_list:
>>         single_declaration
>>
>> single_declaration:
>>         fully_specified_type
>>         fully_specified_type IDENTIFIER
>>
>> so it looks like that is actually valid code.  That's awful.
>
> I first suspected that this was a spec grammar bug. But it is still present in
> the GLSL 4.10 spec, so it's unlikely to be a bug.
>
> Surprisingly, C also allows empty declarations. Compiling this
>    float;
>    int main() { return 0; }
> with `gcc --std=c99` succeeds and emits this warning:
>     warning: useless type name in empty declaration [enabled by default]
>
> I hate to say this, but I believe the spec grammar intentionally allows empty
> declarations. C allows it, and GLSL tries to mimic C.
>
> Even though I don't like empty declarations, this patch is
> Reviewed-by: Chad Versace <chad at chad-versace.us>
>
> --
> Chad Versace
> chad at chad-versace.us
>
>
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>
>

Anyone want to volunteer to write a Piglit test for this?  It seems
like the kind of obscure corner case that we're likely to regress on
if we don't explicitly test for it.