[cfe-dev] CXX11 attribute spelling and LateParsed=1

[Eric Fiselier via cfe-dev]

On Mon, Oct 9, 2017 at 7:47 PM, Richard Smith via cfe-dev <
cfe-dev at lists.llvm.org> wrote:

> On 6 October 2017 at 07:36, Javier López Gómez via cfe-dev <
> cfe-dev at lists.llvm.org> wrote:
>
>> Hi,
>>
>> I'm new to Clang hacking. Recently -prior to addition of a new
>> attribute-, I tried adding a C++11 spelling of the DiagnoseIf attribute in
>> the file
>> `tools/clang/include/clang/Basic/Attr.td':
>>
>>   let Spellings = [GNU<"diagnose_if">,
>>                    CXX11<"", "diagnose_if", 201603>];
>>
>> but the parser complains if the expression contains references to
>> function arguments, even if `LateParsed = 1' is specified, i.e. this
>> works
>>
>>   int foo(int arg) __attribute__((diagnose_if(arg == 0, "text",
>> "warning")));
>>
>> but this will not:
>>
>>   [[diagnose_if(arg == 0, "text", "warning")]] int foo(int arg);
>>
>>
>> Am I missing something? Any help will be much appreciated.
>
>
> There is nowhere that a C++11-syntax attribute can be written where it
> appertains to the function entity and the function parameter names are in
> scope. The two locations where attributes can be applied to a name
> introduced by a declarator are:
>
>   [[here]] int f [[and_here]] (int x);
>
> ... and neither of them follows the "x" parameter's declaration. After
> some discussion with Aaron, we think the best way forward is to recast such
> attributes as attributes on the function *type* (that perhaps don't change
> the canonical type, but do affect how the function declarator is
> interpreted as forming a function in some way). That'd mean you'd put the
> attributes:
>
>   int f(int x) [[here]];
>
> ... which conveniently is a place where the function parameters are in
> scope. The downside is that we don't have parsing support for attributes
> that appertain to function types yet. That would need to be added.
>

I've been working on a fix for this; But if you want to hack on this, I'm
happy to yield.


>
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