Re: [PATCH 1/2] v3: C++: more location wrapper nodes (PR c++/43064, PR c++/43486)

[Jason Merrill <jason@redhat.com>]

On 12/7/18 3:13 PM, David Malcolm wrote:
> On Tue, 2018-12-04 at 18:31 -0500, Jason Merrill wrote:
>> On 12/3/18 5:10 PM, Jeff Law wrote:
>>> On 11/19/18 9:51 AM, David Malcolm wrote:
> [...]
>>> @@ -1058,6 +1058,9 @@ grokbitfield (const cp_declarator
>>> *declarator,
>>>         return NULL_TREE;
>>>       }
>>>   
>>> +  if (width)
>>> +    STRIP_ANY_LOCATION_WRAPPER (width);
>>
>> Why is this needed?  We should already be reducing width to an
>> unwrapped
>> constant value somewhere along the line.
> 
> "width" is coming from cp_parser_member_declaration, from:
> 
> 	      /* Get the width of the bitfield.  */
> 	      width = cp_parser_constant_expression (parser, false, NULL,
> 						     cxx_dialect >= cxx11);
> 
> and currently nothing is unwrapping the value.  We presumably need to
> unwrap (or fold?) it before it is stashed in
>    DECL_BIT_FIELD_REPRESENTATIVE (value).
> 
> Without stripping (or folding) here, we e.g. lose a warning and get this:
>    FAIL: g++.dg/abi/empty22.C  -std=gnu++98  (test for warnings, line 15)

Why does that happen?  check_bitfield_decl ought to handle the location 
wrapper fine.  That's where it gets folded.

>>> @@ -656,6 +656,9 @@ add_capture (tree lambda, tree id, tree
>>> orig_init, bool by_reference_p,
>>>         listmem = make_pack_expansion (member);
>>>         initializer = orig_init;
>>>       }
>>> +
>>> +  STRIP_ANY_LOCATION_WRAPPER (initializer);
>>
>> Why is this needed?  What cares about the tree codes of the capture
>> initializer?
> 
> This is used to populate LAMBDA_EXPR_CAPTURE_LIST.  Without stripping,
> we end up with wrapped VAR_DECLs, rather than the VAR_DECLs themselves,

Sure, that sounds fine.

> and this confuses things later on, for example leading to:
> 
>   PASS -> FAIL : g++.dg/cpp0x/lambda/lambda-type.C  -std=c++14 (test for excess errors)
>   PASS -> FAIL : g++.dg/cpp0x/lambda/lambda-type.C  -std=c++17 (test for excess errors)

Confuses how?

Jason