Re: [PATCH] c++: modules and std::source_location::current() def arg [PR100881]

[Nathan Sidwell <nathan@acm.org>]

On 12/7/22 16:50, Patrick Palka wrote:
> We currently declare __builtin_source_location with a const void* return
> type instead of the true type (const std::source_location::__impl*), and
> later when folding this builtin we just obtain the true type via name
> lookup.
> 
> But the below testcase demonstrates this name lookup approach seems to
> interact poorly with modules, since we may import an entity that uses
> std::source_location::current() in a default argument (or DMI) without
> also importing <source_location>, and thus the name lookup will fail
> when folding the builtin at the call site unless we also import
> <source_location>.
> 
> This patch fixes by instead initially declaring __builtin_source_location
> with an auto return type and updating it appropriately upon its first use.
> Thus when folding calls to this builtin we can fish out the true return
> type through the type of the CALL_EXPR and avoid needing to do name
> lookup.

That's a clever approach!  LGTM

nathan

-- 
Nathan Sidwell