[RFA] PR c++/39637

[Mark Mitchell]

Dodji Seketeli wrote:

> In this PR, we crash (on assert) in dependent_type_p(type), called by
> cxx_sizeof_or_alignof_type because the former function expects the
> processing_template_decl flag to be set when TYPE is a TEMPLATE_TYPE_PARM.
> 
> Using the more robust function uses_template_params instead of dependent_type_p
> seems to address the issue.

I consider almost all uses of uses_template_params to be a bug.  It's an
ill-defined function which involves walking around the tree recursively.
 In contrast, dependent_type_p is supposed to implement a well-defined
concept from the standard.

If we're in a context where we might be looking at template parameters,
processing_template_decl should be set.  Without more information, it's
hard to figure out where that should have happened.

Thanks,

-- 
Mark Mitchell
CodeSourcery
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