[PATCH] D68117: [DWARF-5] Support for C++11 defaulted, deleted member functions.

[David Blaikie via Phabricator via cfe-commits]

dblaikie added a comment.

In D68117#1707578 <https://reviews.llvm.org/D68117#1707578>, @SouraVX wrote:

> In D68117#1702595 <https://reviews.llvm.org/D68117#1702595>, @probinson wrote:
>
> > We really do want to pack the four mutually exclusive cases into two bits.  I have tried to give more explicit comments inline to explain how you would do this.  It really should work fine, recognizing that the "not defaulted" case is not explicitly represented in the textual IR because it uses a zero value in the defaulted/deleted subfield of SPFlags.
>
>
> Thanks Paul, for suggesting this. Your approach works fine. But as I was working on some lvm-dwarfdump test cases. We seems to miss one corner case --
>  Consider this test case;
>  class foo{
>
>   foo() = default;
>   ~foo() = default;
>    void not_special() {}
>
> };
>  void not_a_member_of_foo(){}
>
> Now I'm getting DW_AT_defaulted getting emitted with value DW_DEFAULTED_no, for functions "not_special" and "not_a_member_of_foo". This behavior is undesirable since, DW_AT_defaulted attributes is only valid for C++ special member functions{Constructors/Destructors, ...}.
>
> Please correct me if I'm wrong -- Now This attributes to- implicitly defined "0" NotDefaulted bit.  which is getting checked{that's fine as long as we have a dedicated bits for distinguishing} and true for every subprogram or function in a CU.
>  void DwarfUnit::applySubprogramAttributes( ...
>  ...
>  else if (SP->isNotDefaulted())
>
>   addUInt(SPDie, dwarf::DW_AT_defaulted, dwarf::DW_FORM_data1,
>           dwarf::DW_DEFAULTED_no);
>
> ...


Perhaps we should only emit DEFAULTED_yes, and assume anything that's not DEFAULTED_yes, is... not defaulted?

Also: What features is anyone planning to build with this information? I'm sort of inclined not to implement features without some use-case in mind/planned.


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