[Bug c++/14998] GDB cannot handle pointer to member functions being encoded with DW_TAG_ptr_to_member_type

["tromey at redhat dot com" <sourceware-bugzilla@sourceware.org>]

http://sourceware.org/bugzilla/show_bug.cgi?id=14998

--- Comment #8 from Tom Tromey <tromey at redhat dot com> 2013-01-07 19:35:46 UTC ---
(In reply to comment #7)
> The DWARF standard is a bit vague on this:
> 
> "The pointer to member entry has a DW_AT_type attribute to describe the type of
> the class or structure member to which objects of this type may point."
> 
> but it seems like if the DW_AT_type of a pointer-to-member variable "int
> foo::*x;" is simply "int", then the DW_AT_type of a pointer-to-member function
> "int (foo::*x)(float)" would be "int(float)".

I searched the DWARF standard and didn't see anything requiring this.
However, it seems strange to emit the artificial parameter for a method
but not for a pointer-to-method.

If you really don't want to emit it then I think we ought to file a
bug report for the DWARF standard.

> If it works, though, then I'd consider this bug to be lower priority but still
> 'nice to have' (essentially GDB would detect whether the first parameter is
> artificial (& the same type as the DW_AT_containing_type) & if so, use that,
> otherwise insert such a parameter based on the DW_AT_containing_type if that's
> the representation it prefers).
> 
> What are your thoughts on this?

Certainly doable in gdb, but I think it is nicer to agree on a single
standard interpretation and try to avoid this kind of adaptive behavior.

> I guess LINKAGE_NAME is DW_AT_MIPS_linkage_name? Though in any case a function
> pointer won't have a known/fixed name for the function, so I guess it's always
> 'zero'/always displayed?

It seems to be a boolean flag (to my surprise, I didn't actually read
it closely the first time).
There's probably some way to arrange for this to work properly.

Offhand I don't know why it is this way.  It might just be so that people
can tell "what is really going on" -- but a flag would suffice for this.

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