[Bug debug/46955] New: Missing DW_AT_const_value from DW_TAG_template_value_parameter

["dodji at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46955

           Summary: Missing DW_AT_const_value from
                    DW_TAG_template_value_parameter
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: debug
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: dodji@gcc.gnu.org


struct S { int f; };
template<int S::*MP> struct T { };
T<&S::f> v;

For v's type, I just see:

 <2><4f>: Abbrev Number: 6 (DW_TAG_template_value_param)
    <50>   DW_AT_name        : MP       
    <53>   DW_AT_type        : <0x58>   

That is, this parameter has no value.

This is because the DWARF emitter doesn't know how to handle the C++ specific
PTRMEM_CST node that represenst the argument &S::f at that point. That
PTRMEM_CST needs to be folded further into something low level enough for the
DWARF emitter to understand, while keeping its OFFSET_TYPE type meaning it's a
pointer-to-member constant.

This has been first reported in a comment of PR debug/41736, but I am opening
this specific bug for it as I think those two bugs are different.