[Bug debug/49366] pointer-to-member-function not given value in DW_TAG_template_value_param

[aoliva at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=49366

--- Comment #4 from Alexandre Oliva <aoliva at gcc dot gnu.org> ---
Author: aoliva
Date: Fri Aug 12 07:11:23 2016
New Revision: 239401

URL: https://gcc.gnu.org/viewcvs?rev=239401&root=gcc&view=rev
Log:
[PR49366] emit loc exprs for C++ non-virtual pmf template value parms

We used to emit, in debug information, the values bound to pointer to
member function template parameters only when they were NULL or
virtual member functions, because those can be represented with
DW_AT_const_value.

In order to represent the symbolic pointer to member function
constants for non-virtual member functions, we'd need to be able to
emit relocations for part of DW_AT_const_value, which we don't.  The
more viable alternative is to use DW_AT_location to represent such
values, as slated for inclusion in DWARFv5, according to
<URL:http://www.dwarfstd.org/ShowIssue.php?issue=130412.1>.

With this patch, when we can't emit a DW_AT_const_value, we emit each
"member" of the pointer to member function "record" as a
DW_OP_stack_value DW_OP_piece, as long as the referenced member
function is output in the same translation unit, otherwise we'd get
relocations to external symbols, something to avoid in debug sections.


for  gcc/ChangeLog

        PR debug/49366
        * dwarf2out.c (loc_list_from_tree_1): Expand some CONSTRUCTORs
        in DW_OP_pieces, just enough to handle pointers to member
        functions.
        (gen_remaining_tmpl_value_param_die_attribute): Use a location
        expression on DWARFv5 if a constant value doesn't work.

for  gcc/testsuite/ChangeLog

        PR debug/49366
        * g++.dg/debug/dwarf2/template-params-12.H: New.
        * g++.dg/debug/dwarf2/template-params-12f.C: New.
        * g++.dg/debug/dwarf2/template-params-12g.C: New.
        * g++.dg/debug/dwarf2/template-params-12n.C: New.
        * g++.dg/debug/dwarf2/template-params-12s.C: New.
        * g++.dg/debug/dwarf2/template-params-12u.C: New.
        * g++.dg/debug/dwarf2/template-params-12v.C: New.
        * g++.dg/debug/dwarf2/template-params-12w.C: New.

Added:
    trunk/gcc/testsuite/g++.dg/debug/dwarf2/template-params-12.H
    trunk/gcc/testsuite/g++.dg/debug/dwarf2/template-params-12f.C
    trunk/gcc/testsuite/g++.dg/debug/dwarf2/template-params-12g.C
    trunk/gcc/testsuite/g++.dg/debug/dwarf2/template-params-12n.C
    trunk/gcc/testsuite/g++.dg/debug/dwarf2/template-params-12s.C
    trunk/gcc/testsuite/g++.dg/debug/dwarf2/template-params-12u.C
    trunk/gcc/testsuite/g++.dg/debug/dwarf2/template-params-12v.C
    trunk/gcc/testsuite/g++.dg/debug/dwarf2/template-params-12w.C
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/dwarf2out.c
    trunk/gcc/testsuite/ChangeLog