[Bug debug/55059] New: DWARF missing concrete class definition

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

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55059

             Bug #: 55059
           Summary: DWARF missing concrete class definition
    Classification: Unclassified
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: debug
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: tromey@gcc.gnu.org


Created attachment 28519
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=28519
test program

This comes from http://sourceware.org/bugzilla/show_bug.cgi?id=14760

I think GCC master from today generates invalid, or at least
questionable, DWARF for the attached test case.
This causes gdb test suite failures.

The bug is in the DWARF for the instantiation of Base.
Current GCC emits:

 <1><f1>: Abbrev Number: 15 (DW_TAG_structure_type)
    <f2>   DW_AT_name        : (indirect string, offset: 0x191): Base<long int,
47, (& a_global), &S::f>    
    <f6>   DW_AT_byte_size   : 1    
    <f7>   DW_AT_decl_file   : 1    
    <f8>   DW_AT_decl_line   : 30    
    <f9>   DW_AT_declaration : 1    
    <f9>   DW_AT_sibling     : <0x155>    

This has DW_AT_declaration -- but there is no concrete instance of the type.

Previous versions of GCC omitted this attribute.  For example, Fedora 16
GCC:

 <1><f1>: Abbrev Number: 10 (DW_TAG_structure_type)
    <f2>   DW_AT_name        : (indirect string, offset: 0x135): Base<long int,
47, (& a_global), &S::f>    
    <f6>   DW_AT_byte_size   : 1    
    <f7>   DW_AT_decl_file   : 1    
    <f8>   DW_AT_decl_line   : 30    
    <f9>   DW_AT_sibling     : <0x155>    

I think the previous approach is preferable.