[Bug c++/65108] New: Missing DWARF info for static const class members

["wingo at igalia dot com" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65108

            Bug ID: 65108
           Summary: Missing DWARF info for static const class members
           Product: gcc
           Version: 4.9.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: wingo at igalia dot com

Compiling the following C++ program does not residualize DWARF info for
Foo::one, but does for Bar::two, even though Foo::one is used and Bar::two is
not.

$ cat <<END > foo.cc
class Foo {
public:
  static const int one = 1;
};

namespace Bar {
  static const int two = 2;
}

int main (int argc, char* argv[])
{
  return Foo::one;
}
END
$ g++ --version | head -1
g++ (Debian 4.9.2-10) 4.9.2
$ g++ -Wall -g -O0 foo.cc
$ objdump --dwarf=info a.out

a.out:     file format elf64-x86-64

Contents of the .debug_info section:

  Compilation Unit @ offset 0x0:
   Length:        0xaa (32-bit)
   Version:       4
   Abbrev Offset: 0x0
   Pointer Size:  8
 <0><b>: Abbrev Number: 1 (DW_TAG_compile_unit)
    <c>   DW_AT_producer    : (indirect string, offset: 0x1b): GNU C++ 4.9.2
-mtune=generic -march=x86-64 -g -O0
    <10>   DW_AT_language    : 4    (C++)
    <11>   DW_AT_name        : (indirect string, offset: 0x0): /tmp/foo.cc
    <15>   DW_AT_low_pc      : 0x400576
    <1d>   DW_AT_high_pc     : 0x12
    <25>   DW_AT_stmt_list   : 0x0
 <1><29>: Abbrev Number: 2 (DW_TAG_const_type)
    <2a>   DW_AT_type        : <0x2e>
 <1><2e>: Abbrev Number: 3 (DW_TAG_base_type)
    <2f>   DW_AT_byte_size   : 4
    <30>   DW_AT_encoding    : 5    (signed)
    <31>   DW_AT_name        : int
 <1><35>: Abbrev Number: 4 (DW_TAG_subprogram)
    <36>   DW_AT_external    : 1
    <36>   DW_AT_name        : (indirect string, offset: 0x16): main
    <3a>   DW_AT_decl_file   : 1
    <3b>   DW_AT_decl_line   : 10
    <3c>   DW_AT_type        : <0x2e>
    <40>   DW_AT_low_pc      : 0x400576
    <48>   DW_AT_high_pc     : 0x12
    <50>   DW_AT_frame_base  : 1 byte block: 9c     (DW_OP_call_frame_cfa)
    <52>   DW_AT_GNU_all_call_sites: 1
    <52>   DW_AT_sibling     : <0x73>
 <2><56>: Abbrev Number: 5 (DW_TAG_formal_parameter)
    <57>   DW_AT_name        : (indirect string, offset: 0xc): argc
    <5b>   DW_AT_decl_file   : 1
    <5c>   DW_AT_decl_line   : 10
    <5d>   DW_AT_type        : <0x2e>
    <61>   DW_AT_location    : 2 byte block: 91 6c     (DW_OP_fbreg: -20)
 <2><64>: Abbrev Number: 5 (DW_TAG_formal_parameter)
    <65>   DW_AT_name        : (indirect string, offset: 0x4d): argv
    <69>   DW_AT_decl_file   : 1
    <6a>   DW_AT_decl_line   : 10
    <6b>   DW_AT_type        : <0x73>
    <6f>   DW_AT_location    : 2 byte block: 91 60     (DW_OP_fbreg: -32)
 <2><72>: Abbrev Number: 0
 <1><73>: Abbrev Number: 6 (DW_TAG_pointer_type)
    <74>   DW_AT_byte_size   : 8
    <75>   DW_AT_type        : <0x79>
 <1><79>: Abbrev Number: 6 (DW_TAG_pointer_type)
    <7a>   DW_AT_byte_size   : 8
    <7b>   DW_AT_type        : <0x7f>
 <1><7f>: Abbrev Number: 7 (DW_TAG_base_type)
    <80>   DW_AT_byte_size   : 1
    <81>   DW_AT_encoding    : 6    (signed char)
    <82>   DW_AT_name        : (indirect string, offset: 0x11): char
 <1><86>: Abbrev Number: 8 (DW_TAG_namespace)
    <87>   DW_AT_name        : Bar
    <8b>   DW_AT_decl_file   : 1
    <8c>   DW_AT_decl_line   : 6
    <8d>   DW_AT_sibling     : <0x9e>
 <2><91>: Abbrev Number: 9 (DW_TAG_variable)
    <92>   DW_AT_name        : two
    <96>   DW_AT_decl_file   : 1
    <97>   DW_AT_decl_line   : 7
    <98>   DW_AT_type        : <0x29>
    <9c>   DW_AT_declaration : 1
    <9c>   DW_AT_const_value : 2
 <2><9d>: Abbrev Number: 0
 <1><9e>: Abbrev Number: 10 (DW_TAG_variable)
    <9f>   DW_AT_specification: <0x91>
    <a3>   DW_AT_location    : 9 byte block: 3 14 6 40 0 0 0 0 0    
(DW_OP_addr: 400614)
 <1><ad>: Abbrev Number: 0

Note the presence of Bar::two, but not Foo::one.

Could be related to bug 56251.  If I instantiate Foo, then Foo::one debuginfo
is indeed serialized, so this problem only manifests itself for classes that
are not designed to be instantiated -- arguably a bad idiom, but not incorrect,
to my limited knowledge.