[Bug debug/58150] New: debug info about definition of enum class not emitted if the declaration was already used in a template

["b.r.longbons at gmail dot com" <gcc-bugzilla@gcc.gnu.org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58150

            Bug ID: 58150
           Summary: debug info about definition of enum class not emitted
                    if the declaration was already used in a template
           Product: gcc
           Version: 4.8.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: debug
          Assignee: unassigned at gcc dot gnu.org
          Reporter: b.r.longbons at gmail dot com

Created attachment 30649
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=30649&action=edit
minimal testcase

If an enum class has a forward declaration and it is used as a class member
(functions seem to be okay), the full debuginfo is not emitted when the
definition appear later in the TU.

This makes debugging practically impossible.

enums are unusual in that they can be fully used even when they have just a
definition.

Tested gcc versions:
g++-4.6 (Debian 4.6.4-2) 4.6.4
g++-4.7 (Debian 4.7.3-4) 4.7.3
g++-4.8 (Debian 4.8.1-8) 4.8.1

Versions before 4.6 did not implement forward declarations of enum classes, so
this bug is primordial.

The relevant part of the debug information looks like:

 <1><34>: Abbrev Number: 3 (DW_TAG_enumeration_type)
    <35>   DW_AT_name        : (indirect string, offset: 0x84): ByteCode
    <39>   DW_AT_enum_class  : 1
    <39>   DW_AT_declaration : 1
    <39>   DW_AT_byte_size   : 1
    <3a>   DW_AT_decl_file   : 1
    <3b>   DW_AT_decl_line   : 3

Whereas clang generates:

 <1><6f>: Abbrev Number: 6 (DW_TAG_enumeration_type)
    <70>   DW_AT_type        : <0x64>
    <74>   DW_AT_enum_class  : 1
    <75>   DW_AT_name        : (indirect string, offset: 0x98): ByteCode
    <79>   DW_AT_byte_size   : 1
    <7a>   DW_AT_decl_file   : 1
    <7b>   DW_AT_decl_line   : 10