[Bug debug/83550] New: [6/7/8 Regression] Bad location of DW_TAG_structure_type with forward declaration since r224161

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83550

            Bug ID: 83550
           Summary: [6/7/8 Regression] Bad location of
                    DW_TAG_structure_type with forward declaration since
                    r224161
           Product: gcc
           Version: 7.2.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: debug
          Assignee: unassigned at gcc dot gnu.org
          Reporter: jakub at gcc dot gnu.org
  Target Milestone: ---

Starting with r224161 we get different DW_AT_decl_line on DW_TAG_structure_type
with a forward declaration:
struct S;
extern struct S s;
struct S { int a, b; };
struct S q;

Previously we did get line 3, i.e. the definition, now we get line 1, i.e. the
forward declaration.