[Bug debug/39524] New: Duplicite C++ DW_TAG_variable breaking its DW_AT_location resolution

[jan dot kratochvil at redhat dot com]

Tested on: GNU C++ 4.4.0 20090323 (experimental)    

Testcase:
------------------------------------------------------------------------------
namespace A
  {
    static int var2 = 2;
  }

int
func (void)
{
  using A::var2;

  return var2;
}
------------------------------------------------------------------------------
will generate (reduced):

 <1><2d>: Abbrev Number: 2 (DW_TAG_subprogram)
    <2f>   DW_AT_name        : (indirect string, offset: 0x42): func    
    <3d>   DW_AT_low_pc      : 0x0      
    <45>   DW_AT_high_pc     : 0xc      
    <4d>   DW_AT_frame_base  : 0x0      (location list)
 <2><55>: Abbrev Number: 3 (DW_TAG_lexical_block)
    <56>   DW_AT_low_pc      : 0x4      
    <5e>   DW_AT_high_pc     : 0xa      
 <3><66>: Abbrev Number: 4 (DW_TAG_imported_declaration)
    <69>   DW_AT_import      : <0x7f>   [Abbrev Number: 7 (DW_TAG_variable)]
 <1><76>: Abbrev Number: 6 (DW_TAG_namespace)
    <77>   DW_AT_name        : A        
 <2><7f>: Abbrev Number: 7 (DW_TAG_variable)
    <80>   DW_AT_name        : (indirect string, offset: 0x34): var2    
    <84>   DW_AT_decl_file   : 1        
    <85>   DW_AT_decl_line   : 3        
    <86>   DW_AT_type        : <0x6f>   
    <8a>   DW_AT_declaration : 1        
 <2><8b>: Abbrev Number: 7 (DW_TAG_variable)
    <8c>   DW_AT_name        : (indirect string, offset: 0x34): var2    
    <84>   DW_AT_decl_file   : 1        
    <85>   DW_AT_decl_line   : 3        
    <92>   DW_AT_type        : <0x6f>   
    <96>   DW_AT_declaration : 1        
 <1><98>: Abbrev Number: 8 (DW_TAG_variable)
    <99>   DW_AT_specification: <0x8b>  
    <9d>   DW_AT_location    : 9 byte block: 3 0 0 0 0 0 0 0 0  (DW_OP_addr: 0)

You can see the code references the <7f> "var" instance but DW_AT_location is
given by the <98> completion only for the <8b> "var" instance.

Also <7f> and <8b> have a name conflict as being in the same naming scope.

This problem causes a wrong evaluation by Archer archer-keiths-expr-cumulative
branch (which is IMO right) for the more complex testcase - as it cannot find
the right DW_AT_location there:
------------------------------------------------------------------------------
# archer-keiths-expr-cumulative=35ca449e9f1a4cd477df644f717bbe4e3362c486/gdb -q
./outer
(gdb) l 1
1       #include <stdlib.h>
2
3       namespace A
4         {
5           static int var = 2;
6         }
7
8       int
9       main (void)
10      {
11        int var = 1;
12      
13        if (var != 1)         /* var-is-1 */
14          abort ();
15      
16        {
17          using A::var;
18      
19          if (var != 2)       /* var-is-2 */
20            abort ();
21        }
22      
23        return 0;             /* break-here */
24      }
(gdb) b 13
Breakpoint 1 at 0x4005a7: file outer.C, line 13.
(gdb) r
Starting program: /tmp/outer 

Breakpoint 1, main () at outer.C:13
13        if (var != 1)         /* var-is-1 */
(gdb) p var
$1 = 1
(gdb) adv 19
main () at outer.C:19
19          if (var != 2)       /* var-is-2 */
(gdb) p var
$2 = 1
^^^^^^ Wrong GDB evaluation.
(gdb) adv 23
main () at outer.C:23
23        return 0;             /* break-here */
(gdb) q
------------------------------------------------------------------------------


-- 
           Summary: Duplicite C++ DW_TAG_variable breaking its
                    DW_AT_location resolution
           Product: gcc
           Version: 4.4.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: debug
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: jan dot kratochvil at redhat dot com
GCC target triplet: x86_64-unknown-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39524