[binutils-gdb] dwarf: use find_abstract_instance for vars and DW_AT_specification

[binutils-gdb] dwarf: use find_abstract_instance for vars and DW_AT_specification

[Martin Liska]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=06ce017c7d73f90db1c99f9e6a56c486b0313864

commit 06ce017c7d73f90db1c99f9e6a56c486b0313864
Author: Martin Liska <mliska@suse.cz>
Date:   Wed Aug 3 22:31:09 2022 +0200

    dwarf: use find_abstract_instance for vars and DW_AT_specification
    
    The following simple test case fails when dwz is used:
    
    $ cat demo.C
    namespace std {
      enum { _S_fixed, _S_floatfield = _S_fixed };
      struct {
        struct {};
      }
      __ioinit;
    }
    
    int main() {
      return 0;
    }
    
    $ g++ demo.C -g && cp a.out b.out && dwz -m xxx.so a.out b.out && objdump -S a.out >/dev/null
    objdump: DWARF error: could not find variable specification at offset 0x3d3
    
    As seen the reference is defined in xxx.so shared part:
    
    $ eu-readelf -w -N a.out | grep -A3 -B3 3d3
                 decl_column          (data1) 11
                 sibling              (ref_udata) [   387]
     [   387]    variable             abbrev: 30
                 specification        (GNU_ref_alt) [   3d3]
                 location             (exprloc)
                  [ 0] addr 0x404019
     [   396]    subprogram           abbrev: 32
    
    $ eu-readelf -w -N a.out | less
    
    ...
    
     Compilation unit at offset 920:
     Version: 5, Abbreviation section offset: 0, Address size: 8, Offset size: 4
     Unit type: partial (3)
    ...
     [   3d3]      variable             abbrev: 31
                   name                 (strp) "__ioinit"
                   decl_file            (data1) demo.C (10)
                   decl_line            (data1) 6
                   decl_column          (data1) 3
                   type                 (ref_udata) [   3c4]
                   declaration          (flag_present) yes
    
    With the patch the same output is emitted as before usage of dwz.
    
    bfd/ChangeLog:
    
            PR 29442
            * dwarf2.c (struct varinfo): Use const char * type.
            (scan_unit_for_symbols): Call find_abstract_instance for
            DW_AT_specification for variables that can be in a different CU
            (e.g. done by dwz)

Diff:
---
 bfd/dwarf2.c | 22 +++++++---------------
 1 file changed, 7 insertions(+), 15 deletions(-)

diff --git a/bfd/dwarf2.c b/bfd/dwarf2.c
index 47618788513..fbe9dd2070b 100644
--- a/bfd/dwarf2.c
+++ b/bfd/dwarf2.c
@@ -1801,7 +1801,7 @@ struct varinfo
   /* The type of this variable.  */
   int tag;
   /* The name of the variable, if it has one.  */
-  char *name;
+  const char *name;
   /* The address of the variable.  */
   bfd_vma addr;
   /* Where the symbol is defined.  */
@@ -4094,11 +4094,12 @@ scan_unit_for_symbols (struct comp_unit *unit)
 		case DW_AT_specification:
 		  if (is_int_form (&attr) && attr.u.val)
 		    {
-		      struct varinfo * spec_var;
-
-		      spec_var = lookup_var_by_offset (attr.u.val,
-						       unit->variable_table);
-		      if (spec_var == NULL)
+		      bool is_linkage;
+		      if (!find_abstract_instance (unit, &attr, 0,
+						   &var->name,
+						   &is_linkage,
+						   &var->file,
+						   &var->line))
 			{
 			  _bfd_error_handler (_("DWARF error: could not find "
 						"variable specification "
@@ -4106,15 +4107,6 @@ scan_unit_for_symbols (struct comp_unit *unit)
 					      (unsigned long) attr.u.val);
 			  break;
 			}
-
-		      if (var->name == NULL)
-			var->name = spec_var->name;
-		      if (var->file == NULL && spec_var->file != NULL)
-			var->file = strdup (spec_var->file);
-		      if (var->line == 0)
-			var->line = spec_var->line;
-		      if (var->sec == NULL)
-			var->sec = spec_var->sec;
 		    }
 		  break;