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Re: dwarf2 - multiple DW_TAG_variable for global variable
- From: Nenad Vukicevic <nenad at intrepid dot com>
- To: gcc at gcc dot gnu dot org
- Cc: jan dot kratochvil at redhat dot com, Gary Funck <gary at intrepid dot com>
- Date: Sat, 09 Jan 2010 12:39:55 -0800
- Subject: Re: dwarf2 - multiple DW_TAG_variable for global variable
- References: <4B42EB7A.6000107@intrepid.com>
This dwarf code started appearing since this patch:
------------------------------------------------------------------------
r145293 | jakub | 2009-03-30 14:35:03 +0000 (Mon, 30 Mar 2009) | 11 lines
PR debug/39563
* c-decl.c (struct c_binding): Add locus field.
(bind): Add locus argument, set locus field from it.
(pop_scope): For b->nested VAR_DECL or FUNCTION_DECL,
add a DECL_EXTERNAL copy of b->decl to current BLOCK_VARS.
(push_file_scope, pushtag, pushdecl, pushdecl_top_level,
implicitly_declare, undeclared_variable, lookup_label,
declare_label, c_make_fname_decl, c_builtin_function,
c_builtin_function_ext_scope, store_parm_decls_newstyle): Adjust
bind callers.
Jan, can you confirm that this is indeed the correct DWARF that is being generated.
Thank you,
Nenad
On 1/4/10 11:34 PM, Nenad Vukicevic wrote:
I installed gcc-4.5-20091224 snapshot and noticed that for simple
variable declaration
I get two DW_TAG_variable dies in the object file. For example, the
following
code
int xxxxx;
main()
{xxxxx=1;}
generates (with -g -gdwarf2 -O0 switches):
<1><54>: Abbrev Number: 4 (DW_TAG_variable)
<55> DW_AT_name : (indirect string, offset: 0x36): xxxxx
<59> DW_AT_decl_file : 1
<5a> DW_AT_decl_line : 1
<5b> DW_AT_type : <0x4d>
<5f> DW_AT_external : 1
<60> DW_AT_declaration : 1
<1><61>: Abbrev Number: 5 (DW_TAG_variable)
<62> DW_AT_name : (indirect string, offset: 0x36): xxxxx
<66> DW_AT_decl_file : 1
<67> DW_AT_decl_line : 1
<68> DW_AT_type : <0x4d>
<6c> DW_AT_external : 1
<6d> DW_AT_location : 9 byte block: 3 0 0 0 0 0 0 0 0
(DW_OP_addr: 0)
Is the above normal? 4.3.2 compiler generates only one die, the second
one with
DW_AT_location attribute, which is correct.
I also noticed that this example (were variable is not used):
int xxxxx;
main()
{}
generates only one DW_TAG_variable, the one with DW_AT_location,
which again
should be correct.
I ran into this problem by porting some GDB code that uses DWARF2 and
got surprised
to see this change from the previous version of gcc (4.3).
Thanks,
Nenad