[Dwarf-discuss] Re: Dwarf2 Beginner's Question: Pointer variable tracking with Optimization

[Michael Eager]

Any DWARF question is appropriate for the mailing list.

Koji Noguchi wrote:
  > Dear Mailing List Members,
> 
> 
> Hi.  I am implementing a simple code/process migration system
> and was wondering if I can use this DWARF2 debug format to solve my problem.
> 
> The problem is, when I decide to migrate the process, I want to know 
> all the (potential) locations of the pointers on the stack and the registers.
> Input is a C code without type casting, union, pointer arithmetic, etc.
> 
> Does DWARF2 provide enough information for this purpose?
> (I'm using gcc with -O3 -g option).
> 
> I think this is not possible, but I wanted to ask you before I 
> completely give up.
> 
> 
> To show how beginner I am, 
> I tried the following simple code but couldn't figure out the 
> register for pointer 'p_int' from the DWARF2 output.
> 
> @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
> #include <stdio.h>
> #include <stdlib.h>
> 
> int main()
> {
>   int aaa,bbb;
>   int * p_int;
> 
>   aaa = 11;
>   bbb = 22;
>   p_int = &bbb;
> 
>   printf( "aaa = %d bbb = %d p_int = %p *p_int = %d\n",
>           aaa, bbb, p_int, *p_int);
>   return 0;
> }
> 
> 
>   .long .LASF46 # DW_AT_name: "p_int"
>   .byte 0x1 # DW_AT_decl_file
>   .byte 0x8 # DW_AT_decl_line
>   .long 0x2f3 # DW_AT_type
>   .byte 0x0 # end of children of DIE 0x2b4
>   .uleb128 0x5  # (DIE (0x2f3) DW_TAG_pointer_type)
>   .byte 0x4 # DW_AT_byte_size
>   .long 0x4f  # DW_AT_type
>   .byte 0x0 # end of children of DIE 0xb
> 
> @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
> 
> I thought the output would contain "DW_AT_location" info somewhere, 
> but I couldn't find it. Am I missing something?
> 
> Any suggestions would be greatly appreciated
> 
> Thank you.
> 
> Koji Noguchi
> 
> 
> 


-- 
Michael Eager	 eager at eagercon.com
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