[Dwarf-discuss] Debug info generation (target: Fr30) - GCC 4.1.1

[Rohit Arul Raj]

Hi all,

I need some clarification regarding the debug info generated for
var_arg function.

Target: fr30
Compiler version : v4.1.1
binutils              : v2.16
newlib               : v1.14.0

<<<<<<<<<<    SAMPLE TEST PROGRAM   >>>>>>>>>>>>

#include <stdio.h>
int fun(const char *name,...)
{
  return 9;
}

int main()
{
  fun("Rohit",4,5,6,7);
  return 0;
}


<<<<<<<<<<<<        OBJDUMP           >>>>>>>>>>>>>>>

00010110 <fun>:
#include <stdio.h>

/* Variadic function */
int fun(const char *name,...)
{
   10110:	17 07       	st r7, at -r15               // value 6
   10112:	17 06       	st r6, at -r15               // value 5
   10114:	17 05       	st r5, at -r15               // value 4
   10116:	17 04       	st r4, at -r15               // contents of name
   10118:	0f 01       	enter 0x4
  return 9;
   1011a:	c0 91       	ldi:8 0x9,r1
}
   1011c:	8b 14       	mov r1,r4
   1011e:	07 0e       	ld @r15+,r14
   10120:	a3 04       	addsp 16
   10122:	97 20       	ret

00010124 <main>:

int main()
{
   10124:	17 81       	st rp, at -r15
   10126:	0f 02       	enter 0x8
  fun("Rohit",4,5,6,7);
   10128:	c0 71       	ldi:8 0x7,r1
   1012a:	14 f1       	st r1, at r15
   1012c:	9f 84 00 01 	ldi:32 0x10f60,r4
   10130:	0f 60
   10132:	c0 45       	ldi:8 0x4,r5
   10134:	c0 56       	ldi:8 0x5,r6
   10136:	c0 67       	ldi:8 0x6,r7
   10138:	9f 81 00 01 	ldi:32 0x10110,r1
   1013c:	01 10
   1013e:	97 11       	call @r1
  return 0;
   10140:	c0 01       	ldi:8 0x0,r1

}
   10142:	8b 14       	mov r1,r4
   10144:	9f 90       	leave
   10146:	07 81       	ld @r15+,rp
   10148:	97 20       	ret
	...
<<<<<<<<<<<<<<        READELF DUMP     >>>>>>>>>>>>>>>

1><fb>: Abbrev Number: 6 (DW_TAG_subprogram)
  <fc>     DW_AT_sibling     : <129>	
  <100>     DW_AT_external    : 1	
  <101>     DW_AT_name        : fun	
  <105>     DW_AT_decl_file   : 10	
  <106>     DW_AT_decl_line   : 5	
  <107>     DW_AT_prototyped  : 1	
  <108>     DW_AT_type        : <4b>	
  <10c>     DW_AT_low_pc      : 0x10110	
  <110>     DW_AT_high_pc     : 0x10124	
  <114>     DW_AT_frame_base  : 0	(location list)

 <2><118>: Abbrev Number: 7 (DW_TAG_formal_parameter)
  <119>     DW_AT_name        : name	
  <11e>     DW_AT_decl_file   : 10	
  <11f>     DW_AT_decl_line   : 4	
  <120>     DW_AT_type        : <b1>	
  <124>     DW_AT_location    : 2 byte block: 91 0 	(DW_OP_fbreg: 0)

<debug_loc section>
Offset   Begin    End      Expression
    00000000 00010110 00010112 (DW_OP_reg15)
    00000000 00010112 00010114 (DW_OP_breg15: 4)
    00000000 00010114 00010116 (DW_OP_breg15: 8)
    00000000 00010116 00010118 (DW_OP_breg15: 12)
    00000000 00010118 0001011a (DW_OP_breg15: 16)
    00000000 0001011a 00010124 (DW_OP_breg14: 20)

>From the readelf output, the location information for variable "name"
is generated by location lists.
For address range 0x00010110 - 0x00010112, the expression for variable
"name" is in terms of stack pointer.But at that instant, the stack
pointer contains the value 7.

For address range 0x00010118 - 0x0001011a, the expression is set as SP
+ 16, when it should have been SP + 0.

1. Have i overseen any details while interpreting the debug info?
2. Is the compiler generating proper debug info?

Regards,
Rohit