1

I am trying to get the address of a struct member from debug info using gdb.

My problem is that I have a structure like:

typedef struct{
  int a;
  int b;
  int c;
}tstructDesc;

tstructDesc myStruct =
{
  1,
  2,
  3,
};

int main()
{
  /* Do something */
}

With gdb I can get the address of the myStruct structure with the command "info address myStruct", but I'd like to get the addresses of the member variables (myStruct.a, myStruct.b, myStruct.c). I discovered the "ptype myStruct" command which returns the definition of the struct, from which I can calculate the relative and absolute addresses, but I think it's not an effective way to get the task done.

Do you know any other way to get the addresses of the struct members?

Thanks in advance, Tamas

Tamás Kristóf
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  • Tamas it turns out that tsstructDexc is going to be 3*sizeof(int) so the address of myStruct.a is in fact the address of myStruct. in gdb you can set up a breakpoint and do : (gdb) p &myStruct or (gdb) p &mystruct.a – ForeverStudent Nov 12 '15 at 14:14
  • The solution you give is correct but what you mean with "tsstructDexc is going to be 3*sizeof(int)?". To know the size of a struct you must use sizeof(structname): http://stackoverflow.com/questions/119123/why-isnt-sizeof-for-a-struct-equal-to-the-sum-of-sizeof-of-each-member – terence hill Nov 12 '15 at 14:20

1 Answers1

4

In GDB you can:

(gdb) print myStruct
$1 = {a = 1, b = 2, c = 3}
(gdb) print &myStruct
$2 = (tstructDesc *) 0x600a58 <myStruct>
(gdb) print &myStruct.a
$3 = (int *) 0x600a58 <myStruct>
(gdb) print &myStruct.b
$4 = (int *) 0x600a5c <myStruct+4>
(gdb) print &myStruct.c
$5 = (int *) 0x600a60 <myStruct+8>
terence hill
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