Understanding GDB frames

Maxim Grigoriev
2007-05-21T22:24:22Z

I experience some difficulties in finding a precise definition
of gdb frames.

Any help on choosing the right answer among the list provided
by me at the end of this message will be highly appreciated.

QUESTION
========

The program (frame.c) is

#include <stdio.h>

int frame_number = 1;

int f11(int b)
{
int a;

printf("f11() frame number %d\n", frame_number++);

a = b + 1;
b--;
if (b != 0)
{
printf("f11() will be called recursively\n");
f11(b);
}
return a; /* <-- BP set here. */
}

int f1(int a)
{
return f11(a);
}

int main()
{
int a = 1;
int i;

for (i = 0; i <2; i++)
a = f11(a);

a = f11(1);
a = f1(1);

return 0;
}

The gdb command file "CMD":

break frame.c:18
run
continue
continue
continue
continue
kill
quit

was used to run a gdb session like this :
gdb <executable> --command=CMD

Let's define that "frames A and B are the same" if

frame_id_eq ( A->this_id, B->this_id ) == true

The breakpoit has been set at line 18 and hit 5 times.
Execution control has been subsequently taken by
gdb in five frames numbered 1, 2, 3, 4, and 5.

According to the definition of GDB frames,
which statement is correct ?

ANSWERS
=======

1) All frames 1, 2, 3, 4, and 5 are the same;
2) All frames 1, 2, 3, 4, and 5 are different from each other;
3) Frames 1,2, and 4 are the same. Frames 3 and 5 are
different from 1, 2, 4 and from each other;
4) It's implementation-dependent. While doing architecture ports,
people decide how to implement frame_id-related functions
to compare frames;
5) Other ( explanation would be appreciated ).

-- Maxim