gdb/doc/stack_frame.txt

   1                   ^    ->|            |
   2 Frame             |   |  |            |
   3 Number          - |   |  |============|       int fact (int n)
   4                |  |   |  |   i = 3    |       {
   5                |  |   |  |------------|         if (0 == n) {
   6                |  |   |  |   f = ?    |           return  1;  <-------- PC
   7   #4 main()   <   |   |  |------------|        }
   8                |  |   |  |            |         else {
   9                |  |  -+->|------------|   --->    return n * fact (n - 1);
  10                |   -+-+--+-----o      |  |      }
  11                 =   | |  |============|  |    }
  12                |    | |  |   n = 3    |  |
  13                |    | |  |------------|  |    main ()
  14   #3 fact (3) <     | |  |     o---------+-   {
  15                |   -+-+->|------------|  | |    int  i;
  16                |  | |  --+-----o      |  | |
  17                 = | |    |============|  | |    for (i = 0; i < 10; i++) {
  18                |  | |    |   n = 2    |  |  ->    int  f = fact (i);
  19                |  | |    |------------|  |        printf ("%d! = %d\n", i , f);
  20   #2 fact (2) <   | |    |     o------+--|      }
  21                |  | |  ->|------------|  |    }
  22                |  |  -+--+-----o      |  |
  23                 = |   |  |============|  |
  24                |  |   |  |   n = 1    |  |
  25                |  |   |  |------------|  |
  26   #1 fact (1) <   |   |  |     o------+--|
  27                |  |   |  |------------|  |
  28                |   ---|--+-----o      |<-+------- FP
  29                 =     |  |============|  |                   |
  30                |      |  |   n = 0    |  |                   |
  31                |      |  |------------|  |                   |
  32   #0 fact (0) <       |  |     o---------                    |
  33                |      |  |------------|                      |
  34                |       --+-----o      |<--------- SP         |
  35                 =        |============|                      |
  36                |         |  Red Zone  |                      v
  37                |         \/\/\/\/\/\/\/                 Direction of
  38   #-1         <          \/\/\/\/\/\/\/                 stack growth
  39                |         |            |