How to automate the repetition of XGDB commands

• version

  1.0.1

• scope

  Example.

  This code is provided as example code for a user to base their code on.

• description

  How to automate the repetition of XGDB commands

• boards

  Unless otherwise specified, this example runs on the SliceKIT Core Board, but can easily be run on any XMOS device by using a different XN file.

Sometimes it is useful to be able to repeat a sequence of XGDB commands a number of times. For example, in order to better understand the reason why a program traps, it might be instructive to ‘single step’ your way to the trap instead of just continuing. This might give us an indication of the route taken leading up to the trap. As a simple example of using this mechanism, compile the following code ensuring that debug is enabled (-g):

int main() {
  int i, j = 0;
  for (i = 0; i < 5; ++i) {
    j += i;
  }
  return 0;
}

For example, start XGDB, connect to the simulator, set a breakpoint on main and start debugging. Execution will now break when main is reached. The following example tells XGDB to single step while i < 5, and on each step, print the value of the loop index i:

> xgdb a.xe
...etc...
(gdb) connect -s
0xffffc070 in ?? ()
(gdb) b main
Breakpoint 1 at 0x100b0: file repeating_commands_interactively.xc, line 13.
(gdb) run
...etc...
Breakpoint 1, main () at repeating_commands_interactively.xc:13
13    int i, j = 0;
(gdb) while i < 5
 >step
 >print i
 >end
14    for (i = 0; i < 5; ++i) {
$1 = -1159860211
15      j += i;
$2 = 0
14    for (i = 0; i < 5; ++i) {
$3 = 0
15      j += i;
$4 = 1
14    for (i = 0; i < 5; ++i) {
$5 = 1
15      j += i;
$6 = 2
14    for (i = 0; i < 5; ++i) {
$7 = 2
15      j += i;
$8 = 3
14    for (i = 0; i < 5; ++i) {
$9 = 3
15      j += i;
$10 = 4
14    for (i = 0; i < 5; ++i) {
$11 = 4
17    return 0;
$12 = 5
(gdb)