How to examine the stack contents

  • version

    1.0.1

  • scope

    Example.

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

  • description

    How to examine the stack contents

  • 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.

XGDB can be used to examine the contents of the stack memory at a given point in time. For example, compile the following code ensuring that debug is enabled (-g):

int add1(int x) {
  return x + 1;
}

int sub1(int x, int y) {
  return add1(x) - add1(y);
}

int main() {
  sub1(6, 3);
  return 0;
}

From within xTIMEcomposer Studio

Create a new debug configuration via Run->debug Configurations->xCORE Applications. Set a breakpoint at the start of add1 then start debugging. Execution will now break when add1 is reached. The contents of the stack can be viewed from the Debug view. Note: Clicking on the previous stack frames in the Debug view causes the Variables view to be updated with the variables in scope for this stack frame.

From the command line

On the command line, stack contents can be displayed using the backtrace command. For example, start XGDB, connect to the simulator and set a breakpoint on add1. When run, execution will break at the start of add1. You can display the stack contents using the backtrace command as follows:

> xgdb a.xe
...etc...
(gdb) connect -s
0xffffc04e in ?? ()
(gdb) b add1
Breakpoint 1 at 0x100b2: file examining_the_stack.xc, line 9.
(gdb) r
...etc...
Breakpoint 1, add1 (x=6) at examining_the_stack.xc:9
9     return x + 1;
(gdb) backtrace
#0  add1 (x=6) at examining_the_stack.xc:9
#1  0x000100ca in sub1 (x=6, y=3) at examining_the_stack.xc:13
#2  0x000100e4 in main () at examining_the_stack.xc:17