What is a single step exception?

Question

What is a single step exception? In the context of a stack trace and a break point?

Cheers, J

Answer 1

This exception usually is a trap (a kind of exception, which itself is a kind of interrupt) that is raised by the CPU.

A common debugging scenario is:

1. Breakpoint is hit
2. User asks the debugger to "single step" exactly one line of code
3. line of code is executed
4. CPU raises single step execution (exception code 1)
5. Debugger catches single step exception (and usually nicely handles this by highlighting the next line and updating variable watches)

However, this exception can also be raised in other cases. You can refer to http://support.microsoft.com/kb/117389 as a starting point.