Friday, February 11, 2011

How to simulate a Delphi breakpoint in code?

I am pretty sure I have seen this before, but I haven't found out / remembered how to do it. I want to have a line of code that when executed from the Delphi debugger I want the debugger to pop-up like there was a break point on that line.

Something like:

FooBar := Foo(Bar);
SimulateBreakPoint; // Cause break point to occur in Delphi IDE if attached
WriteLn('Value: ' + FooBar);

Hopefully that makes sense. I know I could use an exception, but that would be a lot more overhead then I want. It is for some demonstration code.

Thanks in advance!

  • To trigger the debugger from code (supposedly, I don't have a copy of delphi handy to try):

    asm int 3 end;
    

    See this page:

    http://17slon.com/blogs/gabr/2008/03/debugging-with-lazy-breakpoints.html

    Jim McKeeth : That was it. Worked great! Thanks! Now I need to find a way to move up the call stack for the break point. . . .
    Gamecat : Beware to catch EExternal else there will be an external exception while running outside of the debugger.
    gabr : Or, as I suggested: if DebugHook <> 0 then asm int 3 end;
    Osama ALASSIRY : I'd usually do "if (DebugHook <> 0) and (**Break Condition**) then asm int 3 end;" so i'd add a condition to break, and put this code right before an error/bug in some conditions.
  • As Andreas Hausladen stated in comments to that artice, Win32 API DebugBreak() function is less DOS-ish and works equally well.

    Jim McKeeth : DebugBreak() puts the break point in the dissassembly/CPU window. I'd rather have it in my code.
    From gabr

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