[Apocalypse]

Hello,

I just started having some very unusual problems with a program I am writing and the Project Builder debugger. For some reason, the program works fine sometimes and crashes other times. I don't know what could be causing this unpredictable behavior (especially when I get different results with identical data). I decided to step through it and see if anything odd happens to data integrity. The only variable I noticed having any particularly odd behavior was "_cmd". I am not sure what this does so if anyone can help me out there I would be much appreciative.

I also had great difficulty using the debugger since the code refused to execute in a linear fashion. Instead, it would jump forward and back a couple lines each time I used the "step-over" command.

I am completely confused so could someone please help shed some light on this problem?

Thanks,
Jeff.

[honeydew]

Originally posted by Apocalypse:
<STRONG>The only variable I noticed having any particularly odd behavior was "_cmd". I am not sure what this does so if anyone can help me out there I would be much appreciative.</STRONG>

<font face = "courier">/Developer/Documentation/Cocoa/ObjectiveC</font>
Object-Oriented Programming and the Objective-C Language, page 91:

When the messaging function finds the procedure that implements a method, it calls the procedure and passes it all the arguments in the message. It also passes the procedure two hidden arguments:

• The receiving object (<font face = "courier">self</font>)
• The selector for the method (<font face = "courier">_cmd</font>)

[lindberg]

Make sure you do a debug build, not a regular build (i.e. the -g option should be passed to cc, and not -O or -O2, which are optimize flags). The compiler can optimize code in very interesting ways, and is totally confusing in the debugger since things seem to execute all out of order, only execute once when you think it should happen multiple times, etc.