Unhandled Exception Error

[teddybouch]

I am resurrecting old code from a few years ago, and I unfortunately have little documentation as to how it was compiled and what environment it was built in. At this point, I have successfully gotten it to build, but there are errors at execution, specifically an unhandled exception error on a memory access. The error text is:

Unhandled exception at 0x0002cb80 in Lab4_2008.exe: 0xC0000005: Access violation reading location 0x0002cb80.

It is always the same memory address that is the location, and when I break out of the program it takes me to the following function:

UINT   
CHapticThread::GetClosestPossiblePeriod(UINT period)
{
    TIMECAPS    timecaps;
    MMRESULT    mmRes;

    mmRes = ::timeGetDevCaps( &timecaps, sizeof(TIMECAPS) );
    assert(mmRes == TIMERR_NOERROR);

    if ( period < timecaps.wPeriodMin )
        return timecaps.wPeriodMin;

    if ( period > timecaps.wPeriodMax )
        return timecaps.wPeriodMax;

    return period;
}

Specifically, it's the call to timeGetDevCaps that is where the error occurs. I don't pretend to know all the intricacies of how pointers work - I am a mechanical engineer who has picked up some programming. However, that's the only thing that I can think of because of the association with an address. Any suggestions?

[Sci@phy]

well, show us your timeGetDevCaps function for start :)

[Salem]

I think it's just this.
http://msdn.microsoft.com/en-us/library/ms713416.aspx

But the execution address and the read address being the same seems kinda odd to me.

If that really is the case, then the code took a flying jump off a cliff (typically, following an uninitialised function pointer). The "stack" at that point is pretty much meaningless, so I wouldn't put too much store in that.

Putting a breakpoint at the call, then trying "step over" would give more concrete information as to whether this was the cause, or merely the last bit of salvageable stack from the disaster which follows.

[teddybouch]

Sorry, you lost me on the execution address and the read address being the same. The attempted read address is repeated twice, if that's what you are referring to, but that's what happened everywhere else I saw the error.

Salem is correct - the timeGetDevCaps function is a part of the winmm.lib file, which means that I can't see the code and don't know how the constructor initializes everything.

[Salem]

The same means this:
Unhandled exception at 0x0002cb80 in Lab4_2008.exe: 0xC0000005: Access violation reading location 0x0002cb80.

But did you do as I suggest, put a breakpoint on mmRes = ::timeGetDevCaps( &timecaps, sizeof(TIMECAPS) ); then step over it?

It that works, then the problem is somewhere else.

[stilllearning]

Well I tried putting your stuff in a standalone program and it works without any difficulties.

It is possible that you have code elsewhere which is corrupting your stack, and the problem shows up when you call timeGetDevCaps. Have you considered running your code through a memory checking tool ?

[Salem]

> Well I tried putting your stuff in a standalone program and it works without any difficulties.
Yeah, tests like that pretty much nail the "it's a bug elsewhere" argument.