Why does a pointer change itself during function transition?

Question

In the following case I'm calling a Func with pointer passed to it, but in the called function, the parameter shows the pointer value as something totally bogus. Something like below.

bool flag = Func(pfspara);--> pfspara = 0x0091d910 

bool Func(PFSPARA pfspara) --> pfspara = 0x00000005
{
    return false;
}

Why does pfspara change to some bogus pointer? I can't reproduce the problem in debug, only in production.

Thanks.

Answer 1

If you are trying to debug optimized code in for example Visual Studio, you cannot always rely on the debugger properly showing the values of variables - especially not if the variable is unused so that the compiler probably optimizes it away.

Try running this instead:

bool Func(PFSPARA pfspara)
{
    printf("%x\n", pfspara);
    return false;
}

Answer 2

In general, this should never happen. Problems that can cause this type of symptoms include incompatibility in the compilation options between the calling and the caller modules, bad casting of member function pointers, or simply compiler bugs. You need to provide a lot more details about your problem: Show the real code, specify your compiler, specify what are the debug vs. production compilation flags, etc.