CareerCup

Is any portion of the code, set to behave differently in Debug build & different in Ship build?

This has got to do with compiler optimizations turned on in release builds, which could violate read/write order assumptions.

Memory overrun into unused debug information.

Something like this?

main()
{
    int *buf = 0;
    assert(buf = malloc(size));
    *buf = 10;
}

different run time environments probably...external dependencies not considered

One possibility due to concurrency, debug mode runs slower, thus causing different thread interleaving from release mode. Or in a single threaded program, a faster program can lead
to a path that is never taken in debug mode, and this path has a bug in it. Things like that.

In C/C++ a possibility might be having code such as:

#ifdef _DEBUG
    // code that only runs for debug
#else
    // code that only runs for release
#endif

which causes the compiler to debug and release builds differently.