[pflats]

In C and C-derived languages, the C preprocessor can do some work on its own before anything ever hits the compiler. You can put a block of code like:

    #ifdef DEBUG
    if (pw == "backdoor")
      return true;
    #endif

And then when you want to have your backdoor active, just #define DEBUG somewhere upstream. That way, the backdoor code will never even be compiled in a non-debug program.