How do you enable "#ifndef/#endif" blocks in makefile builds?
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I'm trying to enable debugging options in MuPDF. For some reason they have used `#ifndef NDEBUG` and `#endif` greying out code I want to use. I searched throughout the library but couldn't find any traces of NDEBUG defined anywhere... I've managed to workaround this by adding #undef NDEBUG in a header, but I would like to know if there is a more non-intrusive method to do so.

SO, can you enable "#ifndef/#endif" blocks from the makefile?

Also, why would you use `#ifndef` to grey out code? Isn't it supposed to be `#ifdef NDEBUG`?