Not OP but the most common reason I've seen is that this was an additional restriction that they imposed for their project. The standard library includes a perfectly working malloc. You override it so that you can't end up calling it accidentally, either explicitly (i.e. your brain farts and you do end up malloc()-ing something) or implicitly (i.e by calling a function that ends up calling malloc down the line). The latter is what happens, and surprisingly easy and often. Not all libraries have the kind of documentation that glibc has, nor can you always see the code.