There's a discussion in "The Practice of Programming" of which is a better style when programming in straight C. The argument for casting was that could make porting to C++ easier. The argument against it went like that (hope I'm not botching it): if the appropriate header file was not included and consequently malloc() was implicitly assumed to return an int, then without a cast assigning the return value of malloc to say char* would likely trigger a warning, but the cast will silence the warning. This could be a real bug if the convention for returning an int was different from returning a pointer (say if one was returned via a register and the other wasn't.)

Or if you were programming on an 8086 in large memory model where int is 16 bit and a pointer is 32 bit (16 bit segment, 16 bit offset)

This makes me wonder if anyone ever did a compiler where malloc returned a segment + offset (I think that gives a 48 bit pointer) for a 386 class machine.