Comment by lifthrasiir

Accepting a null pointer in free is a very easy part of the conformance and I am yet to see a libc implementation that doesn't so far, so your statement should be pretty much outdated even if it were true. And since malloc-free interface is so popular in C, other allocators are also commonly modelled after that (plus their own APIs) anyway; jemalloc for example has an usual free with the standard interface.