It depends on the implementation of malloc.

Generally malloc is an allocation mechanism on top of HeapAlloc that
provides optimisation by allocating a single large block and
sub-dividing it down more optimally than HeapAlloc. Additionally, a
debug malloc implementation may provide leak detection diagnostic
features.

Dave

In recent versions of VC, in the release version CRT, malloc delegates
almost directly to HeapAlloc, so the performance difference is negligable.

Tom