> Isn't the right way of doing this to use a different implementation of malloc, rather than wrapping malloc with your own meta-malloc?

Yup [0].

There's even other complete libraries like tcmalloc [1] and jemalloc [2].

[0] https://stackoverflow.com/a/262481/1111557

[1] https://github.com/google/tcmalloc

[2] https://github.com/jemalloc/jemalloc

One reason I can think of wrapping malloc is that C is more likely to give you that than whatever OS-specific API you are going to use to get memory from the kernel (if you even have one!).