Or globally replace the new and delete operators to call malloc & free, as they commonly already do such as in libstd++ and libc++ But having malloc/free cross

Or globally replace the new and delete operators to call malloc & free, as they commonly already do such as in libstd++ and libc++ But having malloc/free cross a library boundary (that is library A malloc and wants the caller in a different library to call free) is also a code smell in general and potentially very problematic. So you'll be generally doing custom deleters regardless