C++ STL with jemalloc

Question

How is it possible to use C++ STL containers with jemalloc (or any other malloc implementation)?

Is it as simple as include jemalloc/jemalloc.h

Answer 1

Writing an allocator is going to be the easiest solution, since the stl was designed to have interchangeable allocators. This will be the easiest path.

Some projects play games try to get the alternate malloc implementation to replace the malloc and news provided by the compiler's companion library. That's prone to all sorts of issues because you end up relying on specific implementation details of your compiler and the library it normally uses. This path is fraught with danger.

Some dangers of trying to replace malloc globally:

• Static initializer order has limited guarantees in C++. There's no way to guarantee the allocator replacement is initialized before the first caller tries to use it, unless you ban static objects that might allocate memory. The runtime doesn't have this problem, since the compiler and the runtime work together to make sure the runtime is fully initialized before initializing any statics.
• If you dynamically link to the runtime library, then there's no way to ensure some of the runtime library's code isn't already bound to its own implementation. Trying to modify the compiler's runtime library might lead to licensing issues when redistributing your application.
• All other methods of allocation might not always ultimately rely on malloc. For example, an implementation of new might bypass malloc for large allocations and directly call the OS to allocate memory. That requires tracking to make sure such allocations aren't accidentally sent to the replacement free.

I believe Chromium and Firefox has both replaced the allocator, but they play some dirty tricks and probably have to update their approach as the compiler, linker, and runtime evolve.