I've seen the custom allocators mentioned many times as central to the value proposition. Do the allocators shipped with the standard library compose the system allocator, or are they completely distinct from the *alloc family shipped as part of libc?
You can ofc use the *alloc from libc if you want. Otherwise there are different ones in the standard library, ArenaAllocator wraps another allocator, FixedBufferAllocator uses a given byte slice. I recommend to take a look at https://ziglang.org/documentation/master/std/#std.heap to get an overview.