[luke5441]

Yeah, but now compare this to pre-compiled headers. Maybe we should be happy with getting a standard way to have pre-compiled std headers, but now my build has a "scanning" phase which takes up some time.

[direwolf20]

Modules are a lot like precompiled headers, but done properly and not as a hack.

[nickelpro]

The OP does this and measures ~1.2x improvement over PCH.