[cmake-developers] RFC: CMake precompiled header support and custom compiler based implementation

[Adam Strzelecki]

> * The option to use existing headers instead of autogenerated ones.

My solution (which is about PCH support to existing CMake version) does not auto generate any headers.

> * Implementing PCH support without additional targets. ReactOS already has like 1000+ targets, and we currently use PCH on almost all of them, so imagine if this official implementation doubles our targets number.

My solution needs to generate additional target indeed for one pre-generated header, so if all your 1000+ targets will share same precompiled header (given the compiler flags don't change) then you will have just one (single) additional target.

If CMake will support PCH natively I don't see any reason it will need extra target, yet obviously there will be extra (Ninja) compiler rule for PCH.

-- Adam