On Fri, Oct 11, 2024 at 10:41:36PM -0400, Jason Merrill wrote: > The intent is that C++20 module header units obsolete PCH; they serve the > same function and are more flexible (you can import multiple header units).
Though, simple use of -std=c++20 or -std=c++23 doesn't imply one is using modules. Unfortunately there is no special driver option for PCH header writing, but until now one had to use explicit -fmodules to disable the PCH header writing and produce header unit. Can't we keep it that way, i.e. only disable PCH with explicit -fmodules, for implicit ones simply write both PCH and module header unit? Then users can decide when using it what they actually use, either they import a module header unit, or they include header and get PCH. Jakub