[PATCH] D69825: [Clang][Driver] Re-use the calling process instead of creating a new process for the cc1 invocation

[Reid Kleckner via Phabricator via cfe-commits]

rnk added a comment.

I'd be fine with the cmake var and the env var and no driver flag.

I think clang developers on Darwin probably want the single-process `clang -c` behavior (that's how I interpreted what Duncan said), even though Apple as a distributor of clang wants the multi-process behavior. I would skip the platform check and in upstream clang and suggest that Apple customize the CMake variable when producing the XCode tools package. But, that's just my opinion, please disagree if you don't like that idea.

Lastly, we could make the environment variable more cross-platform by calling it `CLANG_SPAWN_CC1` to be inclusive of OSs where fork doesn't exist. Besides, doesn't clang use `posix_spawn` on Mac anyway?


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  https://reviews.llvm.org/D69825/new/

https://reviews.llvm.org/D69825