[cfe-dev] Why clang needs to fork into itself?

[Yuri]

I noticed that even the simple command 'clang -c -emit-llvm c.cpp' calls 
fork, and forks into itself.
Why does it need to do this? This would potentially complicate 
profiling, debugging, etc. All tools should be fork-aware.
Also unnecessary operation must cause some performance hit.

It is understandable when compiler would, for example, fork into an 
external macro preprocessor, or assembler, or linker, but why into itself?

Yuri