Which gets at the real point: these compilers come with the system or are otherwise provided by the vendor for more general purposes. (If someone downloaded icc and used its cpp, monitoring license compliance is their problem). Someone with corporate lawyers to satisfy may well need to avoid GPL, so they would use neither gcc nor cpphs (but the alternatives after that are few on the ground, given that clang's cpp doesn't like being abused for Haskell source...).

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