Re: [gentoo-dev] [PATCH] toolchain-funcs.eclass: avoid using tc-getCPP in compiler checks

[Ionen Wolkens <ionen@gentoo.org>]

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On Wed, Feb 05, 2025 at 01:10:10PM -0500, Mike Gilbert wrote:
> We usually want to invoke cc -E rather than cpp directly. We should not
> rely on the quirk of tc-getCPP defaulting to "cc -E" when CPP is unset.

I think it's a good change, but just to note it could break things
that relied on CPP being what's used.

Aka these don't have a proper way to say "test this compiler" and,
given it uses CPP, it's what I ended up setting:

    CPP="${KERNEL_CC} -E" tc-is-clang ...

That's from nvidia-drivers ebuilds, which I'll fix real soon so no
need to worry about these. But I don't know what else may have done
this, not that I think it's going to be common.

I did something similar in linux-mod-r1.eclass but I took more
precaution there so it's not affected:

    # for toolchain-funcs, uses CPP > CC but set both not to make assumptions
    local CC=${KERNEL_CC} CPP="${KERNEL_CC} -E" LD=${KERNEL_LD}

I could cleanup the CPP bit if this is merged though. That it doesn't
use CC was confusing if anything thus needing a comment to explain
why it's being set.

Hopefully haven't forgot anything else I did, think wine & mingw things
are fine.
-- 
ionen

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