[bug#64929] [PATCH] gnu: gcc-toolchain: Create a 'bin/cc' symlink.

[Maxime Devos]

Op 21-08-2023 om 16:30 schreef Attila Lendvai:
> ok, i see why this won't work.
>
> CC=(cc-for-target) is fine for packages, but the use-case that i'd like to 
> facilitate is `guix shell gcc-toolchain some-other-deps` and then build a 
> project manually from the opened shell.
>
> any ideas how to help/handle that use-case without disrupting cross-compilation 
> for packages?

IIUC, gcc-toolchain isn't used for "guix build" (I'm not really sure 
though), so if that's your use case, your current patch would work 
without problems w.r.t. cross-compilation.  Rhetorical question: why 
didn't I think of this when writing my previous message?

However, (assuming my assumption about gcc-toolchain is correct), 
applying the patch would create a discrepancy between the build 
environment from "guix build/guix shell -D ..." and "guix shell 
gcc-toolchain more-deps", which isn't nice and is potentially confusing.

I was going to suggest that the solution would be to modify your script 
to look for TARGET-cc when cross-compiling, but while that would be an 
improvement it wouldn't solve anything as Guix doesn't have TARGET-cc.

For an alternate proposal (which I think has been proposed before, but I 
don't recall where), it might be possible to create 'symlink' packages 
"symlink-cc-gcc" and "symlink-cc-clang", that respectively have the 
cc->gcc and cc->clang symlink (also cc->clang should be removed from the 
clang package, otherwise there is a collision and a preference for clang).

(I'm thinking of Debian's alternative system, but simplified (no 
priorities!) and based on packages.)

For --with-c-toolchain (*) (**) and the cross-compilation issue I 
mentioned, these should be forbidden for use in Guix packages (as in, 
"guix lint" doesn't like it/not accepted in Guix proper, if some other 
channel does it anyway, it's not recommended, but also not really any of 
Guix' concern).

(*) I don't know if clang and cross-compilation is supported yet by 
--with-c-toolchain.
(**) though with-c-toolchain isn't truly a concern, as it could simply 
adjust the symlink inputs ...

(I have the impression that I previously was against such symlink 
packages, but I don't recall actually writing a message about it.)

Best regards,
Maxime Devos.

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