bug#30756: GCC >= 6 '-isystem' and C_INCLUDE_PATH behavior changed, breaking

[Ludovic Courtès]

Hello!

Marius Bakke <address@hidden> skribis:

> The patch looks great to me.  Love how simple your solution was.  The
> #include_next issue be confusing and frustrating even for seasoned Guix
> developers, so I'm all for getting it in ASAP.

Great.  We’ll make new friends with this patch, I can tell you.  ;-)

> Can you check whether (gnu packages cross-base) can be adjusted in the
> same vein?  I.e. go back to CROSS_C_INCLUDE_PATH & co, and dropping the
> 'treat-glibc-as-system-header' phase from "cross-gcc-arguments".

Yes, though probably as a separate patch, if you don’t mind, because
cross-base is kinda orthogonal.

I’ve started looking at places where we manually fiddle with
CPATH/C_INCLUDE_PATH and found some more in build systems.  But then,
there are also quite a few individual packages that fiddle with it, so
it’ll certainly take some time before we find and address each of these.

Related to that, I’ll be posting a patch that clarifies search path
handling in commencement.scm—not a prerequisite, but a nice bonus IMO.

Thanks,
Ludo’.