Re: [PATCH bpf v2] tools: fix unavoidable GCC call in Clang builds

[Adrian Ratiu]

Hello Daniel,

On Tue, 08 Mar 2022, Daniel Borkmann <daniel@xxxxxxxxxxxxx> wrote:
> On 3/8/22 1:14 PM, Adrian Ratiu wrote: 
> > In ChromeOS and Gentoo we catch any unwanted mixed Clang/LLVM 
> > and GCC/binutils usage via toolchain wrappers which fail 
> > builds.  This has revealed that GCC is called unconditionally 
> > in Clang configured builds to populate GCC_TOOLCHAIN_DIR. 
> > Allow the user to override CLANG_CROSS_FLAGS to avoid the GCC 
> > call - in our case we set the var directly in the ebuild 
> > recipe.   In theory Clang could be able to autodetect these 
> > settings so this logic could be removed entirely, but in 
> > practice as the commit cebdb7374577 ("tools: Help 
> > cross-building with clang") mentions, this does not always 
> > work, so giving distributions more control to specify their 
> > flags & sysroot is beneficial.   Suggested-by: Manoj Gupta 
> > <manojgupta@xxxxxxxxxxxx> Suggested-by: Nathan Chancellor 
> > <nathan@xxxxxxxxxx> Acked-by: Nathan Chancellor 
> > <nathan@xxxxxxxxxx> Signed-off-by: Adrian Ratiu 
> > <adrian.ratiu@xxxxxxxxxxxxx> --- Changes in v2: 
> >    * Replaced variable override GCC_TOOLCHAIN_DIR -> 
> >    CLANG_CROSS_FLAGS 
>
> As I understand it from [0] and given we're late in the cycle, 
> this is targeted for bpf-next not bpf, right? 

Yes, let's target this for bpf-next. The issue was introduced in 
the 5.17 cycle but indeed it's late. I can do a stable backport to 
5.17 after it releases.

Thanks,
Adrian

> Thanks,
> Daniel
>
>    [0] https://lore.kernel.org/lkml/87czjk4osi.fsf@ryzen9.i-did-not-set--mail-host-address--so-tickle-me/