[OE-core] go-cross: incorrect dependency on tune-specific libgcc

[Patrick Ohly]

On Mon, 2017-04-10 at 14:49 +0200, Patrick Ohly wrote:
> Hello!
> 
> I'm currently extending the yocto-compat-layer.py so that it can detect
> invalid signature changes when changing MACHINE. go-cross-x86_64 shows
> up as broken when comparing signatures for MACHINE=intel-corei7-64 and
> MACHINE=qemux86-64.
> 
> Both machines share the same go-cross-x86_64, but that DEPENDS on
> libgcc:
> 
> meta/recipes-devtools/go/go.inc:# libgcc is required for the target specific libraries to build properly
> meta/recipes-devtools/go/go.inc:DEPENDS += "go-bootstrap-native libgcc"
> 
> And libgcc itself depends on the tune flags for the target architecture
> and thus is different for these two machines:
> 
> $ bitbake-diffsigs -t go-cross-x86_64 do_prepare_recipe_sysroot -s 563f419e3854c2351e2cbbf33a9025f6 64e378fd9853a6cd6a4e7f684f52d2fc
> Hash for dependent task gcc/libgcc_6.3.bb.do_populate_sysroot changed from afb6b55c0e2b7d2e816b3d2d214a7326 to 208fac5ae428b07a4aa491b130879e4a
>   Hash for dependent task gcc/libgcc_6.3.bb.do_multilib_install changed from 596e1612d7b84b7a9c1b409ee78cca89 to d41e2e835d0abe7646e53e3d63ce00cd
>     Hash for dependent task gcc/libgcc_6.3.bb.do_install changed from 9ca4126c69fcceb410253a0603c3d76b to cb0c49687a91ea17f1027c6394baacab
>       Hash for dependent task gcc/libgcc_6.3.bb.do_compile changed from ab80902424c73af49257cc3f6fe049aa to 436f978a703476968bd5ae1c1915ee5a
>         Hash for dependent task gcc/libgcc_6.3.bb.do_configure changed from eb0c36d87f32ce1ceb7d1e42609578fb to f62c98806faf3a28c2144919b89d3460
>           Hash for dependent task gcc/libgcc_6.3.bb.do_prepare_recipe_sysroot changed from b037b950e346bef71a4f8fd2c6a2195c to d4564b5730941279392932e3c670a5a5
>             Hash for dependent task gcc/libgcc_6.3.bb.do_fetch changed from e64cd9e029ed63ba3a09e5fe085b7057 to ea4d3f9d10544219ceb8591d5a5a4041
>               basehash changed from 8744593af2eddb60244788f2b9476e2d to dabeb22478ef501e35311af75119a2cf
>               Variable TUNE_CCARGS value changed:
>               " -m64 [--march=corei7 -mtune=corei7-] {+-march=core2 -mtune=core2 -msse3+} -mfpmath=sse [--msse4.2-]"
> 
> Does this fix look correct? It turns go-cross into a package that is
> specific to the tune flags for the target. 

[...]

> The alternative would be to drop the libgcc dependency, but I have no
> idea whether that would work at all.

Besides Bruce who pointed out the implications on recipes depending on
go-cross-${TARGET_ARCH}, Richard also had concerns about making go-cross
tune-specific, so I ended up testing the libgcc removal approach. It
happened to build okay, so the patch that I ended up proposing (see
"go-cross: avoid libgcc dependency") just removes libgcc from DEPENDS
for go-cross.

I need to revise the method how its done (i.e. not with DEPENDS_remove),
but besides that, can anyone explain whether such a change might hit
some problems somewhere? Khem?

-- 
Best Regards, Patrick Ohly

The content of this message is my personal opinion only and although
I am an employee of Intel, the statements I make here in no way
represent Intel's position on the issue, nor am I authorized to speak
on behalf of Intel on this matter.