[OE-core] flto automake

Khem Raj raj.khem at gmail.com
Thu Dec 20 12:16:37 AEDT 2018

On Tue, Dec 18, 2018 at 4:42 PM Brad Bishop <bradleyb at fuzziesquirrel.com> wrote:
> > On Dec 18, 2018, at 1:08 PM, James Feist <james.feist at linux.intel.com> wrote:
> >
> > If you aren't planning on enabling flto in a repo you can ignore this email.
> >
> >
> > I've created a new class flto-automake https://github.com/openbmc/meta-phosphor/blob/master/classes/flto-automake.bbclass if you are enabling -flto in an autotools project you might be interested in. When using static libraries you may run into undefined references when building with Yocto. Yocto by default uses:

The changes are right but I think flto should also be a DISTRO_FEATURE
and this change should become effective only when flto is in

> >
> > export AR = "${HOST_PREFIX}ar"
> > export RANLIB = "${HOST_PREFIX}ranlib"
> >
> > for AR and RANLIB. This new class replaces these with the gcc equivalent wrappers that can work with the flto object files. This doesn't seem to be an issue for the CI build, it only shows up for Yocto builds. Reference: http://stackoverflow.com/questions/25878407/how-can-i-use-lto-with-static-libraries#comment67660913_25878408
> >
> > For Cmake I suggest looking at the way bmcweb handles it in CMakesLists:
> > https://github.com/openbmc/bmcweb/blob/master/CMakeLists.txt#L92

hardcoding is not right. We have cross versions of these tools
installed during OE build and we also have options to use non-gcc
compilers, e.g. llvm provides its own verisons of llvm-ar and
llvm-ranlib and llvm-nm which should be used when using clang
or other llvm based static compilers.
This is right fix for cross compiling with CMake

> >
> > Thanks,
> >
> > James
> Thanks James
> I wonder if this is something they would be interested in upstream.  I’ve copied
> the oe-core mailing list for possible comment.
> -brad
> --
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