Re: [gentoo-user] Can't rebuild gentoo kernel-4.9.16 with gcc-5.4.0

[Rich Freeman]

On Tue, May 30, 2017 at 1:50 PM, Mick <michaelkintzios@×××××.com> wrote:
> On Tuesday 30 May 2017 13:08:39 Neil Bothwick wrote:
>> On Tue, 30 May 2017 04:20:17 -0700 (PDT), Mick wrote:
>> > > After gcc-config, make sure you run:
>> > > # env-update
>> > > # source /etc/profile
>> > >
>> > > It looks like something still points to your old compiler.
>> >
>> > Thanks Joost, I've rebooted many times since the move/rebuild of almost
>> > everything with gcc-5.4.0.  Actually, now that you mention it ... I
>> > can't recall if I rebuilt the linux-headers.  Hmm ... will look into
>> > that next.
>>
>> As you are rebuilding the kernel, it may be that you have parts still
>> built with the old compiler. Try running make clean.
>
> Yes!  That fixed my problem.  Thank you Neil and Joost.  :-)
>

This will go a lot slower if you're constantly rebuilding after
tweaking options, but I direct my kernel builds to a tmpfs.

mkdir /var/tmp/linux
make O=/var/tmp/linux oldconfig
make O=/var/tmp/linux -j#
make O=/var/tmp/linux modules_install
make O=/var/tmp/linux install
emerge @module-rebuild

This leaves your sources completely untouched - it will just be the
clean git repo (or wherever you get your sources from).  Note that if
you want to later build/upgrade any kernel modules you'll need to
create /var/tmp/linux and run:
make O=/var/tmp/linux modules_prepare

(This is because you don't just have all the needed files lying around
all the time for when portage needs them.)

Also, you need to make sure your config file is in /boot or that
/proc/config.gz support is enabled, because there won't be a
/usr/src/linux/.config file lying around for when portage does kernel
config checks.  It automatically falls back to the running kernel when
this is missing.

From what I understand this is actually what the linux devs consider
the preferred way to build kernels anyway.  Now, the downside is that
if not much has changed make can't re-use anything.  The upside is
that you always get a completely clean build, and since all the
objects end up in a tmpfs it builds a lot faster (compared to a clean
build on disk).  I switched over to this when my /usr/src moved to
tmpfs to cut down on wear, and also because upstream actually
recommends it.

But, aside from issues like the one you just ran into you won't really
run into much trouble building the way most people seem to do it.

-- 
Rich