Bug#841419: linux-source-4.7: debian linux source package incompatible with default gcc6 in unstable?

[Giacomo Mulas <gmulas@oa-cagliari.inaf.it>]

Package: linux-source-4.7
Version: 4.7.8-1
Severity: important

Dear Maintainer,

this morning the update of my debian sid system brought me a "medium"
upgrade for the linux source package. I therefore proceeded to (try to)
rebuild it, via a standard "make oldconfig" using the previous (it's a minor
revision, no big configuration change, so I did not expect problems with
it). Unfortunately, compilation immediately complained about hardening that
would not work because it's broken in the compiler, but still went on, just
to stop immediately thereafter with an unrecoverable error:
kernel/bounds.c:1:0: error: code model kernel does not support PIC mode

A bit of googling showed that this is apparently due to the recent upgrade
of the default gcc compiler in sid (6.2.0-7). Indeed, I verified that I
cannot even recompile the previous debian kernel source version, the one I 
am currently running, and that compiled flawlessly not more that a week ago.
I was able to get around the problem by forcing the use of gcc-5 instead of
gcc-6 via the MAKEFLAGS="CC=gcc-5" environment variable.

While I see that this problem cannot be really blamed on the debian linux
source package, it still makes it at least hard to use on a sid installation
with the default debian compiler, and should be fixed somewhere. Either by
requesting a different compiler than the one that does not work and
explaining how to use it instead of the default one, or by adding some
workaround compiler options if possible/necessary. Or by filing a
critical/important bug against the default compiler (I would say "fails to
build the kernel" is critical enough for the default compiler...).


Thanks in advance, bye
Giacomo Mulas


-- System Information:
Debian Release: stretch/sid
  APT prefers unstable
  APT policy: (401, 'unstable'), (10, 'experimental')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 4.7.5-jak (SMP w/4 CPU cores)
Locale: LANG=it_IT.utf8, LC_CTYPE=it_IT.utf8 (charmap=UTF-8) (ignored: LC_ALL set to it_IT.utf8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)

Versions of packages linux-source-4.7 depends on:
ii  binutils  2.27-9
ii  xz-utils  5.2.2-1.2

Versions of packages linux-source-4.7 recommends:
ii  bc                    1.06.95-9+b2
ii  gcc                   4:6.1.1-1
ii  libc6-dev [libc-dev]  2.24-5
ii  make                  4.1-9

Versions of packages linux-source-4.7 suggests:
ii  libncurses5-dev [ncurses-dev]  6.0+20160917-1
ii  libqt4-dev                     4:4.8.7+dfsg-9
ii  pkg-config                     0.29-4
ii  pkgconf [pkg-config]           0.9.12-1

-- no debconf information

-- debsums errors found:
debsums: missing file /usr/src/linux-source-4.7.tar.xz (from linux-source-4.7 package)