On Wed, May 10, 2017 at 12:18 AM, Segher Boessenkool
[off-list ref] wrote:

On Tue, May 09, 2017 at 03:59:27PM +0100, Andre Przywara wrote:

quoted

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I was able to build (bare-metal) toolchains for
all architectures except arc, m68k, tilegx and tilepro.

arc needs a more recent GCC; the other probably as well.  GCC 7 should
be out very soon, you probably want to wait for that :-)

Well, GCC 7 indeed builds better, but then again is a very new compiler.
For instance in the moment it spits a lot of warnings when compiling the
kernel (mostly due to some *printf analysis). It's not hard to fix, but
this will take a while to trickle in and it's questionable whether this
will be backported everywhere.
So in addition to GCC 7.1 I'd like to have at least GCC 6.3 around,
which builds kernels without warnings today.

If you don't want warnings, turn off the warnings or just don't look at
them...  or fix the problems?  Many of the new warnings point out actual
problems.

Many of those sprintf problems in the kernel have already been fixed.

I've been using gcc-7.0 for a long time and fixed a lot of bugs it found,
along with more harmless warnings, but I had disabled a couple of
warning options when I first installed gcc-7 and ended up ignoring
those.

The exact set of additional options I used is:

-Wimplicit-fallthrough=0 -Wno-duplicate-decl-specifier
-Wno-int-in-bool-context -Wno-bool-operation -Wno-format-truncation
-Wno-format-overflow

there were a couple of others that I sent kernel fixes for instead.
I should probably revisit that list and for each of them either
only enable it with "make W=1" or fix all known warnings.
In the long run, I'd actually hope to fix all W=1 warnings too
and enable them by default.

      Arnd