Re: [Xen-devel] [PATCH v2] Fix building error

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 04.02.15 at 16:43, <Ian.Jackson@xxxxxxxxxxxxx> wrote:
> Jan Beulich writes ("Re: [Xen-devel] [PATCH v2] Fix building error"):
>> On 15.01.15 at 12:26, <Ian.Jackson@xxxxxxxxxxxxx> wrote:
>> > Assuming that the underlying bug is intractible I think the right
>> > answer is for an affected developer to do one of the following, as a
>> > workaround: either, manually override Fortify when requesting a debug
>> > build (by setting EXTRA_CFLAGS_XEN_TOOLS), or manually override the
>> > -O0 setting.
> ...
>> Having run into this just now too, and seeing that the previous
>> discussion didn't really lead anywhere, I wonder what should be
>> done about this. I check as far back as I reasonably could, and
>> glibc apparently never supported _FORTIFY_SOURCE without
>> optimization. The change in behavior at some point simply was
>> that rather than disabling this silently, they now warn about it
>> (which of course is fatal for a build with -Werror). I also checked
>> Python, and they also seem to have been enabling
>> _FORTIFY_SOURCE forever. Consequently, with the previously
>> suggested patches not having found acceptance, how about
> ...
>> +PY_CFLAGS = $(patsubst -O0,-O1,$(CFLAGS)) $(APPEND_LDFLAGS)
> 
> This is still bad.  What if the user explicitly wants to build without
> optimisation ?  That's not unusual.  And it's only the combination of
> -O0 and FORTIFY that fails.  (And it's only on broken platforms that
> FORTIFY appears by default.)

Broken platforms? (Of course I ask without having any idea where
python-config takes that -D_FORTIFY_SOURCE=2 [together with
everything else it sets] from.)

Also I think overriding -O<n> here is no worse that Python adding
-DNDEBUG regardless of us doing a debug build. (Besides they
actually do pass -O2 too, just that our additions override this.)

> I guess I would tolerate a patch which spots the combination of
> _FORTIFY_SOURCE and -O0 and only in that case changes -O1 to -O0.

But that would have to happen in (I guess) setup.py, unless we want
to invoke "python-config --cflags" from the Makefile to find out. And
I don't see myself touching any Python code...

Jan


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel