Re: [gentoo-dev] Should this be considered a gcc bug?
On Tue, Apr 21, 2015 at 09:57:16AM +0600, gro...@gentoo.org wrote:
Hello *,
There was a bug #526194 - dev-lisp/sbcl does not respect CFLAGS. It was
fixed by Mark Wright gie...@gentoo.org on Jan 31 - Feb 1. However,
after this fix the upstream CFLAGS were appended to the user-supplyed
${CFLAGS}. And the upstream CFLAGS contain -O3. So, is a user has, e.g.,
-O2 in his/her ${CFLAGS}, it was silently replaced by -O3. For some time,
nobody noticed this: gcc-4.8 happily compiled the C stuff in sbcl with
-O3.
The best fix here would be to ask upstream to stop putting -O3 in their
default CFLAGS.
Thanks,
William
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[gentoo-dev] Should this be considered a gcc bug?
Hello *,
There was a bug #526194 - dev-lisp/sbcl does not respect CFLAGS. It was
fixed by Mark Wright gie...@gentoo.org on Jan 31 - Feb 1. However,
after this fix the upstream CFLAGS were appended to the user-supplyed
${CFLAGS}. And the upstream CFLAGS contain -O3. So, is a user has, e.g.,
-O2 in his/her ${CFLAGS}, it was silently replaced by -O3. For some time,
nobody noticed this: gcc-4.8 happily compiled the C stuff in sbcl with
-O3.
However, after the upgrade to gcc-4.9 problems began (bug #544070). On
amd64, gcc is still happy co compile sbcl with -O3. However, on x86 this
leads to a crash of a freshly compiled sbcl runtime. Namely, the
combinations
-O2 -march=something
-O3
behave correctly, and produce a working sbcl; but
-O3 -march=something
lead to the crush. I have changed the above fix in sbcl-1.2.10 in such a
way that now it appends only -g -Wall -Wsign-compare to ${CFLAGS}, but
not -O3. This resolves the bug #544070, unless a user has -O3
-march=something in his/her ${CFLAGS}.
Shouldn't gcc-4.9 on x86 produce with -O3 something functionally
equivalent to the -O2 case, only more optimized? Should this be considered
a gcc-4.9 bug?
Andrey
Re: [gentoo-dev] Should this be considered a gcc bug?
Hi,
On Tue, 21 Apr 2015 09:57:16 +0600 (NOVT) gro...@gentoo.org wrote:
Hello *,
There was a bug #526194 - dev-lisp/sbcl does not respect CFLAGS. It was
fixed by Mark Wright gie...@gentoo.org on Jan 31 - Feb 1. However,
after this fix the upstream CFLAGS were appended to the user-supplyed
${CFLAGS}. And the upstream CFLAGS contain -O3. So, is a user has, e.g.,
-O2 in his/her ${CFLAGS}, it was silently replaced by -O3. For some time,
nobody noticed this: gcc-4.8 happily compiled the C stuff in sbcl with
-O3.
However, after the upgrade to gcc-4.9 problems began (bug #544070). On
amd64, gcc is still happy co compile sbcl with -O3. However, on x86 this
leads to a crash of a freshly compiled sbcl runtime. Namely, the
combinations
-O2 -march=something
-O3
behave correctly, and produce a working sbcl; but
-O3 -march=something
lead to the crush. I have changed the above fix in sbcl-1.2.10 in such a
way that now it appends only -g -Wall -Wsign-compare to ${CFLAGS}, but
not -O3. This resolves the bug #544070, unless a user has -O3
-march=something in his/her ${CFLAGS}.
Shouldn't gcc-4.9 on x86 produce with -O3 something functionally
equivalent to the -O2 case, only more optimized? Should this be considered
a gcc-4.9 bug?
Please look at gcc-4.9 manual for the list of -O3 expansion and
find what flag exactly causes this issue. There may be two reasons:
gcc bug and sbcl bug. While you have correctly pointed out that
this may be a problem in gcc, another possibility is that extra
optimization triggers some problem in the code itself, which causes
a segfault.
Best regards,
Andrew Savchenko
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Re: [gentoo-dev] Should this be considered a gcc bug?
On Tue, 21 Apr 2015 09:57:16 +0600 (NOVT)
gro...@gentoo.org wrote:
However, after this fix the upstream CFLAGS were appended to the
user-supplyed ${CFLAGS}. And the upstream CFLAGS contain -O3.
There is your problem. We filter out those compiler flags that affect
the output, so -O3 should go (and e.g. -Wall could stay).
jer
