Bug#798149: Compilation with the -O2 flag on i386 can lead to stuck exec
Package: gcc
Version: 1.145
When compiling flint version 2.5.2 (available from http://flintlib.org
or from the orig tarball of experimental's src:flint package), the
library testsuite fails on two tests (both in d_mat's directory: qr and
gso).
They fail by never returning -- the buildbots which checked my
experimental package terminated after 2h30min or 3h, but I have tried
waiting 12h).
The exact setting to trigger the failure is :
(1) i386 platform (debian arches i386, hurd-i386 or kfreebsd-i386). The
debian buildbots for other arches were ok (except alpha, unsupported by
upstream).
(2) -O2 switch : the debian package uses:
./configure --prefix=/usr --with-ntl CFLAGS='-D_FORTIFY_SOURCE=2 -g -O2
-fstack-protector-strong -Wformat -Werror=format-security'
(well, through dpkg-buildflags) but I was able to bissect those switches
and determined this is enough to trigger the problem :
./configure --prefix=/usr CFLAGS='-O2'
After that, "make" followed by "make check" will run tests, and d_mat's
qr should get stuck.
In the same situation, clang 3.5 and 3.8 fail by producing tests (not
the same ones) which trigger "Illegal instruction".
The previous gcc, 4.9.3-4, also gets stuck, in the same tests.
I hope that is detailed enough -- feel free to ask for more details,
Snark on #debian-science
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