On 07/05/13 12:38, Torbjorn Granlund wrote: Hi Torbjorn,
I am trying to use qemu to 1. cover more of the assembly code in GMP 2. check configuration logic of GMP but I am not as successful as I would like to be. The 2nd table of http://gmplib.org/devel/testsystems.html shows all emulated systems I am using, most of which are qemu-based.
Wow - that's a really impressive setup :)
Unfortunately, several of the qemu-based systems experience intermittent but common segfaults: 1. Linux mips64eb 2.6.32-5-5kc-malta #1 Sun Sep 23 12:29:36 UTC 2012 mips64 GNU/Linux 2. Linux mips64el 2.6.32-5-5kc-malta #1 Fri Feb 15 21:38:11 UTC 2013 mips64 GNU/Linux 3. Linux kick.gmplib.org 2.6.18-6-sparc32 #1 Sat Dec 27 09:13:12 UTC 2008 sparc GNU/Linux An example of a failure is: gmp/tests/cxx/t-ops2.cc: In function 'void checkz()': gmp/tests/cxx/t-ops2.cc:86: internal compiler error: Segmentation fault Please submit a full bug report, with preprocessed source if appropriate. See<URL:http://gcc.gnu.org/bugs.html> for instructions. For Debian GNU/Linux specific bug reporting instructions, see<URL:file:///usr/share/doc/gcc-4.1/README.Bugs>. The bug is not reproducible, so it is likely a hardware or OS problem. (This was from the sparc32 system.) rootrem.c: In function 'mpn_rootrem_internal': rootrem.c:120:1: internal compiler error: Segmentation fault Please submit a full bug report, with preprocessed source if appropriate. See<file:///usr/share/doc/gcc-4.6/README.Bugs> for instructions. The bug is not reproducible, so it is likely a hardware or OS problem. (From the mips64eb system.) I am aware of that these systems don't exactly use the kernel-of-the-week. Newer kernels I have tried cause non-boot. (I don't think I've tried any newer sparc kernel, as building that would require a stable sparc system...) I realise that linux might have been debugged until it works on real hardware, but that qemu might trigger untested linux execution paths. Yesterday, I disabled GMP testing on these qemu systems, as I got tired of the many false alarms, and since GMP looked bad. Is there any hope that these qemu systems will become stable? Or aren't these problems qemu's fault?
I actually spent quite a bit of time a couple of years ago trying to troubleshoot a similar intermittent buildfarm compiler blowout in a Xen x86 guest, and in the end it turned out to be simply a lack of memory (both physical and virtual) assigned to the VM.
It just so happened that the code in question was tickling a gcc bug which caused excess memory usage during compilation, but only when compiling with a certain combination of flags. This may not necessarily be the problem here, but it's certainly worth a little experimentation first before looking deeper into QEMU.
HTH, Mark.
