On Thu, 6 Dec 2007, Tom Hughes wrote: >>> Memcheck: mc_main.c:957 (get_sec_vbits8): Assertion 'n' failed. >>> Memcheck: get_sec_vbits8: no node for address 0x6FA9EA0 (0x6FA9EAC) >> >> It's a problem with the secondary V bits table in Memcheck. That table >> holds the full V bits for all memory bytes that are partially defined. >> It's happened a couple of times, but always in situations that are >> impossible for me to reproduce. If you are able to reduce it to a small >> test, or are able to do any debugging yourself, that would be very helpful. > > It is 100% repeatable for me but, interestingly, only on my machine at > home. My machine at work doesn't have the same problem. Both are > x86_64 machines with two cores and 4Gb of memory and both are running > Fedora 8! > [...] > Any suggestions for the best way to debug it?
The relevant code starts with this line, around line 838: /* --------------- Secondary V bit table ------------ */ It's a fairly basic data structure, the only notable thing is that we periodically garbage collect (GC) it, ie. remove stale nodes. The easy first thing to try is to turn off the GC, ie. make gcSecVBitTable() do nothing. If that makes the problem go away, then we know that the GC is removing nodes it shouldn't. It might also be useful if you can run with -v. The "memcheck GC" lines indicate when GCs are happening. Nick ------------------------------------------------------------------------- SF.Net email is sponsored by: Check out the new SourceForge.net Marketplace. It's the best place to buy or sell services for just about anything Open Source. http://sourceforge.net/services/buy/index.php _______________________________________________ Valgrind-developers mailing list Valgrind-developers@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/valgrind-developers
