On Mon, Mar 23, 2009 at 10:36:10AM +0000, Debian Bug Tracking System wrote: > Processing commands for cont...@bugs.debian.org: > > > clone 520713 -1 > Bug#520713: init script start hangs > Bug 520713 cloned as bug 520889. > > > reassign -1 libstdc++6 > Bug#520889: init script start hangs > Bug reassigned from package `schroot' to `libstdc++6'. > > > retitle -1 std::tr1::shared_ptr is broken on alpha unless code is compiled > > with -pthread > Bug#520889: init script start hangs > Changed Bug title to `std::tr1::shared_ptr is broken on alpha unless code is > compiled with -pthread' from `init script start hangs'.
Hi Debian GCC people, I cloned and reassigned this to you because while I worked around this bug in schroot, I do feel that this is fundamentally an issue in libstdc++. It appears from the bug investigation that the std::tr1::shared_ptr type is using a pthread mutex for locking (which is using futexes on the kernel side). I'm surprised about this because I thought it would just be using atomic increment/decrement (unless this is an alpha-specific implementation detail), but this is not in itself a problem. What did surprise me is that - my program is single threaded; it does not directly use any pthread- related stuff, just types from the ISO C++ Standard, and its TR1 addendum. - I did therefore not expect there would be a requirement to compile with -pthread in order to get a functional program. - On all architectures I'm aware of other than alpha, the code works correctly. - On alpha it crashes with a failed libc/libstdc++ assertion during object construction (where I am creating a new type instance which is returned contained within a shared_ptr). The stack trace showed it failing in my object constructor called from my clone() method which returns a shared_ptr (the actual ctor is private), but the pthread failure subsequently points the blame at shared_ptr, since I'm not using any pthread stuff myself. - One of the traces attached to the bug report shows a failure inside a Boost header; it's possible that it's an interaction between the boost and libstdc++ headers, but I can't be sure of that. I have Cc'd weasel, who originally found this bug on alpha. I don't have any alpha hardware myself, so you would probably need to ask weasel or one of the alpha porters if you need any alpha- specific expertise. Regards, Roger -- .''`. Roger Leigh : :' : Debian GNU/Linux http://people.debian.org/~rleigh/ `. `' Printing on GNU/Linux? http://gutenprint.sourceforge.net/ `- GPG Public Key: 0x25BFB848 Please GPG sign your mail. -- To UNSUBSCRIBE, email to debian-gcc-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org
