https://svn.boost.org/trac10/ticket/10616 <p> I've noticed that boost::lockfree::queue does not work on the OSv operating system, crashing when used. </p> <p> After some investigation, I discovered the problem: lockfree::queue uses tagged_ptr, and that, when compiled on x86_64, uses tagged_ptr_ptrcompression which assumes that pointers always start with 16 zero bits. </p> <p> The thing is - the x86_64 standard does *not* guarantee that pointers must start with all zero bits. It just guarantees that pointers are so-called "canonical", meaning that the first 16 (usually) bits are either all 0, or all 1. But they *can* be all 1-s, and indeed in OSv, malloc()ed memory has addresses starting with all 1s. By the way, in Linux, kernel-space memory (as opposed to user-space memory) also has such addresses. </p> <p> But tagged_ptr::extract_ptr() assumes that the leading bits of pointers are always zero - which happens to be true on Linux's user-space memory but is not generally guaranteed by x86_64 (and isn't true on OSv). </p> <p> I'm not sure what to suggest as a fix. One not-really-safe-but-will-probably-work-in-practice option is to choose to fill the pointer with 0 or 1 bits depending on the 47th bit. Another not-quite-foolproof option is to assume that in one program all pointers will start with the same prefix (all 0 or all 1), so calculate this prefix once at runtime and then use it every time. </p> en-us /htdocs/site/boost.png https://svn.boost.org/trac10/ticket/10616 Trac 1.4.3 nyh@… Mon, 06 Oct 2014 05:54:09 GMT https://svn.boost.org/trac10/ticket/10616#comment:2 https://svn.boost.org/trac10/ticket/10616#comment:2 <ul> <li><strong>owner</strong> set to <span class="trac-author">timblechmann</span> </li> <li><strong>component</strong> <span class="trac-field-old">None</span> → <span class="trac-field-new">lockfree</span> </li> </ul> Ticket timblechmann Mon, 20 Oct 2014 04:33:45 GMT