Mattias Engdegård (CC'd) reports on IRC that apr_atomic_xchgptr() in
recent APR's is broken, and the brokenness can affect Subversion under
certain circumstances:
<@danielsh> wayita: t
< wayita> gcc 4.0.x or older
< wayita> apr 1.3.x or newer
< wayita> x86-64 only
< wayita> WORKAROUND: --disable-nonportable-atomics to APR's configure
< wayita> OS: any unix
< wayita> nature of the bug: apr_atomic_xchgptr() does not
initialize the return value
< wayita> https://issues.apache.org/bugzilla/show_bug.cgi?id=51851
< wayita> manifests as a segfault in svn.
It should be noted that this also explains the crash discussed in the
thread at http://svn.haxx.se/dev/archive-2011-08/0157.shtml, where it
was incorrectly guessed to be a compiler bug. (CC:ing the original
reporter)
