For 0.4.3, danpb's new memory management scheme went into libvirt. This is fine, except that is subtly alters the semantics of malloc(), calloc(), and realloc(). In particular, if you say: foo = malloc(0); glibc will happily return a non-NULL pointer to you. However, with the new memory management stuff, if you say: foo = VIR_ALLOC(0); you will actually get a NULL pointer back. Personally, I think this is a dangerous deviation from malloc() semantics that everyone is used to, and is indeed causing problems with the remote driver. The short of it is that the remote driver allocates memory on behalf of the remote side using VIR_ALLOC_N, and this call is returning NULL so that the NULL checks elsewhere in the code fire and return failure. The attached patch fixes this situation by removing the 0 checks from the memory allocation paths, and just lets them fall through to the normal malloc(), calloc(), or realloc() routines, restoring old semantics.

On Thu, Jun 19, 2008 at 10:49:59AM +0200, Chris Lalancette wrote: > Hello, > For 0.4.3, danpb's new memory management scheme went into libvirt. This is > fine, except that is subtly alters the semantics of malloc(), calloc(), and > realloc(). In particular, if you say: > > foo = malloc(0); > > glibc will happily return a non-NULL pointer to you. However, with the new > memory management stuff, if you say: > > foo = VIR_ALLOC(0); > > you will actually get a NULL pointer back. Personally, I think this is a > dangerous deviation from malloc() semantics that everyone is used to, and is > indeed causing problems with the remote driver. The short of it is that the > remote driver allocates memory on behalf of the remote side using VIR_ALLOC_N, > and this call is returning NULL so that the NULL checks elsewhere in the code > fire and return failure. > > The attached patch fixes this situation by removing the 0 checks from the memory > allocation paths, and just lets them fall through to the normal malloc(), > calloc(), or realloc() routines, restoring old semantics. > > Signed-off-by: Chris Lalancette <clalance(a)redhat.com&gt; Agreed, it's a problem, +1, but since Dan explicitely made the == 0 test to return NULL he probably had a purpose about this (I suspect detecting 0 sized memory allocations).