Re: [libvirt] [PATCH]: Fix VIR_ALLOC_N for 0 byte arrays

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).