On Mon, May 05, 2014 at 08:32:34AM +0900, YAMAMOTO Takashi wrote: > > On Sat, May 03, 2014 at 09:01:01AM +0900, YAMAMOTO Takashi wrote: > >> xmalloc_cacheline API is relatively new. It's better > >> not to inherit the kludge from xmalloc. This kind of > >> kludge rather hurts these days. > >> > >> Signed-off-by: YAMAMOTO Takashi <yamam...@valinux.co.jp> > > > > I see basically three alternatives for xmalloc(0) and > > xmalloc_cacheline(0): > > > > 1. Assert-fail. > > > > 2. Return NULL. > > > > 3. Return a unique 1-byte block. > > > > I'm not a big fan of #1 because it can create corner cases where one > > must be extra careful, mainly when one is allocating a variable-length > > array that might occasionally have zero elements. > > > > #2 and #3 have about the same effect most of the time. Since > > dereferencing the pointer returned by #3 yields undefined behavior > > according to the C standard, there isn't much of an advantage to #3 over > > #2. The only practical difference is that occasionally a nonnull > > pointer indicates that some data structure has been initialized. > > > > I've always leaned toward #2, as a personal opinion, but I went with #3 > > in Open vSwitch xmalloc() because of my GNU background, since GNU code > > has a bias toward malloc(0) acting like malloc(1). (gnulib goes so far > > as to test for malloc(0) behavior and add a wrapper if it returns NULL.) > > > > So my preference is #2 or #3, leaning toward #3 since it's the behavior > > we've had in OVS for a long time. To me, #1 seems risky: it makes a > > rare corner case definitely deadly. > > thanks for explaining your reasoning. > i can understand it, although i still prefer failing loudly rather > than silently.
I guess I don't see an allocator that returns a 0-byte block in response to a 0-byte request as "failing". > i will drop this patch for now as it seems at least controversial. OK. _______________________________________________ dev mailing list dev@openvswitch.org http://openvswitch.org/mailman/listinfo/dev
