[libvirt] [PATCH libvirt-python 11/17] Import gnulib's xalloc_oversized macro

From: "Daniel P. Berrange" <berrange(a)redhat.com&gt; Signed-off-by: Daniel P. Berrange <berrange(a)redhat.com&gt; --- libvirt-override.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) diff --git a/libvirt-override.c b/libvirt-override.c index 246a15b..acd06a6 100644 --- a/libvirt-override.c +++ b/libvirt-override.c @@ -20,6 +20,7 @@ #include <Python.h> #include <libvirt/libvirt.h> #include <libvirt/virterror.h> +#include <stddef.h> #include "typewrappers.h" #include "build/libvirt.h" @@ -35,6 +36,21 @@ extern void initcygvirtmod(void); # define MIN(a,b) (((a) < (b)) ? (a) : (b)) #endif +/* Return 1 if an array of N objects, each of size S, cannot exist due + to size arithmetic overflow. S must be positive and N must be + nonnegative. This is a macro, not a function, so that it + works correctly even when SIZE_MAX < N. + + By gnulib convention, SIZE_MAX represents overflow in size + calculations, so the conservative dividend to use here is + SIZE_MAX - 1, since SIZE_MAX might represent an overflowed value. + However, malloc (SIZE_MAX) fails on all known hosts where + sizeof (ptrdiff_t) <= sizeof (size_t), so do not bother to test for + exactly-SIZE_MAX allocations on such hosts; this avoids a test and + branch when S is known to be 1. */ +#define xalloc_oversized(n, s) \ + ((size_t) (sizeof (ptrdiff_t) <= sizeof (size_t) ? -1 : -2) / (s) < (n)) + #if 0 # define DEBUG_ERROR 1 #endif -- 1.8.3.1