qsort() ptrdiff_t may be larger than int

Morten Welinder <mwelinder@gmail.com> writes:

> The code looks wrong.  It assumes that pointers are no larger than ints.
> If pointers are larger than ints, the code does not necessarily compute
> a consistent ordering and qsort is allowed to do whatever it wants.
>
> Morten
>
> static int compare_object_pointers(const void *a, const void *b)
> {
> 	const struct object * const *pa = a;
> 	const struct object * const *pb = b;
> 	return *pa - *pb;
> }

Signed-off-by: Junio C Hamano <junkio@cox.net>

diff --git a/object.c b/object.c
index 427e14cae2deb42138a439f7b2d69d3e06bb9417..cf5931a9423cb2ecdd9f34e6c33ed0b714ce61bf 100644 (file)
--- a/object.c
+++ b/object.c
@@ -82,7 +82,12 @@ static int compare_object_pointers(const void *a, const void *b)
 {
        const struct object * const *pa = a;
        const struct object * const *pb = b;
-       return *pa - *pb;
+       if (*pa == *pb)
+               return 0;
+       else if (*pa < *pb)
+               return -1;
+       else
+               return 1;
 }
 
 void set_object_refs(struct object *obj, struct object_refs *refs)