Re: [PATCH] test-skeleton.c (xrealloc): Support realloc-as-free

[Florian Weimer <fweimer at redhat dot com>]

On 06/23/2016 02:45 PM, Mike Frysinger wrote:
> On 23 Jun 2016 14:23, Florian Weimer wrote:
> > If the requested size is zero, realloc returns NULL, but the
> > deallocation is still successful.
>
> not exactly.  realloc(NULL, 0) will return a valid pointer (much
> like malloc(NULL) will).  code relies on this to generate cookies.

Ugh, right.  At least our malloc behaves in this way.  What about the 
attached patch?

Thanks,
Florian

test-skeleton.c (xrealloc): Support realloc-as-free

If the requested size is zero, realloc returns NULL, but the
deallocation is still successful, unless the pointer is also
NULL, when realloc behaves as malloc (0).

2016-06-23  Florian Weimer  <fweimer@redhat.com>

	* test-skeleton.c (xrealloc): Support deallocation with n == 0.

diff --git a/test-skeleton.c b/test-skeleton.c
index 0be4af1..d9bf989 100644
--- a/test-skeleton.c
+++ b/test-skeleton.c
@@ -109,10 +109,10 @@ __attribute__ ((unused))
 static void *
 xrealloc (void *p, size_t n)
 {
-  p = realloc (p, n);
-  if (p == NULL)
+  void *result = realloc (p, n);
+  if (result == NULL && (n > 0 || p == NULL))
     oom_error ("realloc", n);
-  return p;
+  return result;
 }
 
 /* Write a message to standard output.  Can be used in signal