small fix for ccan/take/take.c

Hello.

I've decided to take a look at c-lighting code, because we might
consider using it in the future.

I found a small problem in ccan/take/take.c that only concerns code
that runs with CCAN_TAKE_DEBUG set (DEVELOPER=1 for c-lighting).

It is a small issue, but I decided to notify you as the author of the
code, anyway.

the issue is:
  in take_() function, potential failure of realloc for labelarr is not
  handled.

I attached a diff with a fix.

I thought that making a pull request for c-lighting would not be right,
as ccan is a separate project, but I did not find a way to report this
at http://git.ozlabs.org/, where ccan repo resides.

Therefore I wrote to you directly.

[ Minor whitespace changes --RR ]

ccan/take/take.c

@@ -32,9 +32,20 @@ void *take_(const void *p, const char *label)
 		}
 		takenarr = new;
 		/* Once labelarr is set, we maintain it. */
-		if (labelarr)
-			labelarr = realloc(labelarr,
-					   sizeof(*labelarr) * (max_taken+1));
+		if (labelarr) {
+                        const char **labelarr_new;
+			labelarr_new = realloc(labelarr,
+					       sizeof(*labelarr) * (max_taken+1));
+                        if (labelarr_new) {
+                                labelarr = labelarr_new;
+                        } else {
+                                /* num_taken will be out of sync with the size of
+                                 * labelarr after realloc failure.
+                                 * Just pretend that we never had labelarr allocated. */
+                                free(labelarr);
+                                labelarr = NULL;
+                        }
+                }
 		max_taken++;
 	}
 	if (unlikely(labelarr))