CVS commit: src/lib/libc/stdlib

[Kamil Rytarowski]

Module Name:    src
Committed By:   kamil
Date:           Thu Aug 20 22:27:49 UTC 2015

Modified Files:
        src/lib/libc/stdlib: reallocarr.c

Log Message:
Minor alterations to reallocarr(3)

Add comment about division.
Mark error branches with __predict_false().
Reduce one branch with the OR trick.


To generate a diff of this commit:
cvs rdiff -u -r1.4 -r1.5 src/lib/libc/stdlib/reallocarr.c

Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.


Modified files:

Index: src/lib/libc/stdlib/reallocarr.c
diff -u src/lib/libc/stdlib/reallocarr.c:1.4 src/lib/libc/stdlib/reallocarr.c:1.5
--- src/lib/libc/stdlib/reallocarr.c:1.4	Thu Aug 20 20:08:04 2015
+++ src/lib/libc/stdlib/reallocarr.c	Thu Aug 20 22:27:49 2015
@@ -1,4 +1,4 @@
-/* $NetBSD: reallocarr.c,v 1.4 2015/08/20 20:08:04 joerg Exp $ */
+/* $NetBSD: reallocarr.c,v 1.5 2015/08/20 22:27:49 kamil Exp $ */
 
 /*-
  * Copyright (c) 2015 Joerg Sonnenberger <jo...@netbsd.org>.
@@ -34,7 +34,7 @@
 #endif
 
 #include <sys/cdefs.h>
-__RCSID("$NetBSD: reallocarr.c,v 1.4 2015/08/20 20:08:04 joerg Exp $");
+__RCSID("$NetBSD: reallocarr.c,v 1.5 2015/08/20 22:27:49 kamil Exp $");
 
 #include "namespace.h"
 #include <errno.h>
@@ -70,14 +70,20 @@ reallocarr(void *ptr, size_t number, siz
 		return 0;
 	}
 
-	if ((number >= SQRT_SIZE_MAX || size >= SQRT_SIZE_MAX) &&
-	    number > SIZE_MAX / size) {
+	/*
+	 * Try to avoid division here.
+	 *
+	 * It isn't possible to overflow during multiplication if neither
+	 * operand uses any of the most significant half of the bits.
+	 */
+	if (__predict_false((number|size) >= SQRT_SIZE_MAX &&
+	                    number > SIZE_MAX / size)) {
 		errno = saved_errno;
 		return EOVERFLOW;
 	}
 
 	nptr = realloc(optr, number * size);
-	if (nptr == NULL) {
+	if (__predict_false(nptr == NULL)) {
 		result = errno;
 	} else {
 		result = 0;