From 1de0e8ae5c4a793edc4f033deefb185d933238e4 Mon Sep 17 00:00:00 2001 From: Ben Pfaff Date: Fri, 8 Apr 2011 16:44:31 -0700 Subject: [PATCH] netdev-linux: Avoid "cleverness" in swap_uint64(). Obviously correct code is easier on everyone. As the C FAQ says: 20.15c: How can I swap two values without using a temporary? A: The standard hoary old assembly language programmer's trick is: a ^= b; b ^= a; a ^= b; But this sort of code has little place in modern, HLL programming. Temporary variables are essentially free, and the idiomatic code using three assignments, namely int t = a; a = b; b = t; is not only clearer to the human reader, it is more likely to be recognized by the compiler and turned into the most-efficient code (e.g. using a swap instruction, if available). The latter code is obviously also amenable to use with pointers and floating-point values, unlike the XOR trick. See also questions 3.3b and 10.3. --- lib/netdev-linux.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/lib/netdev-linux.c b/lib/netdev-linux.c index eecaaa59..1aa90934 100644 --- a/lib/netdev-linux.c +++ b/lib/netdev-linux.c @@ -1144,9 +1144,9 @@ netdev_linux_update_is_pseudo(struct netdev_dev_linux *netdev_dev) static void swap_uint64(uint64_t *a, uint64_t *b) { - *a ^= *b; - *b ^= *a; - *a ^= *b; + uint64_t tmp = *a; + *a = *b; + *b = tmp; } /* Retrieves current device stats for 'netdev'. */ -- 2.30.2