From 74a5fef7cb0839c6b595f90c7914a62ac9d0bcf9 Mon Sep 17 00:00:00 2001 From: Rasmus Villemoes Date: Wed, 10 Dec 2014 15:51:27 -0800 Subject: lib/lcm.c: ensure correct result whenever it fits Ensure that lcm(a,b) returns the mathematically correct result, provided it fits in an unsigned long. The current version returns garbage if a*b overflows, even if the final result would fit. Signed-off-by: Rasmus Villemoes Cc: Martin K. Petersen Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- lib/lcm.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'lib/lcm.c') diff --git a/lib/lcm.c b/lib/lcm.c index b9c8de461e9e..01b3aa922dda 100644 --- a/lib/lcm.c +++ b/lib/lcm.c @@ -7,7 +7,7 @@ unsigned long lcm(unsigned long a, unsigned long b) { if (a && b) - return (a * b) / gcd(a, b); + return (a / gcd(a, b)) * b; else if (b) return b; -- cgit From 69c953c85c6cca85565ab32e4264b2efb6272e0e Mon Sep 17 00:00:00 2001 From: Rasmus Villemoes Date: Wed, 10 Dec 2014 15:51:29 -0800 Subject: lib/lcm.c: lcm(n,0)=lcm(0,n) is 0, not n Return the mathematically correct answer when an argument is 0. Signed-off-by: Rasmus Villemoes Cc: Martin K. Petersen Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- lib/lcm.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) (limited to 'lib/lcm.c') diff --git a/lib/lcm.c b/lib/lcm.c index 01b3aa922dda..51cc6b13cd52 100644 --- a/lib/lcm.c +++ b/lib/lcm.c @@ -8,9 +8,7 @@ unsigned long lcm(unsigned long a, unsigned long b) { if (a && b) return (a / gcd(a, b)) * b; - else if (b) - return b; - - return a; + else + return 0; } EXPORT_SYMBOL_GPL(lcm); -- cgit