From 05453b37fc0343e53bc7f332047e901b3e1abb84 Mon Sep 17 00:00:00 2001 From: Rich Felker Date: Thu, 23 May 2013 14:31:02 -0400 Subject: [PATCH] fix overflow behavior of clock() function per Austin Group interpretation for issue #686, which cites the requirements of ISO C, clock() cannot wrap. if the result is not representable, it must return (clock_t)-1. in addition, the old code was performing wrapping via signed overflow and thus invoking undefined behavior. since it seems impossible to accurately check for overflow with the old times()-based fallback code, I have simply dropped the fallback code for now, thus always returning -1 on ancient systems. if there's a demand for making it work and somebody comes up with a way, it could be reinstated, but the clock() function is essentially useless on 32-bit system anyway (it overflows in less than an hour). it should be noted that I used LONG_MAX rather than ULONG_MAX, despite 32-bit archs using an unsigned type for clock_t. this discrepency with the glibc/LSB type definitions will be fixed now; since wrapping of clock_t is no longer supported, there's no use in it being unsigned. --- src/time/clock.c | 17 ++++++++++------- 1 file changed, 10 insertions(+), 7 deletions(-) diff --git a/src/time/clock.c b/src/time/clock.c index 78403af3..c348e398 100644 --- a/src/time/clock.c +++ b/src/time/clock.c @@ -1,15 +1,18 @@ #include -#include -#include "syscall.h" +#include int __clock_gettime(clockid_t, struct timespec *); clock_t clock() { struct timespec ts; - struct tms tms; - if (!__clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &ts)) - return ts.tv_sec*1000000 + ts.tv_nsec/1000; - __syscall(SYS_times, &tms); - return (tms.tms_utime + tms.tms_stime)*10000; + + if (__clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &ts)) + return -1; + + if (ts.tv_sec > LONG_MAX/1000000 + || ts.tv_nsec/1000 > LONG_MAX-1000000*ts.tv_sec) + return -1; + + return ts.tv_sec*1000000 + ts.tv_nsec/1000; } -- 2.25.1