Mercurial > hg > octave-lyh > gnulib-hg
changeset 9317:f7ffc7248a3f
Fix some portability problems in the previous change.
author | Paul Eggert <eggert@cs.ucla.edu> |
---|---|
date | Mon, 08 Oct 2007 17:11:13 -0700 |
parents | ac5b4a469386 |
children | 18c67ec54b59 |
files | lib/xnanosleep.c |
diffstat | 1 files changed, 35 insertions(+), 22 deletions(-) [+] |
line wrap: on
line diff
--- a/lib/xnanosleep.c +++ b/lib/xnanosleep.c @@ -49,35 +49,48 @@ { enum { BILLION = 1000000000 }; - bool overflow = false; - double ns; + /* For overflow checking, use naive comparison if possible, widening + to long double if double is not wide enough. Otherwise, use <=, + not <, to avoid problems when TIME_T_MAX is less than SECONDS but + compares equal to SECONDS after loss of precision when coercing + from time_t to long double. This mishandles near-maximal values + in some rare (perhaps theoretical) cases but that is better than + undefined behavior. */ + bool overflow = ((time_t) ((double) TIME_T_MAX / 2) == TIME_T_MAX / 2 + ? TIME_T_MAX < seconds + : (time_t) ((long double) TIME_T_MAX / 2) == TIME_T_MAX / 2 + ? TIME_T_MAX < (long double) seconds + : TIME_T_MAX <= (long double) seconds); + struct timespec ts_sleep; assert (0 <= seconds); - /* Separate whole seconds from nanoseconds. - Be careful to detect any overflow. */ - ts_sleep.tv_sec = seconds; - ns = BILLION * (seconds - ts_sleep.tv_sec); - overflow |= ! (ts_sleep.tv_sec <= seconds && 0 <= ns && ns <= BILLION); - ts_sleep.tv_nsec = ns; + /* Separate whole seconds from nanoseconds. */ + if (! overflow) + { + time_t floor_seconds = seconds; + double ns = BILLION * (seconds - floor_seconds); + ts_sleep.tv_sec = floor_seconds; - /* Round up to the next whole number, if necessary, so that we - always sleep for at least the requested amount of time. Assuming - the default rounding mode, we don't have to worry about the - rounding error when computing 'ns' above, since the error won't - cause 'ns' to drop below an integer boundary. */ - ts_sleep.tv_nsec += (ts_sleep.tv_nsec < ns); + /* Round up to the next whole number, if necessary, so that we + always sleep for at least the requested amount of time. Assuming + the default rounding mode, we don't have to worry about the + rounding error when computing 'ns' above, since the error won't + cause 'ns' to drop below an integer boundary. */ + ts_sleep.tv_nsec = ns; + ts_sleep.tv_nsec += (ts_sleep.tv_nsec < ns); - /* Normalize the interval length. nanosleep requires this. */ - if (BILLION <= ts_sleep.tv_nsec) - { - if (ts_sleep.tv_sec == TIME_T_MAX) - overflow = true; - else + /* Normalize the interval length. nanosleep requires this. */ + if (BILLION <= ts_sleep.tv_nsec) { - ts_sleep.tv_sec++; - ts_sleep.tv_nsec -= BILLION; + if (ts_sleep.tv_sec == TIME_T_MAX) + overflow = true; + else + { + ts_sleep.tv_sec++; + ts_sleep.tv_nsec -= BILLION; + } } }