Message ID | 20180620121427.25397-2-albert.aribaud@3adev.fr |
---|---|

State | New |

Headers | show |

diff --git a/include/time.h b/include/time.h index 5afb12305e..63cc855749 100644 --- a/include/time.h +++ b/include/time.h @@ -125,6 +125,12 @@ extern char * __strptime_internal (const char *rp, const char *fmt, struct tm *tm, void *statep, locale_t locparam) attribute_hidden; +#if __TIMESIZE == 64 +# define __difftime64 __difftime +#else +extern double __difftime64 (__time64_t time1, __time64_t time0); +#endif + extern double __difftime (time_t time1, time_t time0); /* Use in the clock_* functions. Size of the field representing the diff --git a/time/difftime.c b/time/difftime.c index 7c5dd9898b..fbc7ad9d57 100644 --- a/time/difftime.c +++ b/time/difftime.c @@ -30,87 +30,75 @@ /* Return the difference between TIME1 and TIME0, where TIME0 <= TIME1. time_t is known to be an integer type. */ -static double -subtract (time_t time1, time_t time0) +static double subtract (__time64_t time1, __time64_t time0) { - if (! TYPE_SIGNED (time_t)) - return time1 - time0; - else - { - /* Optimize the common special cases where time_t - can be converted to uintmax_t without losing information. */ - uintmax_t dt = (uintmax_t) time1 - (uintmax_t) time0; - double delta = dt; - - if (UINTMAX_MAX / 2 < INTMAX_MAX) - { - /* This is a rare host where uintmax_t has padding bits, and possibly - information was lost when converting time_t to uintmax_t. - Check for overflow by comparing dt/2 to (time1/2 - time0/2). - Overflow occurred if they differ by more than a small slop. - Thanks to Clive D.W. Feather for detailed technical advice about - hosts with padding bits. + /* Optimize the common special cases where __time64_t + can be converted to uintmax_t without losing information. */ + uintmax_t dt = (uintmax_t) time1 - (uintmax_t) time0; + double delta = dt; - In the following code the "h" prefix means half. By range - analysis, we have: + if (UINTMAX_MAX / 2 < INTMAX_MAX) +{ + /* This is a rare host where uintmax_t has padding bits, and possibly + information was lost when converting time_t to uintmax_t. + Check for overflow by comparing dt/2 to (time1/2 - time0/2). + Overflow occurred if they differ by more than a small slop. + Thanks to Clive D.W. Feather for detailed technical advice about + hosts with padding bits. - -0.5 <= ht1 - 0.5*time1 <= 0.5 - -0.5 <= ht0 - 0.5*time0 <= 0.5 - -1.0 <= dht - 0.5*(time1 - time0) <= 1.0 + In the following code the "h" prefix means half. By range + analysis, we have: - If overflow has not occurred, we also have: + -0.5 <= ht1 - 0.5*time1 <= 0.5 + -0.5 <= ht0 - 0.5*time0 <= 0.5 + -1.0 <= dht - 0.5*(time1 - time0) <= 1.0 - -0.5 <= hdt - 0.5*(time1 - time0) <= 0 - -1.0 <= dht - hdt <= 1.5 + If overflow has not occurred, we also have: - and since dht - hdt is an integer, we also have: + -0.5 <= hdt - 0.5*(time1 - time0) <= 0 + -1.0 <= dht - hdt <= 1.5 - -1 <= dht - hdt <= 1 + and since dht - hdt is an integer, we also have: - or equivalently: + -1 <= dht - hdt <= 1 - 0 <= dht - hdt + 1 <= 2 + or equivalently: - In the above analysis, all the operators have their exact - mathematical semantics, not C semantics. However, dht - hdt + - 1 is unsigned in C, so it need not be compared to zero. */ + 0 <= dht - hdt + 1 <= 2 - uintmax_t hdt = dt / 2; - time_t ht1 = time1 / 2; - time_t ht0 = time0 / 2; - time_t dht = ht1 - ht0; + In the above analysis, all the operators have their exact + mathematical semantics, not C semantics. However, dht - hdt + + 1 is unsigned in C, so it need not be compared to zero. */ - if (2 < dht - hdt + 1) - { - /* Repair delta overflow. + uintmax_t hdt = dt / 2; + __time64_t ht1 = time1 / 2; + __time64_t ht0 = time0 / 2; + __time64_t dht = ht1 - ht0; - The following expression contains a second rounding, - so the result may not be the closest to the true answer. - This problem occurs only with very large differences. - It's too painful to fix this portably. */ + if (2 < dht - hdt + 1) + { + /* Repair delta overflow. - delta = dt + 2.0L * (UINTMAX_MAX - UINTMAX_MAX / 2); - } + The following expression contains a second rounding, + so the result may not be the closest to the true answer. + This problem occurs only with very large differences. + It's too painful to fix this portably. */ + + delta = dt + 2.0L * (UINTMAX_MAX - UINTMAX_MAX / 2); } +} - return delta; - } + return delta; } /* Return the difference between TIME1 and TIME0. */ double -__difftime (time_t time1, time_t time0) +__difftime64 (__time64_t time1, __time64_t time0) { - /* Convert to double and then subtract if no double-rounding error could + /* Convert to long double and then subtract if no double-rounding error could result. */ - if (TYPE_BITS (time_t) <= DBL_MANT_DIG - || (TYPE_FLOATING (time_t) && sizeof (time_t) < sizeof (long double))) - return (double) time1 - (double) time0; - - /* Likewise for long double. */ - - if (TYPE_BITS (time_t) <= LDBL_MANT_DIG || TYPE_FLOATING (time_t)) + if (TYPE_BITS (__time64_t) <= LDBL_MANT_DIG) return (long double) time1 - (long double) time0; /* Subtract the smaller integer from the larger, convert the difference to @@ -118,4 +106,16 @@ __difftime (time_t time1, time_t time0) return time1 < time0 ? - subtract (time0, time1) : subtract (time1, time0); } + +#if __TIMESIZE != 64 + +/* Return the difference between TIME1 and TIME0. */ +double +__difftime (time_t time1, time_t time0) +{ + return __difftime64 (time1, time0); +} + +#endif + strong_alias (__difftime, difftime)