c - 为什么 difftime() 会返回一个 double 值？

Question

来自 difftime()'s man page :

double difftime(time_t time1, time_t time0);

The difftime() function returns the number of seconds elapsed between time time1 and time time0, represented as a double.

既然“秒数”不需要 float ，为什么这个函数返回一个double？

Answer 1

这documentation在这一点上更清楚:

On POSIX systems, time_t is measured in seconds, and difftime is equivalent to arithmetic subtraction, but C and C++ allow fractional units for time_t.

虽然POSIX requires time_t to be an integer type ，对于非 POSIX 系统，这可能会返回小数秒。