gmtime_r 和 gmtime_s 的区别 [英] difference between gmtime_r and gmtime_s

问题描述

这两个函数有什么区别?我使用的是 MinGW 4.8.0.

Which is the difference between these two functions? I'm using MinGW 4.8.0.

我知道 gmtime_r 是线程安全的(但如果从同一线程多次调用则不安全)但我不明白 gmtime_s

I know that gmtime_r is thread safe ( but not secure if called multiple time from the same thread) but I don't understand gmtime_s

推荐答案

区别在于 gmtime_r(3) 是一个标准SUSv2函数.在 Windows 环境中，最接近 gmtime_r() 的是 gmtime_s()，它的参数颠倒了:

The difference is that gmtime_r(3) is a standard SUSv2 function. The closest you can find to gmtime_r() on a windows environment is gmtime_s(), which has its arguments reversed:

• gmtime_r(const time_t*, struct tm*)
• gmtime_s(struct tm*, const time_t*)

基本上，它们都将时间值转换为 tm 结构.gmtime_r 然后返回指向该结构的指针(如果失败则返回 NULL)，而 gmtime_s 如果成功则返回 0，和 errno_t 以防失败.

Basically, they both convert a time value to a tm structure. gmtime_r then return a pointer to this structure (or NULL if failed), whereas gmtime_s returns 0 if successful, and a errno_t in case of failure.

tm 结构具有以下主体，从上面列出的两个文档中可以看出:

The tm structure has the following body, as can be seen from both docs listed above:

struct tm {
    int tm_sec;         /* seconds */
    int tm_min;         /* minutes */
    int tm_hour;        /* hours */
    int tm_mday;        /* day of the month */
    int tm_mon;         /* month */
    int tm_year;        /* year */
    int tm_wday;        /* day of the week */
    int tm_yday;        /* day in the year */
    int tm_isdst;       /* daylight saving time */
};

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