c++ - 错误 : 'CLOCK_MONOTONIC' undeclared (first use in this function)

Question

我尝试在 opencv 3.0 中构建基于像素强度比较的对象检测 (pico) 代码，在构建时我遇到了类似error: 'CLOCK_MONOTONIC' undeclared (first use in in这个功能)。谁能告诉我如何克服这些问题？？代码如下以及我得到的错误

float getticks()
{
    struct timespec ts;

    if(clock_gettime(CLOCK_MONOTONIC, &ts) < 0)
    {
        printf("clock_gettime error\n");

        return -1.0f;
    }

    return ts.tv_sec + 1e-9f*ts.tv_nsec;
}

我得到的错误是

picolrn.c:94:18: error: storage size of 'ts' isn't known
  struct timespec ts;
                  ^
picolrn.c:96:19: error: 'CLOCK_MONOTONIC' undeclared (first use in this function)
  if(clock_gettime(CLOCK_MONOTONIC, &ts) < 0)
                   ^
picolrn.c:96:19: note: each undeclared identifier is reported only once for each function it appears in
make.exe[2]: *** [build/Debug/MinGW_1-Windows/picolrn.o] Error 1

Answer 1

编译时添加命令行开关:-_POSIX_C_SOURCE=199309L。

没有它，time.h 头文件将不会定义它。