针对不同系统的宏定义，对于Linux而言
/* port.h - portability defines */ #elif defined(linux) # define OS_Linux # define ARCH "Linux" #ifdef OS_Linux # define HAVE_DAEMON # define HAVE_SETSID # define HAVE_WAITPID # define HAVE_TM_GMTOFF # define HAVE_SENDFILE # define HAVE_LINUX_SENDFILE # define HAVE_SCANDIR # define HAVE_INT64T #endif /* OS_Linux */