gettid() returns the thread ID of the current process. This is equal to the process ID (as returned by%uA0getpid(2)), unless the process is part of a thread group (created by specifying the CLONE_THREAD flag to the%uA0clone(2) system call). All processes in the same thread group have the same PID, but each one has a unique TID.
返回值
如果成功，返回当前进程的线程ID。
错误
这个调用永远是成功的。
遵循于
gettid()%uA0是Linux特有的，并应在该旨在是可移植的程序不被使用。
注意
Glibc does not provide a wrapper for this system call call it using%uA0syscall(2).