std::thread (c++11) 中使用的函数可以有 [[noreturn]] 吗？

Question

For std::thread t(foo); , does it ever make sense to have a foo [[noreturn]] () {...} ? For ex. for a detached thread (Used as a sort of daemon until the apps completion)?

Answer 1

Thread does not make a new process and does not use fork or exec, it makes a thread which should definitely eventually return. If your thread function never returns you'll hang on std::thread::join

Answer 2

Would it be of any benefit on gcc/clang to mark the function used for the thread with [[noreturn]]?

Thread functions normally do return. So no, they must not be marked with [[noreturn]] .

Unless they are coded to have an infinite loop, block forever, or call functions that terminate the thread or the process. In that case you might like to mark them as noreturn .

Note, that if you are using low-level functions like pthread_create to create a thread or other function which definition is not available at compile time, noreturn attribute will not have any effect on the code that invokes your function through a pointer.

The return value of a thread function of a detached thread is ignored.

Answer 3

I expect it (std::thread construction) to be some kind of fork + execve variation on my system and once successful it would have nothing to return to.

std::thread creates a separate thread (within the same process). fork + execve work on multiple processes.

Would it be of any benefit on gcc/clang to mark the function used for the thread with [[noreturn]]?

Only if the function you pass to std::thread does not return (that is, if the function calls std::exit, std::terminate, throws in all cases or starts an infinite loop, and so on).