Replace useless tid parameters with NULL

[zorjen122]

No description provided.

[Barenboim]

At least, on macOS with clang, the function requires a non-null argument:

test.c:11:36: warning: null passed to a callee that requires a non-null argument [-Wnonnull]
        pthread_create(NULL, NULL, f, NULL);

[Barenboim]

zsh: segmentation fault  ./a.out

[Barenboim]

But this is legal :)

{
    pthread_create(&(pthread_t){0}, NULL, f, NULL);
}

[zorjen122]

至少，在带有 clang 的 macOS 上，该函数需要一个非 null 参数：

test.c:11:36: warning: null passed to a callee that requires a non-null argument [-Wnonnull]
        pthread_create(NULL, NULL, f, NULL);

After consulting posix data, yes, usually the compiler pthread_create implementation will dereference "tid" when attr==NULL. Thanks for your reply.
[posix-pthread_create]“....Upon successful completion, pthread_create() shall store the ID of the created thread in the location referenced by thread.”