C++ gettid() was not declared in this scope

Question

A simple program is: I would like to get the thread ID of both of the threads using this gettid function. I do not want to do the sysCall directly. I want to use this funct

Answer 1

The man page you refer to can be read online here. It clearly states:

Note: There is no glibc wrapper for this system call; see NOTES.

and

NOTES

Glibc does not provide a wrapper for this system call; call it using syscall(2).

The thread ID returned by this call is not the same thing as a POSIX thread ID (i.e., the opaque value returned by pthread_self(3)).

So you can't. The only way to use this function is through the syscall.

But you probably shouldn't anyway. You can use pthread_self() (and compare using pthread_equal(t1, t2)) instead. It's possible that boost::thread has its own equivalent too.

Answer 2

Additional to the solution provided by Glenn Maynard it might be appropriate to check the glibc version and only if it is lower than 2.30 define the suggested macro for gettid().

#if __GLIBC__ == 2 && __GLIBC_MINOR__ < 30
#include <sys/syscall.h>
#define gettid() syscall(SYS_gettid)
#endif

Answer 3

This is a silly glibc bug. Work around it like this:

#include <unistd.h>
#include <sys/syscall.h>
#define gettid() syscall(SYS_gettid)