FreeBSD's __isthreaded equivalent in Linux

Question

FreeBSD's stdio.h has an extern declaration of variable '__isthreaded'. This variable is zero until a process has created a thread. It is used to avoid calling locking functions in libc when they are not required.

But this is not a portable way of checking presence of thread. Linux does not support this. Do we have any equivalent Variable or API in Linux? I am trying to port some code from FreeBSD to Linux.

Thanks in advance for your help.

Answer 1

What glibc does to provide almost the same feature is to define stub functions for most of the pthread library in glibc. These calls do nothing and are very fast.

Once libpthread.so is linked in, its symbols override the weak glibc symbols and then the real functions are called.

So include pthread and call the locking functions, but don't link with it.