This should not be inlined. This should probably use a

weak alias as well...

libc/sysdeps/linux/e1/vfork.c

@@ -3,5 +3,5 @@
 #include <sys/errno.h>
 
 #define __NR___libc_vfork __NR_vfork
-inline	_syscall0(pid_t, __libc_vfork);
-inline	_syscall0(pid_t, vfork);
+_syscall0(pid_t, __libc_vfork);
+_syscall0(pid_t, vfork);