XL Fortran Enterprise Edition for AIX : User's Guide - IBM

Example
The control structure has the following layout and would be coded as such in C:
typedef struct {
pthread_key_t key;
int flags;
void *unused_1;
int unused_2;
} FORT_LOCAL_COMMON;
extern FORT_LOCAL_COMMON myblock;
The ″key″ field is a unique identifier that describes a threadlocal data area. Every
threadlocal common block has its own key. The ″flags″ field indicates whether a
key has been obtained for the common block. Within a C function, you should use
the ″key″ in the control block in a call to pthread_getspecific to obtain the
thread-specific address of the threadlocal common area.
! Example 1: "fort_sub" is invoked by multiple threads. This is an invalid example
! because "fort_sub" and "another_sub" both declare /block/ to be THREADLOCAL.
! They intend to share the common block, but they are executed by different threads.
SUBROUTINE fort_sub()
COMMON /block/ j
INTEGER :: j
!IBM* THREADLOCAL /block/
INTEGER a(10)
! Each thread executing fort_sub
! obtains its own copy of /block/.
...
!IBM* INDEPENDENT
DO index = 1,10
CALL another_sub(a(i))
END DO
...
END SUBROUTINE fort_sub
SUBROUTINE another_sub(aa) ! Multiple threads are used to execute another_sub.
INTEGER aa
COMMON /block/ j
! Each thread obtains a new copy of the
INTEGER :: j ! common block: /block/.
!IBM* THREADLOCAL /block/
...
aa = j
! The value of ’j’ is undefined.
END SUBROUTINE another_sub
For more information, see the THREADLOCAL directive, in the XL Fortran
Enterprise Edition for AIX Language Reference.
368 XL Fortran Enterprise Edition for AIX : User’s Guide