ATTRIBUTES

Developer Guide and Reference

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ID 767251

Date 10/31/2024

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ATTRIBUTES

General Compiler Directive: Declares properties for specified variables.

!DIR$ ATTRIBUTES att[,att]...:: object[,object]...

att

Is one of the following options (or properties):

ALIAS	DLLEXPORT	REFERENCE
ALIGN	DLLIMPORT	STDCALL
ALLOCATABLE	EXTERN	VALUE
ALLOW_NULL	FORCEINLINE	VARYING
C	IGNORE_LOC	VECTOR
CODE_ALIGN	INLINE
CONCURRENCY_SAFE	MIXED_STR_LEN_ARG
CVF	NO_ARG_CHECK
DECORATE	NOCLONE
DEFAULT	NOINLINE

object

Is the name of a data object or procedure.

The following table shows which ATTRIBUTES options can be used with various objects:

Option	Variable and Array Declarations	Common Block Names ¹	Subprogram Specification and EXTERNAL Statements
ALIAS	No	Yes	Yes
ALIGN	Yes	No	No
ALLOCATABLE	Yes²	No	No
ALLOW_NULL	Yes	No	No
C	No	Yes	Yes
CODE_ALIGN	No	No	Yes^{5, 6}
CONCURRENCY_SAFE	No	No	Yes
CVF	No	Yes	Yes
DECORATE	No	No	Yes
DEFAULT	No	Yes	Yes
DLLEXPORT	Yes³	Yes	Yes
DLLIMPORT	Yes	Yes	Yes
EXTERN	Yes	No	No
FASTMEM	Yes	No	No
FORCEINLINE	No	No	Yes
IGNORE_LOC	Yes⁴	No	No
INLINE	No	No	Yes
MIXED_STR_LEN_ARG	No	No	Yes
NO_ARG_CHECK	Yes	No	Yes⁵
NOCLONE	No	No	Yes
NOINLINE	No	No	Yes
REFERENCE	Yes	No	Yes
STDCALL	No	Yes	Yes
VALUE	Yes	No	No
VARYING	No	No	Yes
VECTOR	No	No	Yes⁵
¹A common block name is specified as [/]common-block-name[/] ²This option can only be applied to arrays. ³Module-level variables and arrays only. ⁴This option can only be applied to INTERFACE blocks. ⁵This option cannot be applied to EXTERNAL statements. ⁶This option can be applied to named main programs.

These options can be used in function and subroutine definitions, in type declarations, and with the INTERFACE and ENTRY statements.

Options applied to entities available through use or host association are in effect during the association. For example, consider the following:


MODULE MOD1
  INTERFACE
    SUBROUTINE NEW_SUB
    !DIR$ ATTRIBUTES C, ALIAS:'othername' :: NEW_SUB
    END SUBROUTINE
  END INTERFACE
  CONTAINS
    SUBROUTINE SUB2
    CALL NEW_SUB
    END SUBROUTINE
END MODULE

In this case, the call to NEW_SUB within SUB2 uses the C and ALIAS options specified in the interface block.

Options C, STDCALL, REFERENCE, VALUE, and VARYING affect the calling conventions of routines:

You can specify C, STDCALL, REFERENCE, and VARYING for an entire routine.
You can specify VALUE and REFERENCE for individual arguments.

Examples


INTERFACE
   SUBROUTINE For_Sub (I)
     !DIR$ ATTRIBUTES C, ALIAS:'_For_Sub' :: For_Sub
     INTEGER I
   END SUBROUTINE For_Sub
END INTERFACE

You can assign more than one option to multiple variables with the same compiler directive. All assigned options apply to all specified variables. For example:


 !DIR$ ATTRIBUTES REFERENCE, VARYING, C :: A, B, C

In this case, the variables A, B, and C are assigned the REFERENCE, VARYING, and C options. The only restriction on the number of options and variables is that the entire compiler directive must fit on one line.

The identifier of the variable or procedure that is assigned one or more options must be a simple name. It cannot include initialization or array dimensions. For example, the following is not allowed:


 !DIR$ ATTRIBUTES C :: A(10)  ! This is illegal.

The following shows another example:


SUBROUTINE ARRAYTEST(arr)
!DIR$ ATTRIBUTES DLLEXPORT :: ARRAYTEST
   REAL(4) arr(3, 7)
   INTEGER i, j
   DO i = 1, 3
     DO j = 1, 7
       arr (i, j) = 11.0 * i + j
     END DO
   END DO
END SUBROUTINE

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