# Standard intrinsic module ISO_C_BINDING

## 1 Name

iso_c_binding — standard intrinsic module

## 2 Usage

USE,INTRINSIC :: ISO_C_BINDING

(The ',INTRINSIC ::' part is optional.)

## 3 Synopsis

ISO_C_BINDING provides named constants, types and procedures that are useful in a mixed-language (C and Fortran) program.

## 4 Parameter Descriptions

### 4.1 Kind Parameter Values

The following parameters are all KIND values for matching C types to a Fortran type and kind. If a particular C type has no matching Fortran kind, the parameter value will be negative.
  INTEGER,PARAMETER :: c_int = ...
INTEGER,PARAMETER :: c_short = ...
INTEGER,PARAMETER :: c_long = ...
INTEGER,PARAMETER :: c_long_long = ...
INTEGER,PARAMETER :: c_signed_char = ...
INTEGER,PARAMETER :: c_size_t = ...
INTEGER,PARAMETER :: c_intmax_t = ...
INTEGER,PARAMETER :: c_intptr_t = ...

Kind parameter values for the C integral types int, short, long, long long, signed char, c_size_t, intmax_t and c_intptr_t. These are all kind values for type INTEGER.

  INTEGER,PARAMETER :: c_int8_t = ...
INTEGER,PARAMETER :: c_int16_t = ...
INTEGER,PARAMETER :: c_int32_t = ...
INTEGER,PARAMETER :: c_int64_t = ...
INTEGER,PARAMETER :: c_int_least8_t = ...
INTEGER,PARAMETER :: c_int_least16_t = ...
INTEGER,PARAMETER :: c_int_least32_t = ...
INTEGER,PARAMETER :: c_int_least64_t = ...
INTEGER,PARAMETER :: c_int_fast8_t = ...
INTEGER,PARAMETER :: c_int_fast16_t = ...
INTEGER,PARAMETER :: c_int_fast32_t = ...
INTEGER,PARAMETER :: c_int_fast64_t = ...

Kind parameter values for the C integral types int8_t to int_fast64_t. These are all kind values for type INTEGER.

  INTEGER,PARAMETER :: c_float = ...
INTEGER,PARAMETER :: c_double = ...
INTEGER,PARAMETER :: c_long_double = ...

Kind parameter values for the C floating-point types float, double and long double. These are all kind values for type REAL.

  INTEGER,PARAMETER :: c_float_complex = c_float
INTEGER,PARAMETER :: c_double_complex = c_double
INTEGER,PARAMETER :: c_long_double_complex = c_long_double

Kind parameter values for the C _Complex family of types. These always have exactly the same values as c_float et al, and are included only for unnecessary redundancy.

  INTEGER,PARAMETER :: c_bool = ...

Kind parameter value for the C type _Bool, for use with the LOGICAL type.

  INTEGER,PARAMETER :: c_char = ..

Kind parameter value for the C type char, for use with the CHARACTER type.

### 4.2 Character Constants

The following parameters give Fortran values for all of the C “backslash” escape sequences.
  CHARACTER,PARAMETER :: c_null_char = char(0)         ! C '\0'
CHARACTER,PARAMETER :: c_alert = achar(7)            ! C '\a'
CHARACTER,PARAMETER :: c_backspace = achar(8)        ! C '\b'
CHARACTER,PARAMETER :: c_form_feed = achar(12)       ! C '\f'
CHARACTER,PARAMETER :: c_new_line = achar(10)        ! C '\n'
CHARACTER,PARAMETER :: c_carriage_return = achar(13) ! C '\r'
CHARACTER,PARAMETER :: c_horizontal_tab = achar(9)   ! C '\t'
CHARACTER,PARAMETER :: c_vertical_tab = achar(11)    ! C '\v'


### 4.3 Pointer Constants

  TYPE(c_ptr),PARAMETER :: c_null_ptr = c_ptr(...)

This is a C null pointer, equivalent to (void *)0 in C.

  TYPE(c_funptr),PARAMETER :: c_null_funptr = c_funptr(...)

This is a C null function pointer.

## 5 Type Definitions

  TYPE c_funptr
PRIVATE
...
END TYPE

This type represents a C function pointer, and is used when passing procedure arguments to a C routine. The interface to the C routine is declared with a TYPE(c_funptr) dummy argument, and values of this type can be created by using the function c_funloc on a procedure name (see below for restrictions).

  TYPE c_ptr
PRIVATE
...
END TYPE

This type represents a ‘(void *)’ C data pointer, and is used when passing pointer arguments to a C routine. The interface to the C routine is declared with a TYPE(c_ptr) dummy argument; values of this type are created using the c_loc function (Fortran) pointer or target (see below for restrictions). A C pointer can be turned into a Fortran pointer using the c_f_pointer function (see below for the full description).

## 6 Procedure Descriptions

All the procedures provided are generic and not specific. The c_associated and c_sizeof functions are pure.

In the descriptions below, TYPE(*) means any type (including intrinsic types), and INTEGER(*) means any kind of INTEGER type.

INTERFACE c_associated
PURE LOGICAL FUNCTION c_associated...(c_ptr_1,c_ptr_2) ! Specific name not visible
TYPE(c_ptr),INTENT(IN) :: c_ptr_1,c_ptr_2
OPTIONAL c_ptr_2
END
PURE LOGICAL FUNCTION c_associated...(c_ptr_1,c_ptr_2) ! Specific name not visible
TYPE(c_funptr),INTENT(IN):: c_ptr_1,c_ptr_2
OPTIONAL c_ptr_2
END
END INTERFACE

Returns true if and only if c_ptr_1 is not a null pointer and, if c_ptr_2 is present, the same as c_ptr_2.

INTERFACE c_f_pointer
SUBROUTINE c_f_pointer...(cptr,fptr) ! Specific name not visible
TYPE(c_ptr),INTENT(IN) :: cptr
TYPE(*),INTENT(OUT),POINTER :: fptr
END
SUBROUTINE c_f_pointer...(cptr,fptr,shape) ! Specific name not visible
TYPE(c_ptr),INTENT(IN) :: cptr
TYPE(*),INTENT(OUT),POINTER :: fptr(...)
INTEGER(*),INTENT(IN) :: shape(:)
END
END INTERFACE

Converts a C address to a Fortran pointer. If fptr is an array, shape must be an array whose size is equal to the rank of fptr.

INTERFACE c_f_procpointer
...
END INTERFACE

This procedure is not available in release 5.1. It converts TYPE(c_funptr) into Fortran procedure pointers.

INTERFACE c_funloc
TYPE(c_funptr) FUNCTION c_funloc...(x) ! Specific name not visible
EXTERNAL x
END
END INTERFACE

Returns the C address of a Fortran procedure, which must be a dummy procedure, external procedure or module procedure, and must have the BIND(C) attribute.

Note that since Fortran procedure pointers are not available in release 5.1, invoking a procedure through a TYPE(c_funptr) value can only be done from C.

INTERFACE c_loc
TYPE(c_ptr) FUNCTION c_loc...(x) ! Specific name not visible
TYPE(*),TARGET :: x
END
END INTERFACE

Returns the C address of a Fortran variable, which must have the TARGET attribute and must not be polymorphic (i.e. it must not declared with the CLASS keyword). If x is a pointer, it must be associated with a target; if x is allocatable, it must be allocated with non-zero size. If x is an array, it must have interoperable type and type parameters.

INTERFACE c_sizeof
PURE INTEGER(c_size_t) FUNCTION c_sizeof...(x) ! Specific name not visible
TYPE(*) :: x(..)
END FUNCTION
END INTERFACE


The actual argument x must be interoperable. The result is the same as the C sizeof operator applied to the conceptually corresponding C entity; that is, the size of x in bytes.

For scalars, this will be equal to STORAGE_SIZE(x)/STORAGE_SIZE(C_char_'A'); for an array, the scalar value is multiplied by SIZE(x).