The GNU Fortran Compiler: ISO_C_BINDING

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### 10.2 `ISO_C_BINDING`

Standard:

  Fortran 2003 and later, GNU extensions

The following intrinsic procedures are provided by the module; their definition can be found in the section Intrinsic Procedures of this manual.

`C_ASSOCIATED`
`C_F_POINTER`
`C_F_PROCPOINTER`
`C_FUNLOC`
`C_LOC`
`C_SIZEOF`

The `ISO_C_BINDING` module provides the following named constants of type default integer, which can be used as KIND type parameters.

In addition to the integer named constants required by the Fortran 2003 standard and `C_PTRDIFF_T` of TS 29113, GNU Fortran provides as an extension named constants for the 128-bit integer types supported by the C compiler: `C_INT128_T, C_INT_LEAST128_T, C_INT_FAST128_T`. Furthermore, if `__float128` is supported in C, the named constants `C_FLOAT128, C_FLOAT128_COMPLEX` are defined.

Fortran Type | Named constant | C type | Extension
`INTEGER` | `C_INT` | `int`
`INTEGER` | `C_SHORT` | `short int`
`INTEGER` | `C_LONG` | `long int`
`INTEGER` | `C_LONG_LONG` | `long long int`
`INTEGER` | `C_SIGNED_CHAR` | `signed char`/`unsigned char`
`INTEGER` | `C_SIZE_T` | `size_t`
`INTEGER` | `C_INT8_T` | `int8_t`
`INTEGER` | `C_INT16_T` | `int16_t`
`INTEGER` | `C_INT32_T` | `int32_t`
`INTEGER` | `C_INT64_T` | `int64_t`
`INTEGER` | `C_INT128_T` | `int128_t` | Ext.
`INTEGER` | `C_INT_LEAST8_T` | `int_least8_t`
`INTEGER` | `C_INT_LEAST16_T` | `int_least16_t`
`INTEGER` | `C_INT_LEAST32_T` | `int_least32_t`
`INTEGER` | `C_INT_LEAST64_T` | `int_least64_t`
`INTEGER` | `C_INT_LEAST128_T` | `int_least128_t` | Ext.
`INTEGER` | `C_INT_FAST8_T` | `int_fast8_t`
`INTEGER` | `C_INT_FAST16_T` | `int_fast16_t`
`INTEGER` | `C_INT_FAST32_T` | `int_fast32_t`
`INTEGER` | `C_INT_FAST64_T` | `int_fast64_t`
`INTEGER` | `C_INT_FAST128_T` | `int_fast128_t` | Ext.
`INTEGER` | `C_INTMAX_T` | `intmax_t`
`INTEGER` | `C_INTPTR_T` | `intptr_t`
`INTEGER` | `C_PTRDIFF_T` | `intptr_t` | TS 29113
`REAL` | `C_FLOAT` | `float`
`REAL` | `C_DOUBLE` | `double`
`REAL` | `C_LONG_DOUBLE` | `long double`
`REAL` | `C_FLOAT128` | `__float128` | Ext.
`COMPLEX` | `C_FLOAT_COMPLEX` | `float _Complex`
`COMPLEX` | `C_DOUBLE_COMPLEX` | `double _Complex`
`COMPLEX` | `C_LONG_DOUBLE_COMPLEX` | `long double _Complex`
`REAL` | `C_FLOAT128_COMPLEX` | `__float128 _Complex` | Ext.
`LOGICAL` | `C_BOOL` | `_Bool`
`CHARACTER` | `C_CHAR` | `char`

Additionally, the following parameters of type `CHARACTER(KIND=C_CHAR)` are defined.

Name | C definition | Value
`C_NULL_CHAR` | null character | `'\0'`
`C_ALERT` | alert | `'\a'`
`C_BACKSPACE` | backspace | `'\b'`
`C_FORM_FEED` | form feed | `'\f'`
`C_NEW_LINE` | new line | `'\n'`
`C_CARRIAGE_RETURN` | carriage return | `'\r'`
`C_HORIZONTAL_TAB` | horizontal tab | `'\t'`
`C_VERTICAL_TAB` | vertical tab | `'\v'`

Moreover, the following two named constants are defined:

Name | Type
`C_NULL_PTR` | `C_PTR`
`C_NULL_FUNPTR` | `C_FUNPTR`

Both are equivalent to the value `NULL` in C.

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