AUTOMATIC and STATIC attributes (The GNU Fortran Compiler)

#### 5.1.25 `AUTOMATIC` and `STATIC` attributes ¶

With `-fdec-static` GNU Fortran supports the DEC extended attributes `STATIC` and `AUTOMATIC` to provide explicit specification of entity storage. These follow the syntax of the Fortran standard `SAVE` attribute.

`STATIC` is exactly equivalent to `SAVE`, and specifies that an entity should be allocated in static memory. As an example, `STATIC` local variables retain their values across multiple calls to a function.

Entities marked `AUTOMATIC` are stack automatic whenever possible. `AUTOMATIC` is the default for local variables smaller than `-fmax-stack-var-size`, unless `-fno-automatic` is given. This attribute overrides `-fno-automatic`, `-fmax-stack-var-size`, and blanket `SAVE` statements.

Examples:

    subroutine f
      integer, automatic :: i  ! automatic variable
      integer x, y             ! static variables
      save
      ...
    endsubroutine

    subroutine f
      integer a, b, c, x, y, z
      static :: x
      save y
      automatic z, c
      ! a, b, c, and z are automatic
      ! x and y are static
    endsubroutine

    ! Compiled with -fno-automatic
    subroutine f
      integer a, b, c, d
      automatic :: a
      ! a is automatic; b, c, and d are static
    endsubroutine