Special Considerations

Here are some special considerations when working with pointers and memory allocation with malloc(), loc(), and free():

• The pointers are of type integer, and are automatically typed that way by the compiler. You must not type them yourself.

• A pointer-based variable cannot itself be a pointer.

• The pointer-based variables can be of any type, including structures.

• No storage is allocated when such a pointer-based variable is declared, even if there is a size specification in the type statement.

• You cannot use a pointer-based variable as a dummy argument or in COMMON, EQUIVALENCE, DATA, or NAMELIST statements.

• The dimension expressions for pointer-based variables must be constant expressions in main programs. In subroutines and functions, the same rules apply for pointer-based array variables as for dummy arguments--the expression can contain dummy arguments and variables in common. Any variables in the expressions must be defined with an integer value at the time the subroutine or function is called.

• Address expressions cannot exceed the range of INTEGER*4 on 32-bit environments. If the expression is not in the range (-2147483648, 2147483647), then the results are unpredictable.

• When compiling for 64-bit environments, use malloc64() to access the 64-bit address space. Routine malloc64() takes an INTEGER*8 argument and returns a 64-bit pointer value. In 64-bit programs, pointers defined by the POINTER statement are 64-bit INTEGER*8 values. See the Fortran Library Reference Manual and the malloc(3F) man pages.