Intel Fortran Language Reference - NCI National Facility

Specification Statements 5
Rules and Behavior
AUTOMATIC and STATIC declarations only affect how data is allocated in storage, as follows:
• A variable declared as AUTOMATIC and allocated in memory resides in the stack storage
area.
• A variable declared as STATIC and allocated in memory resides in the static storage area.
If you want to retain definitions of variables upon reentry to subprograms, you must use the SAVE
attribute.
Automatic variables can reduce memory use because only the variables currently being used are
allocated to memory.
Automatic variables allow possible recursion. With recursion, a subprogram can call itself
(directly or indirectly), and resulting values are available upon a subsequent call or return to the
subprogram. For recursion to occur, RECURSIVE must be specified in one of the following ways:
• As a keyword in a FUNCTION or SUBROUTINE statement
• As a compiler option
• As an option in an OPTIONS statement
By default, the compiler allocates local variables of non-recursive subprograms, except for
allocatable arrays, in the static storage area. The compiler may choose to allocate a variable in
temporary (stack or register) storage if it notices that the variable is always defined before use.
Appropriate use of the SAVE attribute can prevent compiler warnings if a variable is used before it
is defined.
To change the default for variables, specify them as AUTOMATIC or specify RECURSIVE (in
one of the ways mentioned above).
To override any compiler option that may affect variables, explicitly specify the variables as
AUTOMATIC or STATIC.
NOTE. Variables that are data-initialized, and variables in COMMON and
SAVE statements are always static. This is regardless of whether a compiler
option specifies recursion.
A variable cannot be specified as AUTOMATIC or STATIC more than once in the same scoping
unit.
If the variable is a pointer, AUTOMATIC or STATIC apply only to the pointer itself, not to any
associated target.
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