# auto

Causes all local, non-SAVEd variables to be allocated to the run-time stack.

## Syntax

Linux: | -auto -noauto

macOS: | -auto -noauto

Windows: | /auto /noauto

## Arguments

None

## Default

-auto-scalar or /Qauto-scalar | Scalar variables of intrinsic types INTEGER, REAL, COMPLEX, and LOGICAL are allocated to the run-time stack. Note that the default changes to option auto if one of the following options are specified: recursive [q or Q]openmp

## Description

This option places local variables (scalars and arrays of all types), except those declared as SAVE, on the run-time stack. It is as if the variables were declared with the AUTOMATIC attribute.

It does not affect variables that have the SAVE attribute or ALLOCATABLE attribute, or variables that appear in an EQUIVALENCE statement or in a common block.

This option may provide a performance gain for your program, but if your program depends on variables having the same value as the last time the routine was invoked, your program may not function properly.

If you want to cause variables to be placed in static memory, specify option [Q]save. If you want only scalar variables of certain intrinsic types to be placed on the run-time stack, specify option auto-scalar.

### Note

On Windows NT* systems, there is a performance penalty for addressing a stack frame that is too large. This penalty may be incurred with /[Q]auto, because arrays are allocated on the stack along with scalars. However, with /Qauto-scalar, you would have to have more than 32K bytes of local scalar variables before you incurred the performance penalty. /Qauto-scalar enables the compiler to make better choices about which variables should be kept in registers during program execution.

## IDE Equivalent

Visual Studio: Data > Local Variable Storage

## Alternate Options

auto | Linux and macOS: None Windows: /Qauto, /4Ya
noauto | Linux and macOS: -save Windows: /Qsave, /4Na

Parent topic: Data Options

## See Also

auto-scalar, Qauto-scalar compiler option
save, Qsave compiler option