# check

Checks for certain conditions at run time.

## Syntax

Linux: | -check [keyword[, keyword...]] -nocheck

macOS: | -check [keyword[, keyword...]] -nocheck

Windows: | /check[:keyword[, keyword...]] /nocheck

## Arguments

keyword | Specifies the conditions to check. Possible values are:
none | Disables all check options.
[no]arg_temp_created | Determines whether checking occurs for actual arguments copied into temporary storage before routine calls.
[no]assume | Determines whether checking occurs to test that the scalar-Boolean-expression in the ASSUME directive is true, or that the addresses in the ASSUME_ALIGNED directive are aligned on the specified byte boundaries.
[no]bounds | Determines whether checking occurs for array subscript and character substring expressions.
[no]contiguous | Determines whether the compiler checks pointer contiguity at pointer-assignment time.
[no]format | Determines whether checking occurs for the data type of an item being formatted for output.
[no]output_conversion | Determines whether checking occurs for the fit of data items within a designated format descriptor field.
[no]pointers | Determines whether checking occurs for certain disassociated or uninitialized pointers or unallocated allocatable objects.
[no]shape | Determines whether array conformance checking is performed.
[no]stack | Determines whether checking occurs on the stack frame.
[no]teams | Determines whether the run-time system diagnoses non-standard coarray team usage.
[no]udio_iostat | Determines whether conformance checking occurs when user-defined derived type input/output routines are executed.
[no]uninit | Determines whether checking occurs for uninitialized variables.
all | Enables all check options.

## Default

nocheck | No checking is performed for run-time failures. Note that if option vms is specified, the defaults are check format and check output_conversion.

## Description

This option checks for certain conditions at run time.

Option | Description
--- | ---
check none | Disables all check options (same as nocheck).
check arg_temp_created | Enables run-time checking on whether actual arguments are copied into temporary storage before routine calls. If a copy is made at run-time, an informative message is displayed.
check assume | Enables run-time checking on whether the scalar-Boolean-expression in the ASSUME directive is true and that the addresses in the ASSUME_ALIGNED directive are aligned on the specified byte boundaries. If the test is .FALSE., a run-time error is reported and the execution terminates.
check bounds | Enables compile-time and run-time checking for array subscript and character substring expressions. An error is reported if the expression is outside the dimension of the array or the length of the string. For array bounds, each individual dimension is checked. For arrays that are dummy arguments, only the lower bound is checked for a dimension whose upper bound is specified as * or where the upper and lower bounds are both 1. For some intrinsics that specify a DIM= dimension argument, such as LBOUND, an error is reported if the specified dimension is outside the declared rank of the array being operated upon. Once the program is debugged, omit this option to reduce executable program size and slightly improve run-time performance. It is recommended that you do bounds checking on unoptimized code. If you use option check bounds on optimized code, it may produce misleading messages because registers (not memory locations) are used for bounds values.
check contiguous | Tells the compiler to check pointer contiguity at pointer-assignment time. This will help prevent programming errors such as assigning contiguous pointers to non-contiguous objects.
check format | Issues the run-time FORVARMIS fatal error when the data type of an item being formatted for output does not match the format descriptor being used (for example, a REAL*4 item formatted with an I edit descriptor). With check noformat, the data item is formatted using the specified descriptor unless the length of the item cannot accommodate the descriptor (for example, it is still an error to pass an INTEGER*2 item to an E edit descriptor).
check output_conversion | Issues the run-time OUTCONERR continuable error message when a data item is too large to fit in a designated format descriptor field without loss of significant digits. Format truncation occurs, the field is filled with asterisks (*), and execution continues.
check pointers | Enables run-time checking for disassociated or uninitialized Fortran pointers, unallocated allocatable objects, and integer pointers that are uninitialized.
check shape | Enables compile-time and run-time array conformance checking in contexts where it is required by the standard. These include the right-hand and left-hand side of intrinsic and elemental defined assignment, the operands of intrinsic and elemental defined binary operations, two or more array arguments to ELEMENTAL procedures, the ARRAY= and MASK= arguments to intrinsic procedures as required, and the arguments to the intrinsic module procedures IEEE_SET_FLAG and IEEE_SET_HALTING_MODE. In an ALLOCATE statement with array bounds specified for an allocate-object and with SOURCE=source specified, the allocate-object must conform with source. Note that you can specify a setting in the warn option to choose whether array conformance violations are diagnosed with errors or warnings.
check stack | Enables checking on the stack frame. The stack is checked for buffer overruns and buffer underruns. This option also enforces local variables initialization and stack pointer verification. This option disables optimization and overrides any optimization level set by option O.
check stack | Enables checking on the stack frame. The stack is checked for buffer overruns and buffer underruns. This option also enforces local variables initialization and stack pointer verification. This option disables optimization and overrides any optimization level set by option O.
check teams | Enables checking for non-standard coarray team usage. For example, ifort permits the TEAM argument to NUM_IMAGES to be a type TEAM_TYPE variable which describes a team that is not the current or an ancestor of the current team. Similarly, ifort permits the TEAM_NUMBER specifier in an image selector to specify a value of -1 indicating the initial team. Such behavior is not permitted by the standard. When check teams is specified, a message is generated each time a non-standard coarray extension is detected.
check uninit | Enables run-time checking for uninitialized variables. If a variable is read before it is written, a run-time error routine will be called. Only local scalar variables of intrinsic type INTEGER, REAL, COMPLEX, and LOGICAL without the SAVE attribute are checked. To detect uninitialized arrays or array elements, see option [Q]init or see the article titled Detection of Uninitialized Floating-point Variables in Intel® Fortran.
check all | Enables all check options. This is the same as specifying check with no keyword. This option disables optimization and overrides any optimization level set by option O.

To get more detailed location information about where an error occurred, use option traceback.

## IDE Equivalent

Visual Studio: Run-time > Runtime Error Checking (/nocheck, /check:all)

Run-time > Check Array and String Bounds (/check:bounds)

Run-time > Check Uninitialized Variables (/check:uninit)

Run-time > Check Edit Descriptor Data Type (/check:format)

Run-time > Check Edit Descriptor Data Size (/check:output_conversion)

Run-time > Check For Actual Arguments Using Temporary Storage (/check:arg_temp_created)

Run-time > Check Array Conformance (/check:shape)

Run-time > Check For Null Pointers and Allocatable Array References (/check:pointers)

## Alternate Options

check none | Linux and macOS: -nocheck Windows: /nocheck
check bounds | Linux and macOS: -CB Windows: /CB
check shape | Linux and macOS: -CS Windows: /CS
check uninit | Linux and macOS: -CU Windows: /RTCu, /CU
check all | Linux and macOS: -check, -C Windows: /check, /C

Parent topic: Language Options

## See Also

traceback compiler option
init, Qinit compiler option
warn compiler option
ASSUME directive
ASSUME_ALIGNED directive