Visible to Intel only — GUID: GUID-B425E887-C2CF-4D9B-A355-25B880E53463
Visible to Intel only — GUID: GUID-B425E887-C2CF-4D9B-A355-25B880E53463
Locate Runtime Errors
This topic provides some guidelines for locating the cause of exceptions and runtime errors. Intel® Fortran runtime error messages do not usually indicate the exact source location causing the error.
The following compiler options are related to handling errors and exceptions:
check
traceback
fpe
warn and nowarn
fexceptions (Linux and macOS)
Compilation Diagnostics Options in the IDE (Windows)
Their effects are described in the following sections.
The check Option
This option generates extra code to catch certain conditions at runtime. It lets you specify a keyword to check for specific conditions.
The keyword bounds generates code to perform compile-time and runtime checks on 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.
The keyword uninit generates code for dynamic checks of uninitialized variables. If a variable is read before written, a runtime error routine will be called.
The keywords noformat and nooutput_conversion reduce the severity level of the associated runtime error to allow program continuation.
The keyword pointers generates code to test for disassociated pointers and unallocatable arrays.
The following examples show output messages received when the code was specified using option check[:]pointers.
Examples
The following example shows the message received for an allocatable variable that has not been allocated:
real, allocatable:: a(:) ! ! A is initially unallocated. To allocate, use: ! ! allocate(a(4)) ! ! Because A is unallocated, the next statement will ! issue an error in applications built with "check pointers". ! a=17 print *,a end Output 1: forrtl: severe (408): fort: (8): Attempt to fetch from allocatable variable A when it is not allocated
The following example shows the message received for an unassociated pointer:
real, pointer:: a(:) allocate(a(5)) a=17 print *,a deallocate(a) ! Once A is deallocated, the next statement ! issues an error in an application built ! with "check pointers". a=20 print *,a end Output 2: 17.00000 17.00000 17.00000 17.00000 17.00000 forrtl: severe (408): fort: (7): Attempt to use pointer A when it is not associated with a target
The following example shows the message received for a Cray pointer with a zero value:
pointer(p,a) real, target:: b ! ! P initially has no address assigned to it. To assign an ! address, use: ! ! p=loc(b) ! ! Because P has no address assigned to it, the next ! statement will issue an error in an application built ! with "check pointers". ! b=17. print *,a end Output 3: forrtl: severe (408): fort: (9): Attempt to use pointee A when its corresponding integer pointer P has the value zero
The traceback Option
This option generates extra information in the object file to provide source file traceback information when a severe error occurs at runtime. This simplifies the task of locating the cause of severe runtime errors.
Without the traceback option, you could try to locate the cause of the error using a map file and the hexadecimal addresses of the stack displayed when a severe error occurs. Certain traceback-related information accompanies severe runtime errors, as described in Traceback.
The fpe Option
This option controls the handling of floating-point arithmetic exceptions (IEEE arithmetic) at runtime. If you specify the fpe[:]3 compiler option, all floating-point exceptions are disabled, allowing IEEE exceptional values and program continuation.
In contrast, specifying fpe[:]0 stops execution when an exceptional value (such as a NaN) is generated, when floating overflow or divide by zero occur, or when attempting to use a subnormal number, which usually allows you to localize the cause of the error. It also forces underflow to zero.
The warn and nowarn Options
These options control compile-time warning messages, which, in some circumstances, can help determine the cause of a runtime error.
Linux and macOS fexceptions Option
This option enables C++ exception handling table generation, preventing Fortran routines in mixed-language applications from interfering with exception handling between C++ routines.
Windows Compilation Diagnostics Options in the IDE
The Compilation Diagnostics Options in the IDE control compile-time diagnostic messages. In some circumstances, these messages can help determine the cause of a runtime error.