Handling Integer Exceptions

Handling Integer Division by Zero

Trapping on integer division by zero is enabled by default for both Fortran and C. The trap generates a SIGFPE error. This error may be confusing, because the error is really an integer error, and you cannot disable or enable it by manipulating the floating-point status register (for example, by using +FP or fesettrapenable).

If for some reason you wish to disable the trap, you can do so in Fortran by using an ON INTEGER DIV 0 IGNORE statement. You cannot disable the trap in C.

If you want to establish a handler for an integer division by zero, you can do so using either of the mechanisms described in “Handling Traps”: the C sigaction(2) function or the Fortran ON statement.

Handling Integer Overflow

Trapping on integer overflow is disabled by default for Fortran and C; an integer overflow does not generate a SIGFPE error. Detecting integer overflows requires not only that the trap be enabled but also that the compiler insert special code in the executable file to check for overflows.

To enable integer overflow checking for Fortran, use a !$HP$ CHECK_OVERFLOW ON directive (in HP Fortran/9000, use $CHECK_OVERFLOW INTEGER_4 or INTEGER_2) to obtain the overflow checking code, and use an ON INTEGER OVERFLOW statement to handle the trap. (The !$HP$ CHECK_OVERFLOW directive does not enable checking for operations in libraries. Using the exponentiation operator involves a library call in HP Fortran, so it is not possible to enable integer overflow checking for exponentiation operations.)

There is no way to enable integer overflow checking in C. HP C provides no mechanism to insert overflow checking code into your executable, because the C language does not define integer overflow as an error.