If the size of executable is critical to your application, you can use the +stripoption to remove symbol table information from the production version of your program. If you compile and link on separate command lines, you must use the +stripoption on both command lines. Instead of recompiling with +strip, you can use the strip utility, which removes all debugging information, including the symbol table.

If the size of your executable is not important, you may want to retain the symbol table in the production version of your program. This table can be used by the debugger to provide minimal debugging. If a program has not been compiled with -g and does not include a symbol table, it is unusable by the debugger. Also, without the information provided by the symbol table, a procedure traceback displays virtual addresses only.

The amount of code that the symbol table information that adds to an executable is considerably less than the amount that compiling with -g adds. For descriptions of the -gand +strip options, see the HP Fortran Programmer’s Reference. For information about the strip utility, refer to thestrip(1) man page.

Handling runtime exceptions

Broadly defined, an exception is an error or fault condition that affects a program’s results. Exceptions can range from the relatively begin in exact result condition that occurs in certain floating-point operations to the more severe segmentation violation that occurs when a runaway program attempts to access unallocated memory.

Exceptions that threaten the integrity of the operating system can cause HP-UX to raise an exception signal (for example, SIGSEGV for a segmentation violation) so that the process can take appropriate action to recover from the exception. Such exceptions may cause the program that took the exception to abort, but not necessarily. By trapping an exception—that is, by catching the signal—a program may handle the exception, if only by aborting when it occurs.

There are also a well-defined set of floating-point conditions that, although they pose no threat to the operating system, can also cause an exception—for example, dividing a floating-point number by zero. By default, traps for floating-point exceptions are disabled on HP9000 computers, but they can be enabled by +fp_exceptionand +FPoptions. (You can also use the ON statement to enable traps for floating-point exceptions.)

Programs that have been compiled with the +fp_exception option can trap the exceptions listed in Table4-1. Any of the exceptions listed in the second column will cause the operating system to generate the signal listed in the first column. Programs compiled with +FP can trap specific floating-point exceptions (SIGFPE).

Table 25 Signals recognized by +fp_exception

Signal

Exception

 

 

SIGBUS

Bus error instruction

 

 

SIGFPE

Floating-point exceptions

 

 

SIGILL

Illegal instruction

 

 

SIGSEGV

Segmentation violation or memory fault

 

 

SIGSYS

Bad argument to a kernel system call

 

 

When a program compiled with +fp_exception takes an exception, the following events occur:

•The program traps the exception.

•A procedure traceback is displayed on standard error. A procedure traceback lists routine names and their offsets that are helpful in locating the code that triggered the exception.

•The program aborts.

Handling runtime exceptions 77