Command-Line Mode Control: The +FP Compiler Option

The compiler and linker option +FP allows you to specify what traps to enable for your program and can also enable or disable flush-to-zero mode. This option is available with the HP Fortran, C, and Pascal compilers. It has the following syntax:

+FPflags

where flags is a series of uppercase or lowercase letters from the set [VvZzOoUuIiDd] with no spaces, tabs, or other characters between them. If the uppercase letter is selected, that behavior is enabled. If the lowercase letter is selected or if the letter is not present in the flags, the behavior is disabled. By default, all traps are disabled.

Table 5-3 “+FP Option Arguments” describes the behavior specified by each argument.

For example, the following command line sets traps for overflow, divide by zero, and invalid operations, and enables fast underflow mode:

f77 +FPOZVD program_name.f

The linker (ld) also accepts the +FP option. If you specify this option to a separately invoked ld command, the option is effective only if you link in one of the supported startup files (/opt/langtools/lib/*crt0.o).

The +FP option affects the various floating-point mode settings at program startup. Subsequent calls to fesettrapenable, fesetflushtozero, ­or fpsetenv may override some or all of the values set by +FP.

	NOTE: If you use Fortran, you may also use the +fp_exception (Fortran 90) or +T (HP FORTRAN/9000) option to set traps at compile time. (If your HP FORTRAN/9000 program contains an ON statement, you must use this option.) These options enable traps for invalid operation, overflow, underflow, and division by zero exceptions. If you specify both +FP and +fp_exception (or +T), the +fp_exception (or +T) option is always processed after +FP. It does not turn off any bits set by +FP, however.

See “Using the +FP Compiler Option” for more information on using the +FP option.