F77_IEEE_ENVIRONMENT(3F)

NAME

f77_ieee_environment − mode, status, and signal handling for IEEE arithmetic

SYNOPSIS

#include <f77/f77_floatingpoint.h>

integer∗4 function ieee_flags(action,mode,in,out)
character∗(∗) action, mode, in, out

integer∗4 function ieee_handler(action,exception,hdl)
character∗(∗) action, exception
sigfpe_handler_type hdl

sigfpe_handler_type function sigfpe(code, hdl)
sigfpe_code_type code
sigfpe_handler_type hdl

DESCRIPTION

These subprograms provide modes and status required to fully exploit ANSI/IEEE Standard 754-1985 arithmetic in a FORTRAN program. They correspond closely to the functions ieee_flags(3M), ieee_handler(3M), and sigfpe(3).

USAGE

Example 1: Set rounding direction to round toward zero, unless the hardware does not support directed rounding modes:

integer∗4 ieeer
character∗1 mode, out, in
ieeer = ieee_flags(’set’, ’direction’, ’tozero’, out)

Example 2: Clear rounding direction to default, round toward nearest:

character∗1 out, in
ieeer = ieee_flags(’clear’,’direction’, in, out)

Example 3: Clear all accrued exception-occurred bits:

character∗16 out
ieeer = ieee_flags(’clear’,’exception’,’all’,out)

Example 4: If example 3 generates the overflow exception, detect the exception as follows:

character∗16 out
ieeer = ieee_flags(’get’,’exception’,’overflow’, out)

Example 5: A user-specified signal handler, with a main program to use it:

external hand
real r / 14.2 /, s / 0.0 /
i = ieee_handler( ’set’, ’division’, hand )
t = r/s
end
integer function hand ( sig, sip, uap )
integer sig, address
structure /fault/
integer address
end structure
structure /siginfo/
integer si_signo
integer si_code
integer si_errno
record /fault/ fault
end structure
record /siginfo/ sip
address = sip.fault.address
write (∗,10) address
10format(’Exception at hex address ’, z8 )
end

FILES

include/f77/f77_floatingpoint.h
libm.a

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