XL Fortran Enterprise Edition for AIX : User's Guide - IBM

-qflttrap Option
Syntax
-qflttrap[=suboptions] | -qnoflttrap
FLTTRAP[(suboptions)] | NOFLTTRAP
Determines what types of floating-point exception conditions to detect at run time.
The program receives a SIGTRAP signal when the corresponding exception
occurs.
Arguments
ENable
IMPrecise
INEXact
INValid
NANQ
OVerflow
UNDerflow
ZEROdivide
Turn on checking for the specified exceptions in the main program
so that the exceptions generate SIGTRAP signals. You must specify
this suboption if you want to turn on exception trapping without
modifying your source code.
Only check for the specified exceptions on subprogram entry and
exit. This suboption improves performance, but it can make the
exact spot of the exception difficult to find.
Detect and trap on floating-point inexact if exception-checking is
enabled. Because inexact results are very common in floating-point
calculations, you usually should not need to turn this type of
exception on.
Detect and trap on floating-point invalid operations if
exception-checking is enabled.
Detect and trap all quiet not-a-number values (NaNQs) and
signaling not-a-number values (NaNSs). Trapping code is
generated regardless of specifying the enable or imprecise
suboption. This suboption detects all NaN values handled by or
generated by floating point instructions, including those not
created by invalid operations. This option can impact performance.
Detect and trap on floating-point overflow if exception-checking is
enabled.
Detect and trap on floating-point underflow if exception-checking
is enabled.
Detect and trap on floating-point division by zero if
exception-checking is enabled.
Defaults
The -qflttrap option without suboptions is equivalent to
-qflttrap=ov:und:zero:inv:inex. However, because this default does not include
enable, it is probably only useful if you already use fpsets or similar subroutines
in your source. If you specify -qflttrap more than once, both with and without
suboptions, the -qflttrap without suboptions is ignored.
Restrictions
On AIX Version 5.1 and above, if you use -qflttrap=inv:en to compile a program
containing an IEEE invalid SQRT operation and then run that program, the
expected SIGTRAP signal may not occur on PowerPC machines and does not
occur at all on POWER machines.
You can only fix this problem for AIX Version 5.1 and subsequent levels of the
operating system. Specify the following command:
XL Fortran Compiler-Option Reference 165