flttrap

Option Type	Default Value	#pragma options	C	C++
-qoption	noflttrap	FLTTRAP	x	x

Syntax:

    -qflttrap | -qflttrap=suboptions | -qnoflttrap 
    FLTTRAP | FLTTRAP=suboptions | NOFLTTRAP

Purpose Generates extra instructions to detect and trap floating-point exceptions.

NotesThis option is recognized during linking. -qnoflttrap specifies that these extra instructions need not be generated.

If specified with #pragma options, the -qnoflttrap option must be the first option specified.

The flttrap option has the following suboptions:

`OVerflow`	Generates code to detect and trap floating-point overflow.
`UNDerflow`	Generates code to detect and trap floating-point underflow.
`ZEROdivide`	Generates code to detect and trap floating-point division by zero.
`INValid`	Generates code to detect and trap floating-point invalid operation exceptions.
`INEXact`	Generates code to detect and trap floating-point inexact exceptions.
`ENable`	Enables the specified exceptions in the prologue of the main program. This suboption is required if you want to turn on exception trapping without modifying the source code.
`IMPrecise`	Generates code for imprecise detection of the specified exceptions. If an exception occurs, it is detected, but the exact location of the exception is not determined.

Specifying the flttrap option with no suboptions is equivalent to setting -qflttrap=ov:und:zero:inv:inex. The exceptions are not automatically enabled, and all floating-point operations are checked to provide precise exception-location information.

If your program contains signalling NaNs, you should use the -qfloat=nans along with -qflttrap to trap any exceptions.

The compiler exhibits behavior as illustrated in the following examples when the -qflttrap option is specified together with -qoptimize options:

with -O:
- 1/0 generates a div0 exception and has a result of infinity
- 0/0 generates an invalid operation
with -O3:
- 1/0 generates a div0 exception and has a result of infinity
- 0/0 returns zero multiplied by the result of the previous division.

Example
To compile myprogram.c so that floating-point overflow and underflow and divide by zero are detected, enter:

    xlC myprogram.c -qflttrap=overflow:underflow:zerodivide:enable

RISC System/6000 Floating Point Hardware

List of Compiler Options and Their Defaults