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.

Notes
This 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:

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 Batch Compiler Options and Their Defaults
Equivalent Batch Compile-Link and Incremental Build Options