CERT C++: FLP32-C

Invalid use of standard library floating point routine occurs when you use invalid arguments with a floating point function from the standard library. This defect picks up:

Domain errors on standard library floating point functions result in implementation-defined values. If you use the function return value in subsequent computations, you can see unexpected results.

The fix depends on the root cause of the defect. Often the result details show a sequence of events that led to the defect. Use this event list to determine how the function argument acquires invalid values. You can implement the fix on any event in the sequence. If the result details do not show the event history, you can trace back using right-click options in the source code and see previous related events. See also Interpret Bug Finder Results in Polyspace Desktop User Interface.

It is a good practice to handle for domain errors before using a standard library floating point function. For instance, before calling the acos function, check if the argument is in [-1.0, 1.0] and handle the error.

See examples of fixes below.

If you do not want to fix the issue, for instance, when you handle infinities in your code, add comments to your result or code to avoid another review. See:

By default, a Bug Finder analysis does not recognize infinities and NaNs. Operations that results in infinities and NaNs might be flagged as defects. To handle infinities and NaN values in your code, use the option Consider non finite floats (-allow-non-finite-floats).

#include <math.h>

double arccosine(void) {
    double degree = 5.0;
    return acos(degree); //Noncompliant
}

The input value to acos must be in the interval [-1,1]. This input argument, degree, is outside this range.

One possible correction is to change the input value to fit the specified range. In this example, change the input value from degrees to radians to fix this defect.

#include <math.h>

double arccosine(void) {
    double degree = 5.0;
    double radian = degree * 3.14159 / 180.;
    return acos(radian);
}