Prevent math errors by carefully bounds-checking before calling functions. In particular, the following domain errors should be prevented by prior bounds-checking:

The calling function should take alternative action if these bounds are violated.

acos(x), asin(x)

Non-Compliant Example

The following code may produce a domain error if the argument is not in the range -1, +1.

float x, result;

result = acos(x);

Compliant Example

The following code uses bounds checking to ensure there is not a domain error.

float x, result;

if( x <= -1 || x >= 1){
     /* handle domain error */
}

result = acos(x);

atan2

Non-Compliant Solution

The following code may produce a domain error if both x and y are zero.

float x, y, result;

result = atan2(y, x);

Compliant Solution

The following code tests the arguments to ensure that there is not a domain error.

float x, y, result;

if( x == 0 && y == 0){
     /* handle domain error */
}

result = atan2(y, x);

pow(x,y)

Non-Compliant Example

The following code may produce a domain error if x is zero and y less than or equal to zero. A range error may also occur if x is zero and y is negative.

float x, y, result;

result = pow(x,y);

Compliant Solution

The following code tests x and y to ensure that there will be no range or domain errors.

float x, y, result;

if(x == 0 && y <=0){
     /* handle domain error condition */
}

result = pow(x, y);

References

• ISO/IEC 9899-1999 7.12 Mathematics <math.h>
• Plum 91 Topic: 2.10 conv - conversions and overflow