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 Code Example

This code may produce a domain error if the argument is not in the range \[-1, \+1\].

float x, result;

result = acos(x);

Compliant Solution

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

float x, result;

if ( islessequal(x,-1) || isgreaterequal(x, 1) ){
     /* handle domain error */
}

result = acos(x);

atan2( y, x )

Non-Compliant Code Example

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

float x, y, result;

result = atan2(y, x);

Compliant Solution

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

float x, y, result;

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

result = atan2(y, x);

log( x ), log10( x )

Non-Compliant Code Example

This code may produce a domain error if x is negative and a range error if x is zero.

float result, x;

result = log(x);

Compliant Solution

This code tests the suspect arguments to ensure no domain or range errors are raised.

float result, x;

if (islessequal(x, 0)){
     /* handle domain and range errors */
}

result = log(x);

pow( x, y )

Non-Compliant Code Example

This 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

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

float x, y, result;

if (fpclassify(x) == FP_ZERO && islessequal(y, 0)){
     /* handle domain error condition */
}

result = pow(x, y);

sqrt( x )

Non-Compliant Code Example

This code may produce a domain error if x is negative.

float x, result;

result = sqrt(x);

Compliant Solution

This code tests the suspect argument to ensure no domain error is raised.

float x, result;

if (isless(x, 0)){
     /* handle domain error */
}

result = sqrt(x);

Risk Assessment

Failure to properly verify arguments supplied to math functions may result in unexpected results.

Related Vulnerabilities

Search for vulnerabilities resulting from the violation of this rule on the CERT website.

References

\[[ISO/IEC 9899-1999|AA. C References#ISO/IEC 9899-1999]\] Section 7.12, "Mathematics <math.h>"
\[[Plum 91|AA. C References#Plum 91]\] Topic 2.10, "conv - conversions and overflow"