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• Operations on two compile-time constants
• Operations on a variable and 0 (except divison by 0, of course)
• Subtracting any variable from its type's maximum. For instance, any unsigned int may safely be subtracted from INTUINT_MAX.
• Multiplying any variable by 0 or 1
• Division, as long as the divisor is nonzero.
• Left-shifting 0 by any number.
• Right-shifting any type maximum by any number smaller than the type size. For instance, INTUINT_MAX >> x is valid as long as x < sizeof( int).

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Fortify SCA Version 5.0 with the CERT C Rule Pack can detect violations of this rule.

Compass/ROSE can detect violations of this rule by ensuring that operations are checked for overflow before being performed. Be mindful of INT32-EX2, as it excuses many operations from requiring validation; including all the operations that would validate a potentially dangerous operation. For instnace, adding two unsigned int}}s together requires validation involving subtracting one of the numbers from {{UINT_MAX, which itself requires no validation, as it cannot wrap.

Related Vulnerabilities

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

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