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When a value of real floating type is converted to a real floating type, if the value being converted can be represented exactly in the new type, it is unchanged.

When a value of real floating type is converted to a standard floating type, if the value being converted is in the range of values that can be represented but cannot be represented exactly, the result is either the nearest higher or nearest lower representable value, chosen in an implementation-defined manner. If the value being converted is outside the range of values that can be represented, the behavior is undefined. 

See undefined behaviors 16 and 17 and 18.

This rule does not apply to demotions of floating-point types on implementations that support signed infinity, such as IEEE 754, as all values are within range.

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This noncompliant code example leads to to undefined behavior if 16 if the integral part of f_a cannot be represented as an integer:

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As a result of these conversions, it is possible that d_a is outside the range of values that can be represented by a float or that big_d is outside the range of values that can be represented as either a float or a double. If this is the case, the result is is undefined on behavior 17 on implementations that do not support Annex F, "IEC 60559 Floating-Point Arithmetic."

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Converting a floating-point value to a floating-point value of a smaller range and precision or to an integer type, or converting an integer type to a floating-point type, can result in a value that is not representable in the destination type and is undefined behavior on implementations that do not support Annex F.

Automated Detection

Related Vulnerabilities

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

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