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It is implementation-defined whether the specifier int designates the same type as signed int or the same type as unsigned int for bit fields. According to the C standard [ISO/IEC 9899:2011], C integer promotions also require that "if an int can represent all values of the original type (as restricted by the width, for a bit-field), the value is converted to an int; otherwise, it is converted to an unsigned int."
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CERT C++ Secure Coding Standard: INT12-CPP. Do not make assumptions about the type of a plain int bit-field when used in an expression
ISO/IEC 9899:2011 Section Section 6.3.1.1, "Boolean, characters, and integers," and Section 6.7.2, "Type specifiers"
ISO/IEC TR 24772 "STR Bit Representationsrepresentations"
MISRA Rule 12.7
Bibliography
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