Is Right Shifting an Unsigned Integer with a Count Exceeding its Type Width Undefined Behavior in C ?

Undefined Behavior of Right Shift with Count Exceeding Type Width

In C , the behavior of the right shift operator (>>) is defined in the standard, specifically in section 5.8, Shift operators. The question arises whether a shift count that is greater than or equal to the width of the type of the left operand is undefined behavior.

The C standard states that the value of E1 >> E2 is the integral part of the quotient of E1/2^E2, where E1 is the left operand and E2 is the right operand. This implies that the behavior is only defined if E1 has an unsigned type or a signed type with a non-negative value and E2 is non-negative.

However, the question considers the case where E1 is of type unsigned int and E2 is 34, which exceeds the width of 32 bits for an unsigned int. The standard explicitly states that the behavior in this case is undefined.

Therefore, despite the statement in the C standard regarding the quotient calculation, the behavior of right shifting an unsigned int with a count greater than 32 is undefined. This is why GCC issues a warning when performing such a shift.

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