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The result of E1 << E2 is E1 left-shifted E2 bit positions; vacated bits are filled with zeros. If E1 has a signed type and nonnegative value, and E1 * 2 E2 is representable in the result type, then that is the resulting value; otherwise, the behavior is undefined.

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The following code can result in undefined behavior because there is no check to ensure that left and right operands have nonnegative values, and that the right operand is greater than or equal to the width of the promoted left operand.

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The result of E1 >> E2 is E1 right-shifted E2 bit positions. If E1 has an unsigned type or if E1 has a signed type and a nonnegative value, the value of the result is the integral part of the quotient of E1 / 2 E2. If E1 has a signed type and a negative value, the resulting value is implementation-defined.

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This non-compliant code example fails to prevent undefined behavior.

int si1, si2, sresult;
unsigned int ui1, ui2, uresult;

sresult = si1 >> si2;
uresult = ui1 >> ui2;

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