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RULE-7-0-4 - InappropriateBitwiseOrShiftOperands
Detects inappropriate operands for bitwise and shift operators that violate type requirements. Identifies signed operands in bitwise operations and improper shift operand types that may cause undefined behavior. [a]
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‎cpp/misra/src/rules/RULE-7-0-4/InappropriateBitwiseOrShiftOperands.ql

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/**
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* @id cpp/misra/inappropriate-bitwise-or-shift-operands
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* @name RULE-7-0-4: The operands of bitwise operators and shift operators shall be appropriate
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* @description Bitwise and shift operators should only be applied to operands of appropriate types
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* and values to avoid implementation-defined or undefined behavior.
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* @kind problem
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* @precision very-high
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* @problem.severity error
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* @tags external/misra/id/rule-7-0-4
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* scope/single-translation-unit
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* external/misra/enforcement/decidable
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* external/misra/obligation/required
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*/
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import cpp
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import codingstandards.cpp.misra
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import codingstandards.cpp.misra.BuiltInTypeRules
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predicate isSignedType(NumericType t) { t.getSignedness() = Signed() }
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predicate isUnsignedType(NumericType t) { t.getSignedness() = Unsigned() }
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predicate isConstantExpression(Expr e) {
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e instanceof Literal or
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e.isConstant()
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}
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predicate isValidShiftConstantRange(Expr right, Type leftType) {
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exists(int value |
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value = right.getValue().toInt() and
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value >= 0 and
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value < leftType.getSize() * 8
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)
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}
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predicate isSignedConstantLeftShiftException(LShiftExpr shift) {
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exists(Expr left, Expr right, NumericType leftType, int leftVal, int rightVal, int maxBit |
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left = shift.getLeftOperand() and
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right = shift.getRightOperand() and
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leftType = left.getType() and
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isConstantExpression(left) and
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isConstantExpression(right) and
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isSignedType(leftType) and
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isValidShiftConstantRange(right, leftType) and
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leftVal = left.getValue().toInt() and
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rightVal = right.getValue().toInt() and
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leftVal >= 0 and
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maxBit = leftType.getSize() * 8 - 1 and
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// Check that no set bit is shifted into or beyond the sign bit
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leftVal * 2.pow(rightVal) < 2.pow(maxBit)
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)
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}
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class BinaryShiftOperation extends BinaryOperation {
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BinaryShiftOperation() {
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this instanceof LShiftExpr or
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this instanceof RShiftExpr
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}
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}
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class AssignShiftOperation extends AssignOperation {
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AssignShiftOperation() {
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this instanceof AssignLShiftExpr or
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this instanceof AssignRShiftExpr
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}
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}
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from Expr x, string message
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where
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not isExcluded(x, ConversionsPackage::inappropriateBitwiseOrShiftOperandsQuery()) and
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(
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// Binary bitwise operators (excluding shift operations) - both operands must be unsigned
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exists(BinaryBitwiseOperation op |
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not op instanceof BinaryShiftOperation and
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op = x and
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not (
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isUnsignedType(op.getLeftOperand().getExplicitlyConverted().getType()) and
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isUnsignedType(op.getRightOperand().getExplicitlyConverted().getType())
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) and
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message =
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"Binary bitwise operator '" + op.getOperator() + "' requires both operands to be unsigned."
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)
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or
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// Compound assignment bitwise operators - both operands must be unsigned
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exists(AssignBitwiseOperation op |
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not op instanceof AssignShiftOperation and
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op = x and
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not (
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isUnsignedType(op.getLValue().getExplicitlyConverted().getType()) and
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isUnsignedType(op.getRValue().getExplicitlyConverted().getType())
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) and
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message =
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"Compound assignment bitwise operator '" + op.getOperator() +
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"' requires both operands to be unsigned."
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)
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or
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// Bit complement operator - operand must be unsigned
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exists(ComplementExpr comp |
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comp = x and
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not isUnsignedType(comp.getOperand().getExplicitlyConverted().getType()) and
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message = "Bit complement operator '~' requires unsigned operand."
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)
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or
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// Shift operators - left operand must be unsigned
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exists(BinaryShiftOperation shift |
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shift = x and
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not isUnsignedType(shift.getLeftOperand().getExplicitlyConverted().getType()) and
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not isSignedConstantLeftShiftException(shift) and
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message = "Shift operator '" + shift.getOperator() + "' requires unsigned left operand."
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)
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or
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// Shift operators - right operand must be unsigned or constant in valid range
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exists(BinaryShiftOperation shift, Expr right |
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shift = x and
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shift = x and
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right = shift.getRightOperand() and
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not isUnsignedType(right.getExplicitlyConverted().getType()) and
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not isValidShiftConstantRange(right, shift.getLeftOperand().getExplicitlyConverted().getType()) and
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message =
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"Shift operator '" + shift.getOperator() +
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"' requires unsigned right operand or constant in valid range."
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)
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)
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select x, message

‎cpp/misra/test/rules/RULE-7-0-4/InappropriateBitwiseOrShiftOperands.expected

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| test.cpp:14:3:14:13 | ... & ... | Binary bitwise operator '&' requires both operands to be unsigned. |
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| test.cpp:15:3:15:13 | ... \| ... | Binary bitwise operator '\|' requires both operands to be unsigned. |
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| test.cpp:16:3:16:13 | ... ^ ... | Binary bitwise operator '^' requires both operands to be unsigned. |
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| test.cpp:18:3:18:13 | ... & ... | Binary bitwise operator '&' requires both operands to be unsigned. |
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| test.cpp:19:3:19:13 | ... \| ... | Binary bitwise operator '\|' requires both operands to be unsigned. |
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| test.cpp:30:3:30:15 | ... &= ... | Compound assignment bitwise operator '&=' requires both operands to be unsigned. |
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| test.cpp:31:3:31:15 | ... \|= ... | Compound assignment bitwise operator '\|=' requires both operands to be unsigned. |
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| test.cpp:32:3:32:15 | ... ^= ... | Compound assignment bitwise operator '^=' requires both operands to be unsigned. |
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| test.cpp:42:3:42:6 | ~ ... | Bit complement operator '~' requires unsigned operand. |
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| test.cpp:54:3:54:9 | ... << ... | Shift operator '<<' requires unsigned left operand. |
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| test.cpp:55:3:55:11 | ... << ... | Shift operator '<<' requires unsigned left operand. |
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| test.cpp:63:3:63:18 | ... << ... | Shift operator '<<' requires unsigned left operand. |
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| test.cpp:74:3:74:11 | ... << ... | Shift operator '<<' requires unsigned right operand or constant in valid range. |
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| test.cpp:75:3:75:11 | ... >> ... | Shift operator '>>' requires unsigned right operand or constant in valid range. |
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| test.cpp:85:3:85:11 | ... << ... | Shift operator '<<' requires unsigned right operand or constant in valid range. |
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| test.cpp:86:3:86:11 | ... << ... | Shift operator '<<' requires unsigned right operand or constant in valid range. |
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| test.cpp:87:3:87:11 | ... >> ... | Shift operator '>>' requires unsigned right operand or constant in valid range. |
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| test.cpp:97:3:97:9 | ... << ... | Shift operator '<<' requires unsigned left operand. |
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| test.cpp:98:3:98:9 | ... << ... | Shift operator '<<' requires unsigned left operand. |
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| test.cpp:99:3:99:9 | ... << ... | Shift operator '<<' requires unsigned left operand. |
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| test.cpp:100:3:100:9 | ... << ... | Shift operator '<<' requires unsigned left operand. |
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| test.cpp:104:3:104:11 | ... << ... | Shift operator '<<' requires unsigned left operand. |
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| test.cpp:106:3:106:17 | ... << ... | Shift operator '<<' requires unsigned left operand. |
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| test.cpp:112:3:112:10 | ... << ... | Shift operator '<<' requires unsigned left operand. |
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| test.cpp:120:3:120:11 | ... >> ... | Shift operator '>>' requires unsigned left operand. |

‎cpp/misra/test/rules/RULE-7-0-4/InappropriateBitwiseOrShiftOperands.qlref

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rules/RULE-7-0-4/InappropriateBitwiseOrShiftOperands.ql

‎cpp/misra/test/rules/RULE-7-0-4/test.cpp

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#include <climits>
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#include <cstdint>
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void test_binary_bitwise_operators_unsigned_operands() {
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std::uint32_t u32a = 0x12345678U;
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std::uint32_t u32b = 0x87654321U;
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std::int32_t s32a = 0x12345678;
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std::int32_t s32b = 0x87654321;
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u32a & u32b; // COMPLIANT
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u32a | u32b; // COMPLIANT
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u32a ^ u32b; // COMPLIANT
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s32a & s32b; // NON_COMPLIANT
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s32a | s32b; // NON_COMPLIANT
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s32a ^ s32b; // NON_COMPLIANT
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s32a & u32b; // NON_COMPLIANT
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u32a | s32b; // NON_COMPLIANT
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}
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void test_compound_assignment_bitwise_operators() {
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std::uint32_t u32 = 0x12345678U;
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std::int32_t s32 = 0x12345678;
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u32 &= 0xFFFFU; // COMPLIANT
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u32 |= 0x1000U; // COMPLIANT
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u32 ^= 0x5555U; // COMPLIANT
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s32 &= 0xFFFF; // NON_COMPLIANT
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s32 |= 0x1000; // NON_COMPLIANT
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s32 ^= 0x5555; // NON_COMPLIANT
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}
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void test_bit_complement_operator() {
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std::uint32_t u32 = 0x12345678U;
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std::uint8_t u8 = 0x55U;
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std::int32_t s32 = 0x12345678;
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~u32; // COMPLIANT
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~u8; // COMPLIANT
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~s32; // NON_COMPLIANT
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}
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void test_shift_operators_left_operand_type() {
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std::uint32_t u32 = 0x12345678U;
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std::uint8_t u8 = 2U;
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std::int32_t s32 = 0x12345678;
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1U << u8; // COMPLIANT
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1U << 31; // COMPLIANT
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u32 << 2U; // COMPLIANT
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1 << u8; // NON_COMPLIANT
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s32 << 2U; // NON_COMPLIANT
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}
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void test_shift_operators_with_promotion() {
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std::uint8_t u8 = 1U;
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std::uint16_t u16 = 2U;
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static_cast<std::uint16_t>(u8 + u16) << 2U; // COMPLIANT
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(u8 + u16) << 2U; // NON_COMPLIANT
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}
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void test_shift_operators_right_operand_unsigned() {
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std::uint32_t u32 = 0x12345678U;
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std::uint8_t u8 = 2U;
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std::int8_t s8 = 2;
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u32 << u8; // COMPLIANT
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u32 >> u8; // COMPLIANT
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u32 << s8; // NON_COMPLIANT
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u32 >> s8; // NON_COMPLIANT
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}
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void test_shift_operators_right_operand_constant_range() {
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std::uint32_t u32 = 0x12345678U;
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u32 << 0; // COMPLIANT
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u32 << 31; // COMPLIANT
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u32 >> 15; // COMPLIANT
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u32 << 32; // NON_COMPLIANT
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u32 << 64; // NON_COMPLIANT
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u32 >> 32; // NON_COMPLIANT
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}
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void test_exception_signed_constant_left_operand() {
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// Exception cases for signed constant expressions
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1 << 30; // COMPLIANT
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2 << 29; // COMPLIANT
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4 << 28; // COMPLIANT
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8 << 27; // COMPLIANT
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1 << 31; // NON_COMPLIANT
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2 << 30; // NON_COMPLIANT
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4 << 29; // NON_COMPLIANT
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8 << 28; // NON_COMPLIANT
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1LL << 31; // COMPLIANT - 64 bit type
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1LL << 62; // COMPLIANT - 64 bit type
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1LL << 63; // NON_COMPLIANT - 64 bit type
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0x40000000 << 1; // NON_COMPLIANT
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}
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void test_exception_non_constant_signed_operand() {
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std::int32_t s32 = 1;
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s32 << 2; // NON_COMPLIANT
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}
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void test_right_shift_signed_operands() {
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std::uint32_t u32 = 0x80000000U;
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std::int32_t s32 = -1;
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u32 >> 1U; // COMPLIANT
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s32 >> 1U; // NON_COMPLIANT
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}

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