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RULE-7-0-1 - NoConversionFromBool
Detects implicit and explicit conversions from type bool to other types, preventing potential confusion between bitwise and logical operators and ensuring clear type usage. [a]
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‎cpp/misra/src/rules/RULE-7-0-1/NoConversionFromBool.ql‎

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/**
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* @id cpp/misra/no-conversion-from-bool
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* @name RULE-7-0-1: There shall be no conversion from type bool
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* @description Converting a bool type (implicitly or explicitly) to another type can lead to
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* unintended behavior and code obfuscation, particularly when using bitwise operators
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* instead of logical operators.
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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-7-0-1
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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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from Expr e, Conversion conv
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where
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not isExcluded(e, ConversionsPackage::noConversionFromBoolQuery()) and
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conv = e.getConversion() and
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conv.getExpr().getType().stripTopLevelSpecifiers() instanceof BoolType and
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not conv.getType().stripTopLevelSpecifiers() instanceof BoolType and
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// Exclude cases that are explicitly allowed
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not (
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// Exception: equality operators with both bool operands
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exists(EQExpr eq |
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eq.getAnOperand() = e and
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eq.getLeftOperand().getType().stripTopLevelSpecifiers() instanceof BoolType and
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eq.getRightOperand().getType().stripTopLevelSpecifiers() instanceof BoolType
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) or
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exists(NEExpr ne |
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ne.getAnOperand() = e and
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ne.getLeftOperand().getType().stripTopLevelSpecifiers() instanceof BoolType and
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ne.getRightOperand().getType().stripTopLevelSpecifiers() instanceof BoolType
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) or
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// Exception: explicit constructor calls
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exists(ConstructorCall cc | cc.getAnArgument() = e) or
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// Exception: assignment to bit-field of length 1
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exists(AssignExpr assign |
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assign.getRValue() = e and
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assign.getLValue().(ValueFieldAccess).getTarget() instanceof BitField and
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assign.getLValue().(ValueFieldAccess).getTarget().(BitField).getNumBits() = 1
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)
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)
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select e, "Conversion from 'bool' to '" + conv.getType().toString() + "'."

‎cpp/misra/test/rules/RULE-7-0-1/NoConversionFromBool.expected‎

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| test.cpp:23:9:23:10 | b1 | Conversion from 'bool' to 'int'. |
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| test.cpp:23:14:23:15 | b2 | Conversion from 'bool' to 'int'. |
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| test.cpp:24:9:24:10 | b1 | Conversion from 'bool' to 'int'. |
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| test.cpp:24:14:24:15 | b2 | Conversion from 'bool' to 'int'. |
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| test.cpp:25:9:25:10 | b1 | Conversion from 'bool' to 'int'. |
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| test.cpp:25:14:25:15 | b2 | Conversion from 'bool' to 'int'. |
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| test.cpp:26:10:26:11 | b1 | Conversion from 'bool' to 'int'. |
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| test.cpp:29:9:29:10 | b1 | Conversion from 'bool' to 'int'. |
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| test.cpp:29:14:29:15 | b2 | Conversion from 'bool' to 'int'. |
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| test.cpp:30:9:30:10 | b1 | Conversion from 'bool' to 'int'. |
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| test.cpp:30:14:30:15 | b2 | Conversion from 'bool' to 'int'. |
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| test.cpp:31:9:31:10 | b1 | Conversion from 'bool' to 'int'. |
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| test.cpp:31:15:31:16 | b2 | Conversion from 'bool' to 'int'. |
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| test.cpp:32:9:32:10 | b1 | Conversion from 'bool' to 'int'. |
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| test.cpp:32:15:32:16 | b2 | Conversion from 'bool' to 'int'. |
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| test.cpp:35:9:35:10 | b1 | Conversion from 'bool' to 'int'. |
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| test.cpp:36:9:36:10 | b1 | Conversion from 'bool' to 'int'. |
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| test.cpp:37:9:37:10 | b1 | Conversion from 'bool' to 'int'. |
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| test.cpp:40:22:40:23 | b1 | Conversion from 'bool' to 'double'. |
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| test.cpp:41:22:41:23 | b1 | Conversion from 'bool' to 'double'. |
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| test.cpp:42:30:42:31 | b1 | Conversion from 'bool' to 'int'. |
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| test.cpp:45:36:45:37 | b1 | Conversion from 'bool' to 'int8_t'. |
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| test.cpp:46:38:46:39 | b1 | Conversion from 'bool' to 'int32_t'. |
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| test.cpp:49:8:49:9 | b1 | Conversion from 'bool' to 'int32_t'. |
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| test.cpp:50:8:50:9 | b1 | Conversion from 'bool' to 'double'. |
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| test.cpp:53:13:53:14 | b1 | Conversion from 'bool' to 'int'. |
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| test.cpp:59:11:59:12 | b1 | Conversion from 'bool' to 'int8_t'. |
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| test.cpp:60:12:60:13 | b1 | Conversion from 'bool' to 'int32_t'. |
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| test.cpp:61:10:61:11 | b1 | Conversion from 'bool' to 'double'. |

‎cpp/misra/test/rules/RULE-7-0-1/NoConversionFromBool.qlref‎

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rules/RULE-7-0-1/NoConversionFromBool.ql

‎cpp/misra/test/rules/RULE-7-0-1/test.cpp‎

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#include <cstdint>
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struct A {
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explicit A(bool) {}
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};
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struct BitField {
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std::uint8_t bit : 1;
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};
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void f1(std::int32_t n) {}
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void f2(double d) {}
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void test_bool_conversion_violations() {
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bool b1 = true;
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bool b2 = false;
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double d1 = 1.0;
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std::int8_t s8a = 0;
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std::int32_t s32a = 0;
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BitField bf;
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// Bitwise operations - non-compliant
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if (b1 & b2) {} // NON_COMPLIANT
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if (b1 | b2) {} // NON_COMPLIANT
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if (b1 ^ b2) {} // NON_COMPLIANT
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if (~b1) {} // NON_COMPLIANT
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// Relational operations - non-compliant
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if (b1 < b2) {} // NON_COMPLIANT
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if (b1 > b2) {} // NON_COMPLIANT
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if (b1 <= b2) {} // NON_COMPLIANT
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if (b1 >= b2) {} // NON_COMPLIANT
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// Comparison with integer literals - non-compliant
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if (b1 == 0) {} // NON_COMPLIANT
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if (b1 == 1) {} // NON_COMPLIANT
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if (b1 != 0) {} // NON_COMPLIANT
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// Arithmetic operations - non-compliant
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double l1 = d1 * b1; // NON_COMPLIANT
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double l2 = d1 + b1; // NON_COMPLIANT
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std::int32_t l3 = s32a + b1; // NON_COMPLIANT
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// Explicit casts to integral types - non-compliant
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s8a = static_cast<std::int8_t>(b1); // NON_COMPLIANT
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s32a = static_cast<std::int32_t>(b1); // NON_COMPLIANT
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// Function parameter conversion - non-compliant
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f1(b1); // NON_COMPLIANT
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f2(b1); // NON_COMPLIANT
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// Switch statement - non-compliant
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switch (b1) { // NON_COMPLIANT
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case 0: break;
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case 1: break;
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}
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// Assignment to integral types - non-compliant
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s8a = b1; // NON_COMPLIANT
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s32a = b1; // NON_COMPLIANT
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d1 = b1; // NON_COMPLIANT
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}
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void test_bool_conversion_compliant() {
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bool b1 = true;
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bool b2 = false;
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std::int8_t s8a = 0;
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BitField bf;
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// Boolean equality operations - compliant
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if (b1 == false) {} // COMPLIANT
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if (b1 == true) {} // COMPLIANT
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if (b1 == b2) {} // COMPLIANT
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if (b1 != b2) {} // COMPLIANT
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// Logical operations - compliant
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if (b1 && b2) {} // COMPLIANT
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if (b1 || b2) {} // COMPLIANT
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if (!b1) {} // COMPLIANT
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// Conditional operator without conversion - compliant
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s8a = b1 ? 3 : 7; // COMPLIANT
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// Function parameter without conversion - compliant
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f1(b1 ? 1 : 0); // COMPLIANT
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// Explicit constructor calls - compliant
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A l1{true}; // COMPLIANT
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A l2(false); // COMPLIANT
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A l3 = static_cast<A>(true); // COMPLIANT
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// Assignment to constructor - compliant
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A l4 = A{false}; // COMPLIANT
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// Bit-field assignment exception - compliant
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bf.bit = b1; // COMPLIANT
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}

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