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RULE-7-11-3 - FunctionPointerConversionContext
Detects inappropriate implicit conversions from function type to pointer-to-function type outside of static_cast or assignment contexts. Prevents ambiguous code where function pointer usage in boolean or arithmetic expressions may contradict developer intent. [a]
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Lines changed: 180 additions & 2 deletions

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‎cpp/misra/src/codingstandards/cpp/misra/BuiltInTypeRules.qll‎

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@@ -121,14 +121,14 @@ class CanonicalIntegerTypes extends NumericType, IntegralType {
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CanonicalIntegerTypes() { this = this.getCanonicalArithmeticType() }
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}
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predicate isAssignment(Expr source, NumericType targetType, string context) {
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predicate isAssignment(Expr source, Type targetType, string context) {
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exists(Expr preConversionAssignment |
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isPreConversionAssignment(preConversionAssignment, targetType, context) and
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preConversionAssignment.getExplicitlyConverted() = source
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)
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}
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predicate isPreConversionAssignment(Expr source, NumericType targetType, string context) {
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predicate isPreConversionAssignment(Expr source, Type targetType, string context) {
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// Assignment expression (which excludes compound assignments)
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exists(AssignExpr assign |
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assign.getRValue() = source and

‎cpp/misra/src/rules/RULE-7-11-3/FunctionPointerConversionContext.ql‎

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/**
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* @id cpp/misra/function-pointer-conversion-context
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* @name RULE-7-11-3: A conversion from function type to pointer-to-function type shall only occur in appropriate contexts
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* @description Converting a function type to a pointer-to-function type outside of static_cast or
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* assignment to a pointer-to-function object creates ambiguous behavior and potential
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* unintended effects.
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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-7-11-3
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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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import codingstandards.cpp.Type
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/**
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* An `Expr` representing an implicit conversion from a function type to a pointer-to-function type.
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*
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* Despite the name, these are not `Conversion`s in our model. Instead, they are expressions
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* representing functions that have been implicilty converted to function pointers.
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*/
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abstract class FunctionToFunctionPointerConversion extends Expr { }
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/**
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* A `FunctionAccess` that has been implicitly converted to a function pointer type.
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*/
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class FunctionAccessConversionToFunctionPointer extends FunctionAccess,
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FunctionToFunctionPointerConversion
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{
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FunctionAccessConversionToFunctionPointer() {
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this.getType().getUnspecifiedType() instanceof FunctionPointerIshType
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}
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}
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/**
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* A `Call` to a `ConversionOperator` that converts a lambda to a function pointer type.
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*/
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class LambdaFunctionPointerConversion extends Call, FunctionToFunctionPointerConversion {
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LambdaFunctionPointerConversion() {
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this.getTarget().(ConversionOperator).getDestType() instanceof FunctionPointerIshType and
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this.getQualifier().getType().getUnspecifiedType() instanceof Closure
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}
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}
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from FunctionToFunctionPointerConversion f
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where
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not isExcluded(f, ConversionsPackage::functionPointerConversionContextQuery()) and
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// Not converted by an explicit static cast
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not exists(Conversion c |
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c.getExpr() = f and
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not c.isImplicit() and
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c.getType().getUnspecifiedType() instanceof FunctionPointerIshType
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) and
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// Not a MISRA compliant assignment to a function pointer type
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not exists(FunctionPointerIshType targetType | isAssignment(f, targetType, _))
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select f,
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"Inappropriate conversion from function type to pointer-to-function type in '" + f.toString() +
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"'."

‎cpp/misra/test/rules/RULE-7-11-3/FunctionPointerConversionContext.expected‎

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| test.cpp:11:7:11:7 | f | Inappropriate conversion from function type to pointer-to-function type in 'f'. |
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| test.cpp:14:7:14:7 | f | Inappropriate conversion from function type to pointer-to-function type in 'f'. |
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| test.cpp:18:16:18:16 | f | Inappropriate conversion from function type to pointer-to-function type in 'f'. |
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| test.cpp:21:14:21:14 | f | Inappropriate conversion from function type to pointer-to-function type in 'f'. |
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| test.cpp:25:7:25:7 | call to operator void (*)() | Inappropriate conversion from function type to pointer-to-function type in 'call to operator void (*)()'. |
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| test.cpp:33:14:33:14 | call to operator void (*)() | Inappropriate conversion from function type to pointer-to-function type in 'call to operator void (*)()'. |
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| test.cpp:61:13:61:13 | f | Inappropriate conversion from function type to pointer-to-function type in 'f'. |
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| test.cpp:64:13:64:13 | f | Inappropriate conversion from function type to pointer-to-function type in 'f'. |
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| test.cpp:67:7:67:7 | f | Inappropriate conversion from function type to pointer-to-function type in 'f'. |
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| test.cpp:71:7:71:7 | f | Inappropriate conversion from function type to pointer-to-function type in 'f'. |
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| test.cpp:74:7:74:7 | f | Inappropriate conversion from function type to pointer-to-function type in 'f'. |
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| test.cpp:77:7:77:7 | f | Inappropriate conversion from function type to pointer-to-function type in 'f'. |
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| test.cpp:83:7:83:7 | f | Inappropriate conversion from function type to pointer-to-function type in 'f'. |
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| test.cpp:87:7:87:7 | f | Inappropriate conversion from function type to pointer-to-function type in 'f'. |
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| test.cpp:92:7:92:7 | call to operator void (*)() | Inappropriate conversion from function type to pointer-to-function type in 'call to operator void (*)()'. |
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| test.cpp:96:7:96:7 | call to operator void (*)() | Inappropriate conversion from function type to pointer-to-function type in 'call to operator void (*)()'. |

‎cpp/misra/test/rules/RULE-7-11-3/FunctionPointerConversionContext.qlref‎

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rules/RULE-7-11-3/FunctionPointerConversionContext.ql

‎cpp/misra/test/rules/RULE-7-11-3/test.cpp‎

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#include <cstdint>
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#include <iostream>
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// Test functions
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extern int *f();
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void f1(double);
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void f1(std::uint32_t);
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void simple_function();
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void test_function_to_pointer_conversion() {
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if (f) { // NON_COMPLIANT
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}
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if (f == nullptr) { // NON_COMPLIANT
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}
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std::cout << std::boolalpha // COMPLIANT - considered assignment
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<< f; // NON_COMPLIANT - not assignment
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// Non-compliant: Unary plus operator causing pointer decay
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auto l1 = +f; // NON_COMPLIANT
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auto lam = []() {};
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// Lambda used in boolean context
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if (lam) { // NON_COMPLIANT
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}
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// Lambda used in address-of operator
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if (&lam) { // COMPLIANT
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}
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// Unary plus on lambda
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auto l2 = +lam; // NON_COMPLIANT
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// Using address-of operator
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if (&f != nullptr) { // COMPLIANT
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}
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// Function call
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(f)(); // COMPLIANT
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lam(); // COMPLIANT
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// static_cast conversion
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auto selected = static_cast<void (*)(std::uint32_t)>(f1); // COMPLIANT
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// Assignment to pointer-to-function type
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void (*p)() = lam; // COMPLIANT
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// Assignment to pointer-to-function type
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int *(*func_ptr)() = f; // COMPLIANT
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// Using address-of operator
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void (*simple_ptr)() = &simple_function; // COMPLIANT
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// Direct assignment without conversion
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void (*simple_ptr2)() = simple_function; // COMPLIANT
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}
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void test_arithmetic_expressions() {
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// Function used in arithmetic expression (triggers pointer decay)
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auto l3 = f + 0; // NON_COMPLIANT
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// Function used in arithmetic subtraction expression
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auto l4 = f - 0; // NON_COMPLIANT
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// Function used in comparison with non-null pointer
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if (f > nullptr) { // NON_COMPLIANT
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}
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// Function used in relational operators
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if (f < nullptr) { // NON_COMPLIANT
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}
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if (f <= nullptr) { // NON_COMPLIANT
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}
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if (f >= nullptr) { // NON_COMPLIANT
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}
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}
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void test_logical_expressions() {
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// Function used in logical AND expression
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if (f && true) { // NON_COMPLIANT
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}
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// Function used in logical OR expression
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if (f || false) { // NON_COMPLIANT
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}
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// Lambda used in logical AND expression
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auto lam = []() {};
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if (lam && true) { // NON_COMPLIANT
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}
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// Lambda used in logical OR expression
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if (lam || false) { // NON_COMPLIANT
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}
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}

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