Rule 7.0.6: Handle explicit conversions

Consider the conversion as the source, not the pre-conversion
value.

Author: lcartey

cpp/misra/src/codingstandards/cpp/misra/StandardConversions.qll

@@ -117,6 +117,13 @@ class CanonicalIntegerTypes extends NumericType, IntegralType {
 }
 
 predicate isAssignment(Expr source, NumericType targetType, string context) {
+  exists(Expr preConversionAssignment |
+    isPreConversionAssignment(preConversionAssignment, targetType, context) and
+    preConversionAssignment.getExplicitlyConverted() = source
+  )
+}
+
+predicate isPreConversionAssignment(Expr source, NumericType targetType, string context) {
   // Assignment expression (which excludes compound assignments)
   exists(AssignExpr assign |
     assign.getRValue() = source and
@@ -261,4 +268,6 @@ CanonicalIntegerTypes getBitFieldType(BitField bf) {
 /**
  * Holds if the `source` expression is assigned to a bit field.
  */
-predicate isAssignedToBitfield(Expr source, BitField bf) { source = bf.getAnAssignedValue() }
+predicate isAssignedToBitfield(Expr source, BitField bf) {
+  source = bf.getAnAssignedValue().getExplicitlyConverted()
+}

cpp/misra/src/rules/RULE-7-0-6/NumericAssignmentTypeMismatch.ql

@@ -101,7 +101,7 @@ predicate isValidWidening(Expr source, NumericType sourceType, NumericType targe
   // Same type category and signedness, source size smaller, source is id-expression or has constructor exception
   (
     source instanceof IdExpression or
-    hasConstructorException(any(Call call | call.getAnArgument() = source))
+    hasConstructorException(any(Call call | call.getAnArgument().getExplicitlyConverted() = source))
   ) and
   sourceType.getTypeCategory() = targetType.getTypeCategory() and
   sourceType.getSignedness() = targetType.getSignedness() and
@@ -163,7 +163,7 @@ predicate isOverloadIndependent(Call call, Expr arg) {
  */
 predicate shouldHaveSameType(Expr source) {
   exists(Call call |
-    call.getAnArgument() = source and
+    call.getAnArgument().getExplicitlyConverted() = source and
     isAssignment(source, _, _) and
     not hasConstructorException(call)
   |
@@ -172,7 +172,7 @@ predicate shouldHaveSameType(Expr source) {
     // Passed as a varargs parameter
     exists(int i |
       call.getTarget().isVarargs() and
-      call.getArgument(i) = source and
+      call.getArgument(i).getExplicitlyConverted() = source and
       // Argument is greater than the number of parameters
       call.getTarget().getNumberOfParameters() <= i
     )

cpp/misra/test/rules/RULE-7-0-6/NumericAssignmentTypeMismatch.expected

@@ -11,8 +11,8 @@
 | test.cpp:97:13:97:14 | m1 | Assignment between incompatible numeric types from 'uint8_t' to 'uint32_t'. |
 | test.cpp:98:13:98:14 | m2 | Assignment between incompatible numeric types from 'uint16_t' to 'uint64_t'. |
 | test.cpp:103:9:103:14 | ... + ... | Assignment between incompatible numeric types from 'int' to 'uint32_t'. |
-| test.cpp:104:10:104:11 | u8 | Assignment between incompatible numeric types from 'uint8_t' to 'uint32_t'. |
-| test.cpp:105:35:105:36 | u8 | Assignment between incompatible numeric types from 'uint8_t' to 'uint32_t'. |
+| test.cpp:104:9:104:12 | (...) | Assignment between incompatible numeric types from 'uint8_t' to 'uint32_t'. |
+| test.cpp:105:9:105:37 | static_cast<uint8_t>... | Assignment between incompatible numeric types from 'uint8_t' to 'uint32_t'. |
 | test.cpp:110:8:110:14 | ... + ... | Assignment between incompatible numeric types from 'int' to 'uint8_t'. |
 | test.cpp:111:21:111:27 | ... + ... | Assignment between incompatible numeric types from 'int' to 'int16_t'. |
 | test.cpp:134:11:134:11 | 4 | Assignment between incompatible numeric types from 'int' to 'unsigned char'. |
@@ -84,6 +84,7 @@
 | test.cpp:553:12:553:13 | l1 | Assignment between incompatible numeric types from 'uint8_t' to 'int32_t'. |
 | test.cpp:554:12:554:13 | l1 | Assignment between incompatible numeric types from 'uint8_t' to 'float'. |
 | test.cpp:555:12:555:13 | l1 | Assignment between incompatible numeric types from 'uint8_t' to 'double'. |
+| test.cpp:585:9:585:37 | static_cast<int16_t>... | Assignment between incompatible numeric types from 'int16_t' to 'int32_t'. |
 | test_aggregate.cpp:29:22:29:24 | u16 | Assignment between incompatible numeric types from 'uint16_t' to 'uint8_t'. |
 | test_aggregate.cpp:31:26:31:28 | u32 | Assignment between incompatible numeric types from 'uint32_t' to 'uint16_t'. |
 | test_aggregate.cpp:33:31:33:33 | u32 | Assignment between incompatible numeric types from 'uint32_t' to 'int32_t'. |
@@ -315,7 +316,7 @@
 | test_specified.cpp:342:8:342:14 | ... + ... | Assignment between incompatible numeric types from 'int' to 'uint8_t'. |
 | test_specified.cpp:343:8:343:14 | ... + ... | Assignment between incompatible numeric types from 'int' to 'uint8_t'. |
 | test_specified.cpp:344:8:344:14 | ... + ... | Assignment between incompatible numeric types from 'int' to 'uint8_t'. |
-| test_specified.cpp:351:10:351:11 | l2 | Assignment between incompatible numeric types from 'uint8_t' to 'uint32_t'. |
-| test_specified.cpp:352:10:352:11 | l3 | Assignment between incompatible numeric types from 'uint8_t' to 'uint32_t'. |
+| test_specified.cpp:351:9:351:12 | (...) | Assignment between incompatible numeric types from 'uint8_t' to 'uint32_t'. |
+| test_specified.cpp:352:9:352:12 | (...) | Assignment between incompatible numeric types from 'uint8_t' to 'uint32_t'. |
 | test_specified.cpp:370:18:370:20 | 300 | Assignment between incompatible numeric types from 'int' to 'const uint8_t'. |
 | test_specified.cpp:370:23:370:27 | 70000 | Assignment between incompatible numeric types from 'int' to 'volatile uint16_t'. |

cpp/misra/test/rules/RULE-7-0-6/test.cpp

@@ -566,4 +566,56 @@ void test_constructor_field_initializers() {
   ConstructorTest l6;              // Test third constructor
   ConstructorTest l7(0);           // Test fourth constructor
   ConstructorTest l8(l1, l1, l3);  // Test fifth constructor
+}
+
+// Test explicit casts
+void test_explicit_casts() {
+  std::uint8_t l1 = 42;
+  std::uint16_t l2 = 1000;
+  std::int8_t l3 = -10;
+  std::int32_t l4 = -100;
+  float l5 = 3.14f;
+  double l6 = 2.718;
+
+  // Explicit cast expressions are treated as expressions, not id-expressions
+  u8 = static_cast<std::uint8_t>(l2);   // COMPLIANT
+  u16 = static_cast<std::uint16_t>(l1); // COMPLIANT
+  s8 = static_cast<std::int8_t>(l4);    // COMPLIANT
+  s32 = static_cast<std::int32_t>(l3);  // COMPLIANT
+  s32 = static_cast<std::int16_t>(l3);  // NON_COMPLIANT
+
+  // Type category conversions with explicit casts
+  f = static_cast<float>(l4);          // COMPLIANT
+  s32 = static_cast<std::int32_t>(l5); // COMPLIANT
+
+  // Size conversions with explicit casts
+  d = static_cast<double>(l5); // COMPLIANT
+  l5 = static_cast<float>(l6); // COMPLIANT
+
+  // C-style casts (also expressions)
+  u8 = (std::uint8_t)l2; // COMPLIANT
+  s8 = (std::int8_t)l4;  // COMPLIANT
+  f = (float)l4;         // COMPLIANT
+
+  // Functional style casts (also expressions)
+  u8 = std::uint8_t(l2); // COMPLIANT
+  s8 = std::int8_t(l4);  // COMPLIANT
+  f = float(l4);         // COMPLIANT
+
+  // Const_cast (creates expressions)
+  const std::uint8_t l7 = 100;
+  u8 = const_cast<std::uint8_t &>(l7); // COMPLIANT
+
+  // Reinterpret_cast (creates expressions)
+  u32 = reinterpret_cast<std::uint32_t &>(l4); // COMPLIANT
+
+  // Assignment to variables through explicit casts
+  std::uint32_t l8;
+  std::uint16_t l9;
+  l8 = static_cast<std::uint32_t>(l9); // COMPLIANT
+  l9 = static_cast<std::uint16_t>(l8); // COMPLIANT
+
+  // Function calls with explicit casts
+  f1(static_cast<std::int64_t>(l4)); // COMPLIANT
+  f2(static_cast<std::int32_t>(l4)); // COMPLIANT
 }