C++: Address review comments

Author: jketema

cpp/ql/lib/semmle/code/cpp/Enum.qll

@@ -55,6 +55,12 @@ class Enum extends UserType, IntegralOrEnumType {
     not exists(UserType.super.getSize()) and result = 4
   }
 
+  override int getBitWidth() {
+    result = UserType.super.getBitWidth()
+    or
+    not exists(UserType.super.getBitWidth()) and result = 32
+  }
+
   /** See `Type.isDeeplyConst` and `Type.isDeeplyConstBelow`. Internal. */
   override predicate isDeeplyConstBelow() { any() } // No subparts
 

cpp/ql/lib/semmle/code/cpp/Type.qll

@@ -1189,6 +1189,8 @@ class Decltype extends Type, NameQualifyingElement {
 
   override int getSize() { result = this.getBaseType().getSize() }
 
+  override int getBitWidth() { result = this.getBaseType().getBitWidth() }
+
   override int getAlignment() { result = this.getBaseType().getAlignment() }
 
   override int getPointerIndirectionLevel() {
@@ -1249,6 +1251,8 @@ class TypeofType extends Type {
 
   override int getSize() { result = this.getBaseType().getSize() }
 
+  override int getBitWidth() { result = this.getBaseType().getBitWidth() }
+
   override int getAlignment() { result = this.getBaseType().getAlignment() }
 
   override int getPointerIndirectionLevel() {
@@ -1394,6 +1398,8 @@ class IntrinsicTransformedType extends Type {
 
   override int getSize() { result = this.getBaseType().getSize() }
 
+  override int getBitWidth() { result = this.getBaseType().getBitWidth() }
+
   override int getAlignment() { result = this.getBaseType().getAlignment() }
 
   override int getPointerIndirectionLevel() {
@@ -1519,6 +1525,8 @@ class SpecifiedType extends DerivedType {
 
   override int getSize() { result = this.getBaseType().getSize() }
 
+  override int getBitWidth() { result = this.getBaseType().getBitWidth() }
+
   override int getAlignment() { result = this.getBaseType().getAlignment() }
 
   override int getPointerIndirectionLevel() {
@@ -1594,6 +1602,8 @@ class ArrayType extends DerivedType {
    */
   override int getSize() { result = this.getByteSize() }
 
+  override int getBitWidth() { result = this.getByteSize() * 8 }
+
   override string explain() {
     if exists(this.getArraySize())
     then

cpp/ql/lib/semmle/code/cpp/TypedefType.qll

@@ -26,6 +26,8 @@ class TypedefType extends UserType {
 
   override int getSize() { result = this.getBaseType().getSize() }
 
+  override int getBitWidth() { result = this.getBaseType().getBitWidth() }
+
   override int getAlignment() { result = this.getBaseType().getAlignment() }
 
   override int getPointerIndirectionLevel() {

cpp/ql/src/Likely Bugs/Conversion/ImplicitDowncastFromBitfield.ql

@@ -21,7 +21,7 @@ where
     else fct = va.getFullyConverted().getType()
   ) and
   fi.getNumBits() > fct.getBitWidth() and
-  va.getExplicitlyConverted().getType().getSize() > fct.getSize() and
+  va.getExplicitlyConverted().getType().getBitWidth() > fct.getBitWidth() and
   va.getTarget() = fi and
   not fct.getUnspecifiedType() instanceof BoolType
 select va, "Implicit downcast of bitfield $@.", fi, fi.toString()