C++: Don't unresolve 'this'

For example, if you have 3 types called T, where t1 and t2 are defined
but t3 isn't, then you will have

    unspecifiedtype(t1, t1)
    unspecifiedtype(t2, t2)
    unspecifiedtype(t3, t3)

    t1 = resolve(t1)
    t1 = resolve(t3)
    t2 = resolve(t2)
    t2 = resolve(t3)

so given

    Type getUnspecifiedType() {
        unspecifiedtype(unresolve(this), unresolve(result))
    }

you get t1.getUnspecifiedType() = t2.

I think that in general the best thing to do is to not unresolve 'this',
but to just take the underlying value.

Author: ian-semmle

cpp/ql/src/semmle/code/cpp/AutogeneratedFile.qll

@@ -35,7 +35,7 @@ class AutogeneratedFile extends File {
   cached AutogeneratedFile() {
     exists(int limit, int head |
       head <= 5 and
-      limit = max(int line | locations_default(_, unresolveElement(this), head, _, line, _)) + 5
+      limit = max(int line | locations_default(_, underlyingElement(this), head, _, line, _)) + 5
     |
       exists (Comment c | c.getFile() = this and c.getLocation().getStartLine() <= limit and isAutogeneratedComment(c))
     )

cpp/ql/src/semmle/code/cpp/Class.qll

@@ -12,7 +12,7 @@ private import semmle.code.cpp.internal.Type
  */
 class Class extends UserType {
   Class() {
-    isClass(unresolveElement(this))
+    isClass(underlyingElement(this))
   }
 
   /** Gets a child declaration of this class. */
@@ -75,7 +75,7 @@ class Class extends UserType {
    * If you also want template instantiations of results, see
    * `getAMember(int)`.
    */
-  Declaration getCanonicalMember(int index) { member(unresolveElement(this),index,unresolveElement(result)) }
+  Declaration getCanonicalMember(int index) { member(underlyingElement(this),index,unresolveElement(result)) }
 
   /**
    * Gets the (zero-based) `index`th canonical member declared in this
@@ -94,7 +94,7 @@ class Class extends UserType {
    * DEPRECATED: Use `getCanonicalMember(int)` or `getAMember(int)` instead.
    * Gets the `index`th member of this class.
    */
-  deprecated Declaration getMember(int index) { member(unresolveElement(this),index,unresolveElement(result)) }
+  deprecated Declaration getMember(int index) { member(underlyingElement(this),index,unresolveElement(result)) }
 
   /**
    * DEPRECATED: As this includes a somewhat arbitrary number of
@@ -416,7 +416,7 @@ class Class extends UserType {
    * compiled for. For this reason, the `is_pod_class` predicate is
    * generated by the extractor.
    */
-  predicate isPOD() { is_pod_class(unresolveElement(this)) }
+  predicate isPOD() { is_pod_class(underlyingElement(this)) }
 
   /**
    * Holds if this class is abstract, in other words whether it declares one
@@ -513,7 +513,7 @@ class Class extends UserType {
    * classes.
    */
   int getVirtualBaseClassByteOffset(Class base) {
-    virtual_base_offsets(unresolveElement(this), unresolveElement(base), result)
+    virtual_base_offsets(underlyingElement(this), unresolveElement(base), result)
   }
 
   /**
@@ -566,15 +566,15 @@ class Class extends UserType {
    * The alignment of this type in bytes (on the machine where facts were
    * extracted).
    */
-  int getAlignment() { usertypesize(unresolveElement(this),_,result) }
+  int getAlignment() { usertypesize(underlyingElement(this),_,result) }
 
   /**
    * Holds if this class is constructed from another class as a result of
    * template instantiation. It originates either from a class template or
    * from a class nested in a class template.
    */
   predicate isConstructedFrom(Class c) {
-    class_instantiation(unresolveElement(this), unresolveElement(c))
+    class_instantiation(underlyingElement(this), unresolveElement(c))
   }
 
   /**
@@ -597,7 +597,7 @@ class Class extends UserType {
    * `i`th template parameter.
    */
   Type getTemplateArgument(int i) {
-    class_template_argument(unresolveElement(this),i,unresolveElement(result))
+    class_template_argument(underlyingElement(this),i,unresolveElement(result))
   }
 
   /**
@@ -614,7 +614,7 @@ class Class extends UserType {
 
   /** Holds if this class was declared 'final'. */
   predicate isFinal() {
-    usertype_final(unresolveElement(this))
+    usertype_final(underlyingElement(this))
   }
 
   /** Gets a link target which references this class. */
@@ -631,7 +631,7 @@ class Class extends UserType {
    * using lowercase letters (e.g. "01234567-89ab-cdef-0123-456789abcdef").
    */
   string getUuid() {
-    usertype_uuid(unresolveElement(this), result)
+    usertype_uuid(underlyingElement(this), result)
   }
 
   private Type getAFieldSubobjectType() {
@@ -764,7 +764,7 @@ class ClassDerivation extends Locatable, @derivation {
    * struct D : T {};
    */
   Type getBaseType() {
-    derivations(unresolveElement(this),_,_,unresolveElement(result),_)
+    derivations(underlyingElement(this),_,_,unresolveElement(result),_)
   }
 
   /**
@@ -775,7 +775,7 @@ class ClassDerivation extends Locatable, @derivation {
    * struct D : B {};
    */
   Class getDerivedClass() {
-    derivations(unresolveElement(this),unresolveElement(result),_,_,_)
+    derivations(underlyingElement(this),unresolveElement(result),_,_,_)
   }
 
   /**
@@ -784,12 +784,12 @@ class ClassDerivation extends Locatable, @derivation {
    * derivation of B2 in "struct D : B1, B2 { ... };" would be 1.
    */
   int getIndex() {
-    derivations(unresolveElement(this),_,result,_,_)
+    derivations(underlyingElement(this),_,result,_,_)
   }
 
   /** Gets a specifier (for example "public") applied to the derivation. */
   Specifier getASpecifier() {
-    derspecifiers(unresolveElement(this),unresolveElement(result))
+    derspecifiers(underlyingElement(this),unresolveElement(result))
   }
 
   /** Holds if the derivation has specifier `s`. */
@@ -804,7 +804,7 @@ class ClassDerivation extends Locatable, @derivation {
 
   /** Gets the location of the derivation. */
   override Location getLocation() {
-    derivations(unresolveElement(this),_,_,_,result)
+    derivations(underlyingElement(this),_,_,_,result)
   }
 
   /**
@@ -816,7 +816,7 @@ class ClassDerivation extends Locatable, @derivation {
    * classes.
    */
   int getByteOffset() {
-    direct_base_offsets(unresolveElement(this), result)
+    direct_base_offsets(underlyingElement(this), result)
   }
 
   override string toString() {
@@ -869,7 +869,7 @@ class AbstractClass extends Class {
  * of class templates).
  */
 class TemplateClass extends Class {
-  TemplateClass() { usertypes(unresolveElement(this),_,6) }
+  TemplateClass() { usertypes(underlyingElement(this),_,6) }
   Class getAnInstantiation() {
     result.isConstructedFrom(this) and
     exists(result.getATemplateArgument())
@@ -998,7 +998,7 @@ class VirtualBaseClass extends Class {
  */
 class ProxyClass extends UserType {
   ProxyClass() {
-    usertypes(unresolveElement(this),_,9)
+    usertypes(underlyingElement(this),_,9)
   }
 
   /** Gets the location of the proxy class. */
@@ -1008,7 +1008,7 @@ class ProxyClass extends UserType {
 
   /** Gets the template parameter for which this is the proxy class. */
   TemplateParameter getTemplateParameter() {
-    is_proxy_class_for(unresolveElement(this),unresolveElement(result))
+    is_proxy_class_for(underlyingElement(this),unresolveElement(result))
   }
 }
 

cpp/ql/src/semmle/code/cpp/Comments.qll

@@ -6,9 +6,9 @@ import semmle.code.cpp.Element
  */
 class Comment extends Locatable, @comment {
   override string toString() { result = this.getContents() }
-  override Location getLocation() { comments(unresolveElement(this),_,result) }
-  string getContents() { comments(unresolveElement(this),result,_) }
-  Element getCommentedElement() { commentbinding(unresolveElement(this),unresolveElement(result)) }
+  override Location getLocation() { comments(underlyingElement(this),_,result) }
+  string getContents() { comments(underlyingElement(this),result,_) }
+  Element getCommentedElement() { commentbinding(underlyingElement(this),unresolveElement(result)) }
 }
 
 /**

cpp/ql/src/semmle/code/cpp/Diagnostics.qll

@@ -7,26 +7,26 @@ class Diagnostic extends Locatable, @diagnostic {
    * Gets the severity of the message, on a range from 1 to 5: 1=remark,
    * 2=warning, 3=discretionary error, 4=error, 5=catastrophic error.
    */
-  int getSeverity() { diagnostics(unresolveElement(this), result, _, _, _, _) }
+  int getSeverity() { diagnostics(underlyingElement(this), result, _, _, _, _) }
 
   /** Gets the error code for this compiler message. */
-  string getTag() { diagnostics(unresolveElement(this), _, result, _, _, _) }
+  string getTag() { diagnostics(underlyingElement(this), _, result, _, _, _) }
   predicate hasTag(string s) { this.getTag() = s }
 
   /**
    * Gets the error message text associated with this compiler
    * diagnostic.
    */
-  string getMessage() { diagnostics(unresolveElement(this), _, _, result, _, _) }
+  string getMessage() { diagnostics(underlyingElement(this), _, _, result, _, _) }
 
   /**
    * Gets the full error message text associated with this compiler
    * diagnostic.
    */
-  string getFullMessage() { diagnostics(unresolveElement(this), _, _, _, result, _) }
+  string getFullMessage() { diagnostics(underlyingElement(this), _, _, _, result, _) }
 
   /** Gets the source location corresponding to the compiler message. */
-  override Location getLocation() { diagnostics(unresolveElement(this), _, _, _, _, result) }
+  override Location getLocation() { diagnostics(underlyingElement(this), _, _, _, _, result) }
 
   override string toString() { result = this.getMessage() }
 

cpp/ql/src/semmle/code/cpp/Element.qll

@@ -16,6 +16,10 @@ cached @element unresolveElement(Element e) {
   resolveElement(result) = e
 }
 
+cached @element underlyingElement(Element e) {
+  result = e
+}
+
 /**
  * A C/C++ element. This class is the base class for all C/C++
  * elements, such as functions, classes, expressions, and so on.
@@ -136,7 +140,7 @@ class Element extends @element {
     | this = s and result = s.getParent())
 
     or
-    using_container(unresolveElement(result), unresolveElement(this))
+    using_container(unresolveElement(result), underlyingElement(this))
   }
 
   /**
@@ -158,17 +162,17 @@ class Element extends @element {
   }
 
   private Element getEnclosingElementPref() {
-    enclosingfunction(unresolveElement(this), unresolveElement(result)) or
+    enclosingfunction(underlyingElement(this), unresolveElement(result)) or
     result.(Function) = stmtEnclosingElement(this) or
     this.(LocalScopeVariable).getFunction() = result or
-    enumconstants(unresolveElement(this), unresolveElement(result), _, _, _, _) or
-    derivations(unresolveElement(this), unresolveElement(result), _, _, _) or
-    stmtparents(unresolveElement(this), _, unresolveElement(result)) or
-    exprparents(unresolveElement(this), _, unresolveElement(result)) or
-    namequalifiers(unresolveElement(this), unresolveElement(result), _, _) or
-    initialisers(unresolveElement(this), unresolveElement(result), _, _) or
-    exprconv(unresolveElement(result), unresolveElement(this)) or
-    param_decl_bind(unresolveElement(this),_,unresolveElement(result))
+    enumconstants(underlyingElement(this), unresolveElement(result), _, _, _, _) or
+    derivations(underlyingElement(this), unresolveElement(result), _, _, _) or
+    stmtparents(underlyingElement(this), _, unresolveElement(result)) or
+    exprparents(underlyingElement(this), _, unresolveElement(result)) or
+    namequalifiers(underlyingElement(this), unresolveElement(result), _, _) or
+    initialisers(underlyingElement(this), unresolveElement(result), _, _) or
+    exprconv(unresolveElement(result), underlyingElement(this)) or
+    param_decl_bind(underlyingElement(this),_,unresolveElement(result))
   }
 
   /** Gets the closest `Element` enclosing this one. */
@@ -181,7 +185,7 @@ class Element extends @element {
         or
         result = exprEnclosingElement(this)
         or
-        var_decls(unresolveElement(this), unresolveElement(result), _, _, _)
+        var_decls(underlyingElement(this), unresolveElement(result), _, _, _)
       )
     )
   }
@@ -247,7 +251,7 @@ private predicate isFromUninstantiatedTemplateRec(Element e, Element template) {
  */
 class StaticAssert extends Locatable, @static_assert {
   override string toString() { result = "static_assert(..., \"" + getMessage() + "\")" }
-  Expr getCondition()    { static_asserts(unresolveElement(this), unresolveElement(result), _, _) }
-  string getMessage()    { static_asserts(unresolveElement(this), _, result, _) }
-  override Location getLocation() { static_asserts(unresolveElement(this), _, _, result) }
+  Expr getCondition()    { static_asserts(underlyingElement(this), unresolveElement(result), _, _) }
+  string getMessage()    { static_asserts(underlyingElement(this), _, result, _) }
+  override Location getLocation() { static_asserts(underlyingElement(this), _, _, result) }
 }

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

@@ -7,7 +7,7 @@ private import semmle.code.cpp.internal.Type
 class Enum extends UserType, IntegralOrEnumType {
   /** Gets an enumerator of this enumeration. */
   EnumConstant getAnEnumConstant() { result.getDeclaringEnum() = this }
-  EnumConstant getEnumConstant(int index) { enumconstants(unresolveElement(result),unresolveElement(this),index,_,_,_) }
+  EnumConstant getEnumConstant(int index) { enumconstants(unresolveElement(result),underlyingElement(this),index,_,_,_) }
 
   /**
    * Gets a descriptive string for the enum. This method is only intended to
@@ -24,15 +24,15 @@ class Enum extends UserType, IntegralOrEnumType {
    * For example: `enum E : int`.
    */
   predicate hasExplicitUnderlyingType() {
-    derivations(_, unresolveElement(this), _, _, _)
+    derivations(_, underlyingElement(this), _, _, _)
   }
 
   /**
    * The type of the enum-base [N4140 7.2], if it is specified.
    * For example: `int` in `enum E : int`.
    */
   Type getExplicitUnderlyingType() {
-    derivations(_, unresolveElement(this), _, unresolveElement(result), _)
+    derivations(_, underlyingElement(this), _, unresolveElement(result), _)
   }
 }
 
@@ -72,7 +72,7 @@ class NestedEnum extends Enum {
  */
 class ScopedEnum extends Enum {
   ScopedEnum() {
-    usertypes(unresolveElement(this),_,13)
+    usertypes(underlyingElement(this),_,13)
   }
 }
 
@@ -87,7 +87,7 @@ class EnumConstant extends Declaration, @enumconstant {
   /**
    * Gets the enumeration of which this enumerator is a member.
    */
-  Enum getDeclaringEnum() { enumconstants(unresolveElement(this),unresolveElement(result),_,_,_,_) }
+  Enum getDeclaringEnum() { enumconstants(underlyingElement(this),unresolveElement(result),_,_,_,_) }
 
   override Class getDeclaringType() {
     result = this.getDeclaringEnum().getDeclaringType()
@@ -96,7 +96,7 @@ class EnumConstant extends Declaration, @enumconstant {
   /**
    * Gets the name of this enumerator.
    */
-  override string getName() { enumconstants(unresolveElement(this),_,_,_,result,_) }
+  override string getName() { enumconstants(underlyingElement(this),_,_,_,result,_) }
 
   /**
    * Gets the value that this enumerator is initialized to, as a
@@ -106,13 +106,13 @@ class EnumConstant extends Declaration, @enumconstant {
   string getValue() { result = this.getInitializer().getExpr().getValue() }
 
   /** Gets the type of this enumerator. */
-  Type getType() { enumconstants(unresolveElement(this),_,_,unresolveElement(result),_,_) }
+  Type getType() { enumconstants(underlyingElement(this),_,_,unresolveElement(result),_,_) }
 
   /** Gets the location of a declaration of this enumerator. */
   override Location getADeclarationLocation() { result = this.getDefinitionLocation() }
 
   /** Gets the location of the definition of this enumerator. */
-  override Location getDefinitionLocation() { enumconstants(unresolveElement(this),_,_,_,_,result) }
+  override Location getDefinitionLocation() { enumconstants(underlyingElement(this),_,_,_,_,result) }
 
   /** Gets the location of the definition of this enumerator. */
   override Location getLocation() { result = this.getDefinitionLocation() }
@@ -124,7 +124,7 @@ class EnumConstant extends Declaration, @enumconstant {
   EnumConstantAccess getAnAccess() { result.getTarget() = this }
 
   /** Gets a specifier of this enumerator. */
-  override Specifier getASpecifier() { varspecifiers(unresolveElement(this),unresolveElement(result)) }
+  override Specifier getASpecifier() { varspecifiers(underlyingElement(this),unresolveElement(result)) }
 
   /**
    * An attribute of this enumerator.
@@ -133,6 +133,6 @@ class EnumConstant extends Declaration, @enumconstant {
    * which is only supported by Clang.
    */
   Attribute getAnAttribute() {
-    varattributes(unresolveElement(this), unresolveElement(result))
+    varattributes(underlyingElement(this), unresolveElement(result))
   }
 }