C++: Add support for C++ using aliases

Matthew Gretton-Dann · Matthew Gretton-Dann · commit 5468b8def75a · 2019-09-23T13:57:50.000+01:00
Previously these were identified as typedefs.
diff --git a/cpp/ql/src/semmle/code/cpp/TypedefType.qll b/cpp/ql/src/semmle/code/cpp/TypedefType.qll
@@ -3,11 +3,18 @@ private import semmle.code.cpp.internal.ResolveClass
 
 /**
  * A C/C++ typedef type. See 4.9.1.
+ *
+ * Represents either of the following typedef styles:
+ *
+ *   * CTypedefType: typedef <type> <name>;
+ *   * UsingAliasTypedefType: using <name> = <type>;
  */
 class TypedefType extends UserType {
-  TypedefType() { usertypes(underlyingElement(this), _, 5) }
 
-  override string getCanonicalQLClass() { result = "TypedefType" }
+  TypedefType() {
+    usertypes(underlyingElement(this),_,5) or
+    usertypes(underlyingElement(this),_,14)
+  }
 
   /**
    * Gets the base type of this typedef type.
@@ -26,10 +33,6 @@ class TypedefType extends UserType {
     result = this.getBaseType().getPointerIndirectionLevel()
   }
 
-  override string explain() {
-    result = "typedef {" + this.getBaseType().explain() + "} as \"" + this.getName() + "\""
-  }
-
   override predicate isDeeplyConst() { this.getBaseType().isDeeplyConst() } // Just an alias
 
   override predicate isDeeplyConstBelow() { this.getBaseType().isDeeplyConstBelow() } // Just an alias
@@ -45,6 +48,34 @@ class TypedefType extends UserType {
   override Type stripType() { result = getBaseType().stripType() }
 }
 
+/**
+ * A traditional C/C++ typedef type. See 4.9.1.
+ */
+class CTypedefType extends TypedefType {
+
+  CTypedefType() {
+    usertypes(underlyingElement(this),_,5)
+  }
+
+  override string getCanonicalQLClass() { result = "CTypedefType" }
+
+  override string explain() { result =  "typedef {" + this.getBaseType().explain() + "} as \"" + this.getName() + "\"" }
+}
+
+/**
+ * A using alias C++ typedef type.
+ */
+class UsingAliasTypedefType extends TypedefType {
+
+  UsingAliasTypedefType() {
+    usertypes(underlyingElement(this),_,14)
+  }
+
+  override string getCanonicalQLClass() { result = "UsingAliasTypedefType" }
+
+  override string explain() { result =  "using {" + this.getBaseType().explain() + "} as \"" + this.getName() + "\"" }
+}
+
 /**
  * A C++ typedef type that is directly enclosed by a function.
  */
diff --git a/cpp/ql/src/semmlecode.cpp.dbscheme b/cpp/ql/src/semmlecode.cpp.dbscheme
@@ -675,7 +675,7 @@ decltypes(
   | 2 = class
   | 3 = union
   | 4 = enum
-  | 5 = typedef
+  | 5 = typedef                       // classic C: typedef typedef type name
   | 6 = template
   | 7 = template_parameter
   | 8 = template_template_parameter
@@ -684,6 +684,7 @@ decltypes(
 // ... 11 objc_protocol deprecated
 // ... 12 objc_category deprecated
   | 13 = scoped_enum
+  | 14 = using_alias                  // a using name = type style typedef
   ;
 */
 usertypes(
