C++: Force unique resolveClass results

Author: jbj

cpp/ql/src/semmle/code/cpp/internal/ResolveClass.qll

@@ -1,23 +1,28 @@
 import semmle.code.cpp.Type
 
-/** Holds if `d` is a complete class named `name`. */
+pragma[noinline]
+private string getTopLevelClassName(@usertype c) {
+  isClass(c) and
+  usertypes(c, result, _)
+}
+
+/** Holds if `d` is a unique complete class named `name`. */
 pragma[noinline]
 private predicate existsCompleteWithName(string name, @usertype d) {
-  isClass(d) and
   is_complete(d) and
-  usertypes(d, name, _)
+  name = getTopLevelClassName(d) and
+  strictcount(@usertype other | is_complete(other) and getTopLevelClassName(other) = name) = 1
 }
 
 /** Holds if `c` is an incomplete class named `name`. */
 pragma[noinline]
 private predicate existsIncompleteWithName(string name, @usertype c) {
-  isClass(c) and
   not is_complete(c) and
-  usertypes(c, name, _)
+  name = getTopLevelClassName(c)
 }
 
 /**
- * Holds if `c` is an imcomplete class, and there exists a complete class `d`
+ * Holds if `c` is an imcomplete class, and there exists a unique complete class `d`
  * with the same name.
  */
 private predicate hasCompleteTwin(@usertype c, @usertype d) {
@@ -30,10 +35,8 @@ private predicate hasCompleteTwin(@usertype c, @usertype d) {
 import Cached
 cached private module Cached {
   /**
-   * If `c` is incomplete, and there exists a complete class with the same name,
-   * then the result is that complete class. Otherwise, the result is `c`. If
-   * multiple complete classes have the same name, this predicate may have
-   * multiple results.
+   * If `c` is incomplete, and there exists a unique complete class with the same name,
+   * then the result is that complete class. Otherwise, the result is `c`.
    */
   cached @usertype resolveClass(@usertype c) {
     hasCompleteTwin(c, result)

cpp/ql/test/library-tests/structs/incomplete_definition/pointerbasetype.expected

@@ -1,11 +1,7 @@
-| a.h:5:8:5:13 | cheese | x.cpp:6:10:6:12 | Foo | 3 |
-| a.h:5:8:5:13 | cheese | x.cpp:12:9:12:11 | Foo | 3 |
+| a.h:5:8:5:13 | cheese | a.h:2:8:2:10 | Foo | 0 |
 | a.h:5:8:5:13 | cheese | y.cpp:4:8:4:10 | Foo | 3 |
 | x.cpp:3:6:3:10 | bar_x | a.h:4:8:4:10 | Bar | 3 |
-| x.cpp:19:6:19:10 | foo_x | x.cpp:6:10:6:12 | Foo | 3 |
-| x.cpp:19:6:19:10 | foo_x | x.cpp:12:9:12:11 | Foo | 3 |
-| x.cpp:19:6:19:10 | foo_x | y.cpp:4:8:4:10 | Foo | 3 |
+| x.cpp:19:6:19:10 | foo_x | a.h:2:8:2:10 | Foo | 0 |
 | x.cpp:23:5:23:17 | templateField | x.cpp:6:10:6:12 | Foo | 3 |
 | x.cpp:23:5:23:17 | templateField | x.cpp:12:9:12:11 | Foo | 3 |
-| x.cpp:26:18:26:29 | template_foo | x.cpp:22:7:22:14 | Template<Foo *> | 3 |
-| x.cpp:26:18:26:29 | template_foo | x.cpp:22:7:22:14 | Template<Foo *> | 3 |
+| x.cpp:26:18:26:29 | template_foo | x.cpp:22:7:22:14 | Template<Foo *> | 0 |

cpp/ql/test/library-tests/structs/qualified_names/pointerBaseType.expected

@@ -1,6 +1,4 @@
-| decls.cpp:4:6:4:6 | x | defs.cpp:2:9:2:9 | C |
-| decls.cpp:4:6:4:6 | x | defs.cpp:7:9:7:9 | C |
+| decls.cpp:4:6:4:6 | x | decls.cpp:2:9:2:9 | C |
 | defs.cpp:18:21:18:38 | definedAndDeclared | defs.cpp:11:7:11:24 | DefinedAndDeclared |
-| defs.cpp:25:28:25:32 | mdbsh | c1.cpp:3:8:3:32 | MultipleDefsButSameHeader |
-| defs.cpp:25:28:25:32 | mdbsh | c2.cpp:3:8:3:32 | MultipleDefsButSameHeader |
+| defs.cpp:25:28:25:32 | mdbsh | header.h:1:8:1:32 | MultipleDefsButSameHeader |
 | defs.cpp:29:24:29:28 | odidf | c1.cpp:7:8:7:28 | OneDefInDifferentFile |