C++: Tests for variables with ambiguous types

Author: jbj

cpp/ql/test/library-tests/multiple_declarations/variable_types/extracted_once.h

@@ -0,0 +1,16 @@
+// This header file is extracted only once even though it's included by both
+// file1.c and file2.c. That's presumably because it's wrongly considered to
+// expand to the same trap in both contexts. In practice, this header gets
+// extracted together with the extraction of file1.c.
+
+// BUG: types of members depend on extraction order.
+// Only one copy of this struct is extracted, and the types of its members refer
+// to the typedefs in file1.c. Had file2.c been extracted first instead, the
+// types of its members would be different.
+struct UnifiableOnce {
+    intAlias intMember;
+    qualifiedIntAlias qualifiedIntMember;
+};
+
+// BUG: types of parameters depend on extraction order.
+void functionOnce(intAlias param);

cpp/ql/test/library-tests/multiple_declarations/variable_types/extracted_twice.h

@@ -0,0 +1,30 @@
+// This header file is extracted twice because its inclusions in file1.c and
+// file2.c lead to different context hashes, seemingly because this file (unlike
+// extracted_once.h) refers to `structAlias`. That means the resulting trap has
+// two copies of all declarations in this file, and those copies have to be
+// unified in the trap import step or in QL.
+
+// GOOD. The types of the members of this struct are unifiable, which in this
+// context means that they share the same unspecified types. This means that the
+// two extractions of the struct get the same content hash and therefore become
+// one entry in the database. Both struct members have multiple types in the
+// `membervariables` table, but those are unified in the
+// `MemberVariable.getType()` predicate.
+struct UnifiableTwice {
+    intAlias intMember;
+    qualifiedIntAlias qualifiedIntMember;
+};
+
+// BUG: Non-member variables of this type have two types in the database.
+// The type of `structMember` is ambiguous, and the two possible types are not
+// unifiable, meaning in this context that they don't share an unspecified type.
+// The types are nevertheless _compatible_, so it's valid C (not C++) to use
+// these two definitions interchangably in the same program.
+struct NotUnifiableTwice {
+    structAlias structMember;
+};
+
+// BUG: The parameter of this function has two types.
+// Because the `MemberVariable.getType()` workaround does not apply to a
+// `Parameter`, this `Parameter` gets two types.
+void functionTwice(intAlias param);

cpp/ql/test/library-tests/multiple_declarations/variable_types/file1.c

@@ -0,0 +1,15 @@
+// These typedefs are all _compatible_ (see
+// https://en.cppreference.com/w/c/language/type#Compatible_types) with their
+// siblings in file2.c. It varies whether they have a canonical form that's
+// common to them both.
+typedef int localInt;
+typedef localInt intAlias; // has common `getUnderlyingType()` and `getUnspecifiedType()`
+typedef int qualifiedIntAlias; // only has common `getUnspecifiedType()`
+typedef struct emptyStruct1 { } structAlias; // has no common type
+
+#include "extracted_once.h"
+struct UnifiableOnce uOnce;
+
+#include "extracted_twice.h"
+struct UnifiableTwice uTwice;
+struct NotUnifiableTwice nTwice; // BUG: this variable has two types

cpp/ql/test/library-tests/multiple_declarations/variable_types/file2.c

@@ -0,0 +1,10 @@
+typedef int intAlias;
+typedef const int qualifiedIntAlias;
+typedef struct emptyStruct2 { } structAlias;
+
+#include "extracted_once.h"
+struct UnifiableOnce uOnce;
+
+#include "extracted_twice.h"
+struct UnifiableTwice uTwice;
+struct NotUnifiableTwice nTwice; // BUG: this variable has two types

cpp/ql/test/library-tests/multiple_declarations/variable_types/varType.expected

@@ -0,0 +1,17 @@
+| extracted_once.h:11:14:11:22 | intMember | file1.c:6:18:6:25 | intAlias | 1 |
+| extracted_once.h:12:23:12:40 | qualifiedIntMember | file1.c:7:13:7:29 | qualifiedIntAlias | 1 |
+| extracted_once.h:16:28:16:32 | param | file1.c:6:18:6:25 | intAlias | 1 |
+| extracted_twice.h:14:14:14:22 | intMember | file://:0:0:0:0 | int | 1 |
+| extracted_twice.h:15:23:15:40 | qualifiedIntMember | file://:0:0:0:0 | int | 1 |
+| extracted_twice.h:24:17:24:28 | structMember | file1.c:8:33:8:43 | structAlias | 1 |
+| extracted_twice.h:24:17:24:28 | structMember | file2.c:3:33:3:43 | structAlias | 1 |
+| extracted_twice.h:30:29:30:33 | param | file1.c:6:18:6:25 | intAlias | 2 |
+| extracted_twice.h:30:29:30:33 | param | file2.c:1:13:1:20 | intAlias | 2 |
+| file1.c:11:22:11:26 | uOnce | extracted_once.h:10:8:10:20 | UnifiableOnce | 1 |
+| file1.c:14:23:14:28 | uTwice | extracted_twice.h:13:8:13:21 | UnifiableTwice | 1 |
+| file1.c:15:26:15:31 | nTwice | extracted_twice.h:23:8:23:24 | NotUnifiableTwice | 2 |
+| file1.c:15:26:15:31 | nTwice | extracted_twice.h:23:8:23:24 | NotUnifiableTwice | 2 |
+| file2.c:6:22:6:26 | uOnce | extracted_once.h:10:8:10:20 | UnifiableOnce | 1 |
+| file2.c:9:23:9:28 | uTwice | extracted_twice.h:13:8:13:21 | UnifiableTwice | 1 |
+| file2.c:10:26:10:31 | nTwice | extracted_twice.h:23:8:23:24 | NotUnifiableTwice | 2 |
+| file2.c:10:26:10:31 | nTwice | extracted_twice.h:23:8:23:24 | NotUnifiableTwice | 2 |

cpp/ql/test/library-tests/multiple_declarations/variable_types/varType.ql

@@ -0,0 +1,5 @@
+import cpp
+
+from Variable var
+where exists(var.getFile().getRelativePath())
+select var, var.getType(), strictcount(var.getType())