[clang][Interp] Fix expected values for Pointer API

Add a unit test for this.

Differential Revision: https://reviews.llvm.org/D158069

Author: tbaederr

clang/lib/AST/Interp/Context.h

@@ -86,6 +86,9 @@ class Context final {
     return false;
   }
 
+  /// Returns the program. This is only needed for unittests.
+  Program &getProgram() const { return *P.get(); }
+
 private:
   /// Runs a function.
   bool Run(State &Parent, const Function *Func, APValue &Result);

clang/lib/AST/Interp/Pointer.h

@@ -78,6 +78,15 @@ class Pointer {
   void operator=(const Pointer &P);
   void operator=(Pointer &&P);
 
+  /// Equality operators are just for tests.
+  bool operator==(const Pointer &P) const {
+    return Pointee == P.Pointee && Base == P.Base && Offset == P.Offset;
+  }
+
+  bool operator!=(const Pointer &P) const {
+    return Pointee != P.Pointee || Base != P.Base || Offset != P.Offset;
+  }
+
   /// Converts the pointer to an APValue.
   APValue toAPValue() const;
 
@@ -276,7 +285,8 @@ class Pointer {
   const Record *getRecord() const { return getFieldDesc()->ElemRecord; }
   /// Returns the element record type, if this is a non-primive array.
   const Record *getElemRecord() const {
-    return getFieldDesc()->ElemDesc->ElemRecord;
+    const Descriptor *ElemDesc = getFieldDesc()->ElemDesc;
+    return ElemDesc ? ElemDesc->ElemRecord : nullptr;
   }
   /// Returns the field information.
   const FieldDecl *getField() const { return getFieldDesc()->asFieldDecl(); }
@@ -326,6 +336,11 @@ class Pointer {
   int64_t getIndex() const {
     if (isElementPastEnd())
       return 1;
+
+    // narrow()ed element in a composite array.
+    if (Base > 0 && Base == Offset)
+      return 0;
+
     if (auto ElemSize = elemSize())
       return getOffset() / ElemSize;
     return 0;

clang/unittests/AST/CMakeLists.txt

@@ -5,6 +5,8 @@ set(LLVM_LINK_COMPONENTS
   )
 
 
+add_subdirectory(Interp)
+
 add_clang_unittest(ASTTests
   ASTContextParentMapTest.cpp
   ASTExprTest.cpp

clang/unittests/AST/Interp/CMakeLists.txt

@@ -0,0 +1,14 @@
+add_clang_unittest(InterpTests
+  Descriptor.cpp
+  )
+
+clang_target_link_libraries(InterpTests
+  PRIVATE
+  clangAST
+  clangBasic
+  )
+
+  target_link_libraries(InterpTests
+  PRIVATE
+  clangTesting
+)