[analyzer] Fix handling of "empty" structs with base classes

Summary:
RegionStoreManager had an optimization which replaces references to empty
structs with UnknownVal. Unfortunately, this check didn't take into account
possible field members in base classes.

To address this, I changed this test to "is empty and has no base classes". I
don't consider it worth the trouble to go through base classes and check if all
of them are empty.

Reviewers: jordan_rose

CC: cfe-commits

Differential Revision: http://llvm-reviews.chandlerc.com/D1547

llvm-svn: 189590

1 files changed, 23 insertions, 0 deletions

diff --git a/clang/test/Analysis/array-struct-region.cpp b/clang/test/Analysis/array-struct-region.cpp
index 12ae5d3..a776d7d 100644
--- a/clang/test/Analysis/array-struct-region.cpp
+++ b/clang/test/Analysis/array-struct-region.cpp
@@ -173,4 +173,27 @@ void testImmediateUseOp() {
   clang_analyzer_eval(getConstrainedFieldRefOp(getS()) == 42); // expected-warning{{TRUE}}
 }
 
+namespace EmptyClass {
+  struct Base {
+    int& x;
+
+    Base(int& x) : x(x) {}
+  };
+
+  struct Derived : public Base {
+    Derived(int& x) : Base(x) {}
+
+    void operator=(int a) { x = a; }
+  };
+
+  Derived ref(int& a) { return Derived(a); }
+
+  // There used to be a warning here, because analyzer treated Derived as empty.
+  int test() {
+    int a;
+    ref(a) = 42;
+    return a; // no warning
+  }
+}
+
 #endif