Merging r311182:

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r311182 | alexshap | 2017-08-18 11:20:43 -0700 (Fri, 18 Aug 2017) | 22 lines

[analyzer] Fix modeling of constructors

This diff fixes analyzer's crash (triggered assert) on the newly added test case.
The assert being discussed is assert(!B.lookup(R, BindingKey::Direct))
in lib/StaticAnalyzer/Core/RegionStore.cpp, however the root cause is different.
For classes with empty bases the offsets might be tricky.
For example, let's assume we have
 struct S: NonEmptyBase, EmptyBase {
     ...
 };
In this case Clang applies empty base class optimization and 
the offset of EmptyBase will be 0, it can be verified via
clang -cc1 -x c++ -v -fdump-record-layouts main.cpp -emit-llvm -o /dev/null.
When the analyzer tries to perform zero initialization of EmptyBase
it will hit the assert because that region
has already been "written" by the constructor of NonEmptyBase.

Test plan:
make check-all

Differential revision: https://reviews.llvm.org/D36851

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git-svn-id: https://llvm.org/svn/llvm-project/cfe/branches/release_50@311378 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 17 insertions, 0 deletions

diff --git a/test/Analysis/ctor.mm b/test/Analysis/ctor.mm
index 646229aac9..619e2cb0f0 100644
--- a/test/Analysis/ctor.mm
+++ b/test/Analysis/ctor.mm
@@ -704,3 +704,20 @@ namespace PR19579 {
     };
   }
 }
+
+namespace NoCrashOnEmptyBaseOptimization {
+  struct NonEmptyBase {
+    int X;
+    explicit NonEmptyBase(int X) : X(X) {}
+  };
+
+  struct EmptyBase {};
+
+  struct S : NonEmptyBase, EmptyBase {
+    S() : NonEmptyBase(0), EmptyBase() {}
+  };
+
+  void testSCtorNoCrash() {
+    S s;
+  }
+}