Until we can make the dead stores checker smarter, dont' emit dead store warnings for C++ objects (whose constructors/destructors have possible side-effects).

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@91412 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 24 insertions, 0 deletions

diff --git a/lib/Analysis/CheckDeadStores.cpp b/lib/Analysis/CheckDeadStores.cpp
index ec13328447..db9016fa1e 100644
--- a/lib/Analysis/CheckDeadStores.cpp
+++ b/lib/Analysis/CheckDeadStores.cpp
@@ -186,6 +186,10 @@ public:
 
         if (V->hasLocalStorage())
           if (Expr* E = V->getInit()) {
+            // Don't warn on C++ objects (yet) until we can show that their
+            // constructors/destructors don't have side effects.
+            if (isa<CXXConstructExpr>(E))
+              return;
             // A dead initialization is a variable that is dead after it
             // is initialized.  We don't flag warnings for those variables
             // marked 'unused'.
diff --git a/test/Analysis/dead-stores.cpp b/test/Analysis/dead-stores.cpp
index 1bab9f4bad..363cfdd98c 100644
--- a/test/Analysis/dead-stores.cpp
+++ b/test/Analysis/dead-stores.cpp
@@ -4,6 +4,10 @@
 // RUN: clang -cc1 -analyze -analyzer-experimental-internal-checks -checker-cfref -analyzer-store=region -analyzer-constraints=basic -warn-dead-stores -verify %s
 // RUN: clang -cc1 -analyze -analyzer-experimental-internal-checks -checker-cfref -analyzer-store=region -analyzer-constraints=range -warn-dead-stores -verify %s
 
+//===----------------------------------------------------------------------===//
+// Basic dead store checking (but in C++ mode).
+//===----------------------------------------------------------------------===//
+
 int j;
 void f1() {
   int x = 4;
@@ -17,3 +21,19 @@ void f1() {
     break;
   }
 }
+
+//===----------------------------------------------------------------------===//
+// Dead store checking involving constructors.
+//===----------------------------------------------------------------------===//
+
+class Test1 {
+  int &x;
+public:
+  Test1(int &y) : x(y) {}
+  ~Test1() { ++x; }
+};
+
+int test_ctor_1(int x) {
+  { Test1 a(x); } // no-warning
+  return x;
+}