[analyzer] Improve modeling of static initializers.

Conversions between unrelated pointer types (e.g. char * and void *) involve
bitcasts which were not properly modeled in case of static initializers. The
patch fixes this problem.

The problem was originally spotted by Artem Dergachev. Patched by Yuri Gribov!

Differential Revision: http://reviews.llvm.org/D14652

llvm-svn: 253532

2 files changed, 18 insertions, 5 deletions

diff --git a/clang/lib/StaticAnalyzer/Core/SValBuilder.cpp b/clang/lib/StaticAnalyzer/Core/SValBuilder.cpp
index 4f8ccd0329d..98fac33c22a 100644
--- a/clang/lib/StaticAnalyzer/Core/SValBuilder.cpp
+++ b/clang/lib/StaticAnalyzer/Core/SValBuilder.cpp
@@ -275,11 +275,17 @@ Optional<SVal> SValBuilder::getConstantVal(const Expr *E) {
 
   case Stmt::ImplicitCastExprClass: {
     const CastExpr *CE = cast<CastExpr>(E);
-    if (CE->getCastKind() == CK_ArrayToPointerDecay) {
-      Optional<SVal> ArrayVal = getConstantVal(CE->getSubExpr());
-      if (!ArrayVal)
+    switch (CE->getCastKind()) {
+    default:
+      break;
+    case CK_ArrayToPointerDecay:
+    case CK_BitCast: {
+      const Expr *SE = CE->getSubExpr();
+      Optional<SVal> Val = getConstantVal(SE);
+      if (!Val)
         return None;
-      return evalCast(*ArrayVal, CE->getType(), CE->getSubExpr()->getType());
+      return evalCast(*Val, CE->getType(), SE->getType());
+    }
     }
     // FALLTHROUGH
   }
diff --git a/clang/test/Analysis/inline.cpp b/clang/test/Analysis/inline.cpp
index 183df16e124..b7962b53a89 100644
--- a/clang/test/Analysis/inline.cpp
+++ b/clang/test/Analysis/inline.cpp
@@ -275,7 +275,7 @@ namespace DefaultArgs {
 
     clang_analyzer_eval(defaultReferenceZero(1) == -1); // expected-warning{{TRUE}}
     clang_analyzer_eval(defaultReferenceZero() == 0); // expected-warning{{TRUE}}
-}
+  }
 
   double defaultFloatReference(const double &i = 42) {
     return -i;
@@ -300,6 +300,13 @@ namespace DefaultArgs {
     clang_analyzer_eval(defaultString("xyz") == 'y'); // expected-warning{{TRUE}}
     clang_analyzer_eval(defaultString() == 'b'); // expected-warning{{TRUE}}
   }
+
+  const void * const void_string = "abc";
+
+  void testBitcastedString() {
+    clang_analyzer_eval(0 != void_string); // expected-warning{{TRUE}}
+    clang_analyzer_eval('b' == ((char *)void_string)[1]); // expected-warning{{TRUE}}
+  }
 }
 
 namespace OperatorNew {