[analyzer] pr37802: Fix symbolic-pointer-to-boolean casts during load.

[NoQ]

Summary

The canonical way to represent the result of casting &SymRegion{$x} to bool is ($x != 0), not $x. In fact $x is an ill-formed SVal (when`$x` is a loc-type symbol) and it gets caught by D48205. Fix the cast procedure.

Because our cast code is a spaghetti, the code that was fixed was in fact executed very rarely, because there's a duplicate guard in evalCast() that's written correctly. But when evalCastFromLoc() is called directly (eg., from CastRetrievedVal()), this becomes a problem.

Fixes https://bugs.llvm.org/show_bug.cgi?id=37802.

cfe/trunk/lib/StaticAnalyzer/Core/SimpleSValBuilder.cpp

switch (val.getSubKind()) {
           if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(FTR->getDecl()))
             if (FD->isWeak())
               // FIXME: Currently we are using an extent symbol here,
               // because there are no generic region address metadata
               // symbols to use, only content metadata.
               return nonloc::SymbolVal(SymMgr.getExtentSymbol(FTR));
 
         if (const SymbolicRegion *SymR = R->getSymbolicBase())
-          return nonloc::SymbolVal(SymR->getSymbol());
+          return makeNonLoc(SymR->getSymbol(), BO_NE,
+                            BasicVals.getZeroWithPtrWidth(), castTy);
 
         // FALL-THROUGH
         LLVM_FALLTHROUGH;
       }
 
       case loc::GotoLabelKind:
         // Labels and non-symbolic memory regions are always true.
         return makeTruthVal(true, castTy);

cfe/trunk/test/Analysis/casts.cpp

 }
 
 int *&&castToIntPtrRValueRef(char *p) {
   return (int *&&)*(int *)p;
 }
 bool testCastToIntPtrRValueRef(char *p, int *s) {
   return castToIntPtrRValueRef(p) != s; // no-crash
 }
+
+bool retrievePointerFromBoolean(int *p) {
+  bool q;
+  *reinterpret_cast<int **>(&q) = p;
+  return q;
+}

cfe/trunk/test/Analysis/pr37802.cpp

+// RUN: %clang_analyze_cc1 -w -analyzer-checker=core -verify %s
+
+// expected-no-diagnostics
+
+void *operator new(unsigned long, void *h) { return h; }
+
+// I've no idea what this code does, but it used to crash, so let's keep it.
+namespace pr37802_v1 {
+struct J {
+  int *p;
+};
+class X {
+  void *ar;
+
+public:
+  X(void *t) : ar(t) {}
+  template <typename T>
+  void f(const T &t) {
+    new (ar) T(t);
+  }
+};
+class Y {
+public:
+  template <typename T>
+  void f(T &&);
+  void f(J t) {
+    f(*t.p);
+  }
+};
+class Z {
+  int at() const {}
+
+public:
+  Z(const Z &other) {
+    other.au(X(this));
+  }
+  template <typename T>
+  void au(T t) const {
+    void *c = const_cast<Z *>(this);
+    if (at()) {
+      t.f(*static_cast<J *>(c));
+    } else {
+      t.f(*static_cast<bool *>(c));
+    }
+  }
+};
+Z g() {
+  Z az = g();
+  Z e = az;
+  Y d;
+  e.au(d);
+}
+} // namespace pr37802_v1
+
+
+// This slightly modified code crashed differently.
+namespace pr37802_v2 {
+struct J {
+  int *p;
+};
+
+class X {
+  void *ar;
+
+public:
+  X(void *t) : ar(t) {}
+  void f(const J &t) { new (ar) J(t); }
+  void f(const bool &t) { new (ar) bool(t); }
+};
+
+class Y {
+public:
+  void boolf(bool &&);
+  void f(J &&);
+  void f(J t) { boolf(*t.p); }
+};
+
+class Z {
+  int at() const {}
+
+public:
+  Z(const Z &other) { other.au(X(this)); }
+  void au(X t) const {
+    void *c = const_cast<Z *>(this);
+    if (at()) {
+      t.f(*static_cast<J *>(c));
+    } else {
+      t.f(*static_cast<bool *>(c));
+    }
+  }
+  void au(Y t) const {
+    void *c = const_cast<Z *>(this);
+    if (at()) {
+      t.f(*static_cast<J *>(c));
+    } else {
+    }
+  }
+};
+
+Z g() {
+  Z az = g();
+  Z e = az;
+  Y d;
+  e.au(d);
+}
+} // namespace pr37802_v2