[analyzer] CallEvent: Add partially working methods for obtaining the callee stack frame.

[NoQ]

Summary

These methods allow reasoning about the stack frame that will be (or was) used when the function will be (or was) inlined, even if it will not be (or was not) inlined.

They are implemented in a fairly ugly manner, and while i plan to address some of the issues in follow-up patches (at least, do something about virtual calls), i don't think it'll work perfectly soon. A proper implementation would require a large amount of refactoring for Call::getDecl() and Call::getRuntimeDefinition() and the logic in ExprEngine's call modeling and i didn't accomplish much in a couple days of working on it, so i'm putting a proper implementation on hold for now, safely returning nullptr when the proper Decl cannot be reliably obtained.

This was ultimately necessary to obtain the parameter regions on the future stack frame for the purposes of D49443. We don't need this function to be perfect because a lot of other things are imperfect and we're fine with falling back to a conservative behavior.

[george.karpenkov]

Minor nits mostly.

include/clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h

411 ↗

(On Diff #156957)

Could we be more succinct here?
e.g. \return Best-effort getter for AnalysisDeclContext, returns null on failure.

Same for all the methods below.

include/clang/StaticAnalyzer/Core/PathSensitive/ExprEngine.h

776 ↗

(On Diff #156957)

Could we group it with other public methods at the top?

lib/StaticAnalyzer/Core/CallEvent.cpp

193 ↗

(On Diff #156957)

"we cannot have" comments seem redundant, it's usually implied by the code.
This one is up to you though.

197 ↗

(On Diff #156957)

Can we remove "maybe" / "that would have been" comments?

[NoQ]

Address comments by editing comments.

[NoQ]

lib/StaticAnalyzer/Core/CallEvent.cpp

197 ↗

(On Diff #156957)

Changed them into a TODO because they're rather important to keep. Like, that's a flaw in this code.

[NoQ]

Add one more handy method, getAdjustedParameterIndex(), which helps using getParameterLocation().

[NoQ]

cfe/trunk/include/clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h

431

Whoops, this is wrong: should say getLocationContext().

cfe/trunk/include/clang/Analysis/ConstructionContext.h

ConstructionContextItem(const CallExpr *CE, unsigned Index)
       : Data(CE), Kind(ArgumentKind), Index(Index) {}
 
   ConstructionContextItem(const CXXConstructExpr *CE, unsigned Index)
       : Data(CE), Kind(ArgumentKind), Index(Index) {}
 
   ConstructionContextItem(const ObjCMessageExpr *ME, unsigned Index)
       : Data(ME), Kind(ArgumentKind), Index(Index) {}
 
+  // A polymorphic version of the previous calls with dynamic type check.
+  ConstructionContextItem(const Expr *E, unsigned Index)
+      : Data(E), Kind(ArgumentKind), Index(Index) {
+    assert(isa<CallExpr>(E) || isa<CXXConstructExpr>(E) ||
+           isa<ObjCMessageExpr>(E));
+  }
+
   ConstructionContextItem(const CXXCtorInitializer *Init)
       : Data(Init), Kind(InitializerKind), Index(0) {}
 
   ItemKind getKind() const { return Kind; }
 
   LLVM_DUMP_METHOD StringRef getKindAsString() const {
     return getKindAsString(getKind());
   }

cfe/trunk/include/clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h

 #include "clang/AST/ExprCXX.h"
 #include "clang/AST/ExprObjC.h"
 #include "clang/AST/Stmt.h"
 #include "clang/AST/Type.h"
 #include "clang/Basic/IdentifierTable.h"
 #include "clang/Basic/LLVM.h"
 #include "clang/Basic/SourceLocation.h"
 #include "clang/Basic/SourceManager.h"
+#include "clang/StaticAnalyzer/Core/PathSensitive/ExprEngine.h"
 #include "clang/StaticAnalyzer/Core/PathSensitive/ProgramState.h"
 #include "clang/StaticAnalyzer/Core/PathSensitive/ProgramState_Fwd.h"
 #include "clang/StaticAnalyzer/Core/PathSensitive/SVals.h"
 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/IntrusiveRefCntPtr.h"
 #include "llvm/ADT/PointerIntPair.h"
 #include "llvm/ADT/PointerUnion.h"
 #include "llvm/ADT/STLExtras.h"
public:
   /// This will return a null QualType if the result type cannot be determined.
   static QualType getDeclaredResultType(const Decl *D);
 
   /// Returns true if the given decl is known to be variadic.
   ///
   /// \p D must not be null.
   static bool isVariadic(const Decl *D);
 
+  /// Returns AnalysisDeclContext for the callee stack frame.
+  /// Currently may fail; returns null on failure.
+  AnalysisDeclContext *getCalleeAnalysisDeclContext() const;
+
+  /// Returns the callee stack frame. That stack frame will only be entered
+  /// during analysis if the call is inlined, but it may still be useful
+  /// in intermediate calculations even if the call isn't inlined.
+  /// May fail; returns null on failure.
+  const StackFrameContext *getCalleeStackFrame() const;
+
+  /// Returns memory location for a parameter variable within the callee stack
+  /// frame. May fail; returns null on failure.
+  const VarRegion *getParameterLocation(unsigned Index) const;
+
+  /// Returns true if on the current path, the argument was constructed by
+  /// calling a C++ constructor over it. This is an internal detail of the
+  /// analysis which doesn't necessarily represent the program semantics:
+  /// if we are supposed to construct an argument directly, we may still
+  /// not do that because we don't know how (i.e., construction context is
+  /// unavailable in the CFG or not supported by the analyzer).
+  bool isArgumentConstructedDirectly(unsigned Index) const {
+    // This assumes that the object was not yet removed from the state.
+    return ExprEngine::getObjectUnderConstruction(
+        getState(), {getOriginExpr(), Index}, getCalleeStackFrame()).hasValue();
+  }
+
+  /// Some calls have parameter numbering mismatched from argument numbering.
+  /// This function converts an argument index to the corresponding
+  /// parameter index. Returns None is the argument doesn't correspond
+  /// to any parameter variable.
+  Optional<unsigned> getAdjustedParameterIndex(unsigned ArgumentIndex) const {
+    if (dyn_cast_or_null<CXXOperatorCallExpr>(getOriginExpr()) &&
+        dyn_cast_or_null<CXXMethodDecl>(getDecl())) {
+      // For member operator calls argument 0 on the expression corresponds
+      // to implicit this-parameter on the declaration.
+      return (ArgumentIndex > 0) ? Optional<unsigned>(ArgumentIndex - 1) : None;
+    }
+    return ArgumentIndex;
+  }
+
   // Iterator access to formal parameters and their types.
 private:
   struct GetTypeFn {
     QualType operator()(ParmVarDecl *PD) const { return PD->getType(); }
   };
 
 public:
   /// Return call's formal parameters.

cfe/trunk/include/clang/StaticAnalyzer/Core/PathSensitive/ExprEngine.h

return R.isValid() ? svalBuilder.evalBinOpNN(state, op, L,
                                                  R.castAs<NonLoc>(), T) : R;
   }
 
   SVal evalBinOp(ProgramStateRef ST, BinaryOperator::Opcode Op,
                  SVal LHS, SVal RHS, QualType T) {
     return svalBuilder.evalBinOp(ST, Op, LHS, RHS, T);
   }
 
+  /// By looking at a certain item that may be potentially part of an object's
+  /// ConstructionContext, retrieve such object's location. A particular
+  /// statement can be transparently passed as \p Item in most cases.
+  static Optional<SVal>
+  getObjectUnderConstruction(ProgramStateRef State,
+                             const ConstructionContextItem &Item,
+                             const LocationContext *LC);
+
 protected:
   /// evalBind - Handle the semantics of binding a value to a specific location.
   ///  This method is used by evalStore, VisitDeclStmt, and others.
   void evalBind(ExplodedNodeSet &Dst, const Stmt *StoreE, ExplodedNode *Pred,
                 SVal location, SVal Val, bool atDeclInit = false,
                 const ProgramPoint *PP = nullptr);
 
   /// Call PointerEscape callback when a value escapes as a result of bind.
private:
 
   /// Mark the object sa fully constructed, cleaning up the state trait
   /// that tracks objects under construction.
   static ProgramStateRef
   finishObjectConstruction(ProgramStateRef State,
                            const ConstructionContextItem &Item,
                            const LocationContext *LC);
 
-  /// If the given statement corresponds to an object under construction,
-  /// being part of its construciton context, retrieve that object's location.
-  static Optional<SVal>
-  getObjectUnderConstruction(ProgramStateRef State,
-                             const ConstructionContextItem &Item,
-                             const LocationContext *LC);
-
   /// If the given expression corresponds to a temporary that was used for
   /// passing into an elidable copy/move constructor and that constructor
   /// was actually elided, track that we also need to elide the destructor.
   static ProgramStateRef elideDestructor(ProgramStateRef State,
                                          const CXXBindTemporaryExpr *BTE,
                                          const LocationContext *LC);
 
   /// Stop tracking the destructor that corresponds to an elided constructor.

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

 #include "clang/AST/Expr.h"
 #include "clang/AST/ExprCXX.h"
 #include "clang/AST/ExprObjC.h"
 #include "clang/AST/ParentMap.h"
 #include "clang/AST/Stmt.h"
 #include "clang/AST/Type.h"
 #include "clang/Analysis/AnalysisDeclContext.h"
 #include "clang/Analysis/CFG.h"
+#include "clang/Analysis/CFGStmtMap.h"
 #include "clang/Analysis/ProgramPoint.h"
 #include "clang/CrossTU/CrossTranslationUnit.h"
 #include "clang/Basic/IdentifierTable.h"
 #include "clang/Basic/LLVM.h"
 #include "clang/Basic/SourceLocation.h"
 #include "clang/Basic/SourceManager.h"
 #include "clang/Basic/Specifiers.h"
 #include "clang/StaticAnalyzer/Core/BugReporter/PathDiagnostic.h"

 bool CallEvent::isGlobalCFunction(StringRef FunctionName) const {
   const auto *FD = dyn_cast_or_null<FunctionDecl>(getDecl());
   if (!FD)
     return false;
 
   return CheckerContext::isCLibraryFunction(FD, FunctionName);
 }
 
+AnalysisDeclContext *CallEvent::getCalleeAnalysisDeclContext() const {
+  const Decl *D = getDecl();
+
+  // If the callee is completely unknown, we cannot construct the stack frame.
+  if (!D)
+    return nullptr;
+
+  // FIXME: Skip virtual functions for now. There's no easy procedure to foresee
+  // the exact decl that should be used, especially when it's not a definition.
+  if (const Decl *RD = getRuntimeDefinition().getDecl())
+    if (RD != D)
+      return nullptr;
+
+  return LCtx->getAnalysisDeclContext()->getManager()->getContext(D);
+}
+
+const StackFrameContext *CallEvent::getCalleeStackFrame() const {
+  AnalysisDeclContext *ADC = getCalleeAnalysisDeclContext();
+  if (!ADC)
+    return nullptr;
+
+  const Expr *E = getOriginExpr();
+  if (!E)
+    return nullptr;
+
+  // Recover CFG block via reverse lookup.
+  // TODO: If we were to keep CFG element information as part of the CallEvent
+  // instead of doing this reverse lookup, we would be able to build the stack
+  // frame for non-expression-based calls, and also we wouldn't need the reverse
+  // lookup.
+  CFGStmtMap *Map = LCtx->getAnalysisDeclContext()->getCFGStmtMap();
+  const CFGBlock *B = Map->getBlock(E);
+  assert(B);
+
+  // Also recover CFG index by scanning the CFG block.
+  unsigned Idx = 0, Sz = B->size();
+  for (; Idx < Sz; ++Idx)
+    if (auto StmtElem = (*B)[Idx].getAs<CFGStmt>())
+      if (StmtElem->getStmt() == E)
+        break;
+  assert(Idx < Sz);
+
+  return ADC->getManager()->getStackFrame(ADC, LCtx, E, B, Idx);
+}
+
+const VarRegion *CallEvent::getParameterLocation(unsigned Index) const {
+  const StackFrameContext *SFC = getCalleeStackFrame();
+  // We cannot construct a VarRegion without a stack frame.
+  if (!SFC)
+    return nullptr;
+
+  const ParmVarDecl *PVD = parameters()[Index];
+  const VarRegion *VR =
+      State->getStateManager().getRegionManager().getVarRegion(PVD, SFC);
+
+  // This sanity check would fail if our parameter declaration doesn't
+  // correspond to the stack frame's function declaration.
+  assert(VR->getStackFrame() == SFC);
+
+  return VR;
+}
+
 /// Returns true if a type is a pointer-to-const or reference-to-const
 /// with no further indirection.
 static bool isPointerToConst(QualType Ty) {
   QualType PointeeTy = Ty->getPointeeType();
   if (PointeeTy == QualType())
     return false;
   if (!PointeeTy.isConstQualified())
     return false;