r322775 - [analyzer] NFC: Forbid array elements of void type.

[Artem Dergachev via cfe-commits]

Author: dergachev
Date: Wed Jan 17 14:40:36 2018
New Revision: 322775

URL: http://llvm.org/viewvc/llvm-project?rev=322775&view=rev
Log:
[analyzer] NFC: Forbid array elements of void type.

Represent the symbolic value for results of pointer arithmetic on void pointers
in a different way: instead of making void-typed element regions, make
char-typed element regions.

Add an assertion that ensures that no void-typed regions are ever constructed.

This is a refactoring of internals that should not immediately affect
the analyzer's (default) behavior.

Differential Revision: https://reviews.llvm.org/D40939

Modified:
    cfe/trunk/include/clang/StaticAnalyzer/Core/PathSensitive/MemRegion.h
    cfe/trunk/lib/StaticAnalyzer/Core/ExprEngine.cpp
    cfe/trunk/lib/StaticAnalyzer/Core/SimpleSValBuilder.cpp

Modified: cfe/trunk/include/clang/StaticAnalyzer/Core/PathSensitive/MemRegion.h
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/StaticAnalyzer/Core/PathSensitive/MemRegion.h?rev=322775&r1=322774&r2=322775&view=diff
==============================================================================
--- cfe/trunk/include/clang/StaticAnalyzer/Core/PathSensitive/MemRegion.h (original)
+++ cfe/trunk/include/clang/StaticAnalyzer/Core/PathSensitive/MemRegion.h Wed Jan 17 14:40:36 2018
@@ -962,7 +962,10 @@ class CXXThisRegion : public TypedValueR
   CXXThisRegion(const PointerType *thisPointerTy,
                 const StackArgumentsSpaceRegion *sReg)
       : TypedValueRegion(sReg, CXXThisRegionKind),
-        ThisPointerTy(thisPointerTy) {}
+        ThisPointerTy(thisPointerTy) {
+    assert(ThisPointerTy->getPointeeType()->getAsCXXRecordDecl() &&
+           "Invalid region type!");
+  }
 
   static void ProfileRegion(llvm::FoldingSetNodeID &ID,
                             const PointerType *PT,
@@ -1076,6 +1079,8 @@ class ElementRegion : public TypedValueR
     assert((!Idx.getAs<nonloc::ConcreteInt>() ||
             Idx.castAs<nonloc::ConcreteInt>().getValue().isSigned()) &&
            "The index must be signed");
+    assert(!elementType.isNull() && !elementType->isVoidType() &&
+           "Invalid region type!");
   }
 
   static void ProfileRegion(llvm::FoldingSetNodeID& ID, QualType elementType,

Modified: cfe/trunk/lib/StaticAnalyzer/Core/ExprEngine.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/StaticAnalyzer/Core/ExprEngine.cpp?rev=322775&r1=322774&r2=322775&view=diff
==============================================================================
--- cfe/trunk/lib/StaticAnalyzer/Core/ExprEngine.cpp (original)
+++ cfe/trunk/lib/StaticAnalyzer/Core/ExprEngine.cpp Wed Jan 17 14:40:36 2018
@@ -2209,9 +2209,17 @@ void ExprEngine::VisitArraySubscriptExpr
     ProgramStateRef state = Node->getState();
 
     if (IsGLValueLike) {
-      SVal V = state->getLValue(A->getType(),
-          state->getSVal(Idx, LCtx),
-          state->getSVal(Base, LCtx));
+      QualType T = A->getType();
+
+      // One of the forbidden LValue types! We still need to have sensible
+      // symbolic locations to represent this stuff. Note that arithmetic on
+      // void pointers is a GCC extension.
+      if (T->isVoidType())
+        T = getContext().CharTy;
+
+      SVal V = state->getLValue(T,
+                                state->getSVal(Idx, LCtx),
+                                state->getSVal(Base, LCtx));
       Bldr.generateNode(A, Node, state->BindExpr(A, LCtx, V), nullptr,
           ProgramPoint::PostLValueKind);
     } else if (IsVectorType) {

Modified: cfe/trunk/lib/StaticAnalyzer/Core/SimpleSValBuilder.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/StaticAnalyzer/Core/SimpleSValBuilder.cpp?rev=322775&r1=322774&r2=322775&view=diff
==============================================================================
--- cfe/trunk/lib/StaticAnalyzer/Core/SimpleSValBuilder.cpp (original)
+++ cfe/trunk/lib/StaticAnalyzer/Core/SimpleSValBuilder.cpp Wed Jan 17 14:40:36 2018
@@ -988,6 +988,12 @@ SVal SimpleSValBuilder::evalBinOpLN(Prog
         elementType = resultTy->getPointeeType();
     }
 
+    // Represent arithmetic on void pointers as arithmetic on char pointers.
+    // It is fine when a TypedValueRegion of char value type represents
+    // a void pointer. Note that arithmetic on void pointers is a GCC extension.
+    if (elementType->isVoidType())
+      elementType = getContext().CharTy;
+
     if (Optional<NonLoc> indexV = index.getAs<NonLoc>()) {
       return loc::MemRegionVal(MemMgr.getElementRegion(elementType, *indexV,
                                                        superR, getContext()));