[PATCH] D40939: [analyzer] Avoid element regions of void type.

[Artem Dergachev via Phabricator via cfe-commits]

NoQ updated this revision to Diff 127548.
NoQ added a comment.

- Fix comments as suggested by Devin.
- Point out that arithmetic on void pointers is a GNU extension.


https://reviews.llvm.org/D40939

Files:
  include/clang/StaticAnalyzer/Core/PathSensitive/MemRegion.h
  lib/StaticAnalyzer/Core/ExprEngine.cpp
  lib/StaticAnalyzer/Core/SimpleSValBuilder.cpp


Index: lib/StaticAnalyzer/Core/SimpleSValBuilder.cpp
===================================================================
--- lib/StaticAnalyzer/Core/SimpleSValBuilder.cpp
+++ lib/StaticAnalyzer/Core/SimpleSValBuilder.cpp
@@ -988,6 +988,12 @@
         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()));
Index: lib/StaticAnalyzer/Core/ExprEngine.cpp
===================================================================
--- lib/StaticAnalyzer/Core/ExprEngine.cpp
+++ lib/StaticAnalyzer/Core/ExprEngine.cpp
@@ -2178,9 +2178,17 @@
     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) {
Index: include/clang/StaticAnalyzer/Core/PathSensitive/MemRegion.h
===================================================================
--- include/clang/StaticAnalyzer/Core/PathSensitive/MemRegion.h
+++ include/clang/StaticAnalyzer/Core/PathSensitive/MemRegion.h
@@ -961,7 +961,10 @@
   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,
@@ -1075,6 +1078,8 @@
     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,


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