[Sema] Fix -Warray-bounds false negative when casting an out-of-bounds array item

Patch by Ilya Mirsky!

Fixes: http://llvm.org/PR44343

Reviewed By: rsmith

Differential Revision: https://reviews.llvm.org/D71714

1 files changed, 56 insertions, 55 deletions

diff --git a/clang/lib/Sema/SemaChecking.cpp b/clang/lib/Sema/SemaChecking.cpp
index 2d3d36f..17dd5c9 100644
--- a/clang/lib/Sema/SemaChecking.cpp
+++ b/clang/lib/Sema/SemaChecking.cpp
@@ -14387,62 +14387,63 @@ void Sema::CheckArrayAccess(const Expr *BaseExpr, const Expr *IndexExpr,
                         PDiag(diag::note_array_declared_here) << ND);
 }
 
-void Sema::CheckArrayAccess(const Expr *expr) {
-  int AllowOnePastEnd = 0;
-  while (expr) {
-    expr = expr->IgnoreParenImpCasts();
-    switch (expr->getStmtClass()) {
-      case Stmt::ArraySubscriptExprClass: {
-        const ArraySubscriptExpr *ASE = cast<ArraySubscriptExpr>(expr);
-        CheckArrayAccess(ASE->getBase(), ASE->getIdx(), ASE,
-                         AllowOnePastEnd > 0);
-        expr = ASE->getBase();
-        break;
-      }
-      case Stmt::MemberExprClass: {
-        expr = cast<MemberExpr>(expr)->getBase();
-        break;
-      }
-      case Stmt::OMPArraySectionExprClass: {
-        const OMPArraySectionExpr *ASE = cast<OMPArraySectionExpr>(expr);
-        if (ASE->getLowerBound())
-          CheckArrayAccess(ASE->getBase(), ASE->getLowerBound(),
-                           /*ASE=*/nullptr, AllowOnePastEnd > 0);
-        return;
-      }
-      case Stmt::UnaryOperatorClass: {
-        // Only unwrap the * and & unary operators
-        const UnaryOperator *UO = cast<UnaryOperator>(expr);
-        expr = UO->getSubExpr();
-        switch (UO->getOpcode()) {
-          case UO_AddrOf:
-            AllowOnePastEnd++;
-            break;
-          case UO_Deref:
-            AllowOnePastEnd--;
-            break;
-          default:
-            return;
-        }
-        break;
-      }
-      case Stmt::ConditionalOperatorClass: {
-        const ConditionalOperator *cond = cast<ConditionalOperator>(expr);
-        if (const Expr *lhs = cond->getLHS())
-          CheckArrayAccess(lhs);
-        if (const Expr *rhs = cond->getRHS())
-          CheckArrayAccess(rhs);
-        return;
-      }
-      case Stmt::CXXOperatorCallExprClass: {
-        const auto *OCE = cast<CXXOperatorCallExpr>(expr);
-        for (const auto *Arg : OCE->arguments())
-          CheckArrayAccess(Arg);
-        return;
-      }
-      default:
-        return;
+void Sema::CheckArrayAccess(const Expr *expr, int AllowOnePastEnd) {
+  if (!expr)
+    return;
+
+  expr = expr->IgnoreParenCasts();
+  switch (expr->getStmtClass()) {
+  case Stmt::ArraySubscriptExprClass: {
+    const ArraySubscriptExpr *ASE = cast<ArraySubscriptExpr>(expr);
+    CheckArrayAccess(ASE->getBase(), ASE->getIdx(), ASE, AllowOnePastEnd > 0);
+    CheckArrayAccess(ASE->getBase(), AllowOnePastEnd);
+    return;
+  }
+  case Stmt::MemberExprClass: {
+    expr = cast<MemberExpr>(expr)->getBase();
+    CheckArrayAccess(expr, /*AllowOnePastEnd=*/0);
+    return;
+  }
+  case Stmt::OMPArraySectionExprClass: {
+    const OMPArraySectionExpr *ASE = cast<OMPArraySectionExpr>(expr);
+    if (ASE->getLowerBound())
+      CheckArrayAccess(ASE->getBase(), ASE->getLowerBound(),
+                       /*ASE=*/nullptr, AllowOnePastEnd > 0);
+    return;
+  }
+  case Stmt::UnaryOperatorClass: {
+    // Only unwrap the * and & unary operators
+    const UnaryOperator *UO = cast<UnaryOperator>(expr);
+    expr = UO->getSubExpr();
+    switch (UO->getOpcode()) {
+    case UO_AddrOf:
+      AllowOnePastEnd++;
+      break;
+    case UO_Deref:
+      AllowOnePastEnd--;
+      break;
+    default:
+      return;
     }
+    CheckArrayAccess(expr, AllowOnePastEnd);
+    return;
+  }
+  case Stmt::ConditionalOperatorClass: {
+    const ConditionalOperator *cond = cast<ConditionalOperator>(expr);
+    if (const Expr *lhs = cond->getLHS())
+      CheckArrayAccess(lhs, AllowOnePastEnd);
+    if (const Expr *rhs = cond->getRHS())
+      CheckArrayAccess(rhs, AllowOnePastEnd);
+    return;
+  }
+  case Stmt::CXXOperatorCallExprClass: {
+    const auto *OCE = cast<CXXOperatorCallExpr>(expr);
+    for (const auto *Arg : OCE->arguments())
+      CheckArrayAccess(Arg);
+    return;
+  }
+  default:
+    return;
   }
 }