[Sema] Improve a -Warray-bounds diagnostic

Fix a bug where we would compare array sizes with incompatible
element types, and look through explicit casts.

rdar://44800168

Differential revision: https://reviews.llvm.org/D57064

llvm-svn: 352239

1 files changed, 19 insertions, 5 deletions

diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index 3c6a7779560..8f3fd162740 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -5228,15 +5228,29 @@ Sema::CheckStaticArrayArgument(SourceLocation CallLoc,
     return;
 
   const ConstantArrayType *ArgCAT =
-    Context.getAsConstantArrayType(ArgExpr->IgnoreParenImpCasts()->getType());
+    Context.getAsConstantArrayType(ArgExpr->IgnoreParenCasts()->getType());
   if (!ArgCAT)
     return;
 
-  if (ArgCAT->getSize().ult(CAT->getSize())) {
+  if (getASTContext().hasSameUnqualifiedType(CAT->getElementType(),
+                                             ArgCAT->getElementType())) {
+    if (ArgCAT->getSize().ult(CAT->getSize())) {
+      Diag(CallLoc, diag::warn_static_array_too_small)
+          << ArgExpr->getSourceRange()
+          << (unsigned)ArgCAT->getSize().getZExtValue()
+          << (unsigned)CAT->getSize().getZExtValue() << 0;
+      DiagnoseCalleeStaticArrayParam(*this, Param);
+    }
+    return;
+  }
+
+  Optional<CharUnits> ArgSize =
+      getASTContext().getTypeSizeInCharsIfKnown(ArgCAT);
+  Optional<CharUnits> ParmSize = getASTContext().getTypeSizeInCharsIfKnown(CAT);
+  if (ArgSize && ParmSize && *ArgSize < *ParmSize) {
     Diag(CallLoc, diag::warn_static_array_too_small)
-      << ArgExpr->getSourceRange()
-      << (unsigned) ArgCAT->getSize().getZExtValue()
-      << (unsigned) CAT->getSize().getZExtValue();
+        << ArgExpr->getSourceRange() << (unsigned)ArgSize->getQuantity()
+        << (unsigned)ParmSize->getQuantity() << 1;
     DiagnoseCalleeStaticArrayParam(*this, Param);
   }
 }