Index: include/clang/Basic/DiagnosticGroups.td
===================================================================
--- include/clang/Basic/DiagnosticGroups.td
+++ include/clang/Basic/DiagnosticGroups.td
@@ -144,6 +144,7 @@
 def : DiagGroup<"discard-qual">;
 def DivZero : DiagGroup<"division-by-zero">;
 def : DiagGroup<"div-by-zero", [DivZero]>;
+def DivSizeofPtr : DiagGroup<"sizeof-pointer-div">;
 
 def DocumentationHTML : DiagGroup<"documentation-html">;
 def DocumentationUnknownCommand : DiagGroup<"documentation-unknown-command">;
@@ -789,6 +790,7 @@
     SelfMove,
     SizeofArrayArgument,
     SizeofArrayDecay,
+    DivSizeofPtr,
     StringPlusInt,
     Trigraphs,
     Uninitialized,
Index: include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- include/clang/Basic/DiagnosticSemaKinds.td
+++ include/clang/Basic/DiagnosticSemaKinds.td
@@ -3294,6 +3294,10 @@
   InGroup<TautologicalUndefinedCompare>;
 def note_reference_is_return_value : Note<"%0 returns a reference">;
 
+def warn_division_sizeof_ptr : Warning<
+  "'%0' will return the size of the pointer, not the array itself">,
+  InGroup<DivSizeofPtr>, DefaultIgnore;
+
 def note_function_warning_silence : Note<
     "prefix with the address-of operator to silence this warning">;
 def note_function_to_function_call : Note<
Index: lib/Sema/SemaExpr.cpp
===================================================================
--- lib/Sema/SemaExpr.cpp
+++ lib/Sema/SemaExpr.cpp
@@ -8726,6 +8726,37 @@
       << LHS.get()->getSourceRange() << RHS.get()->getSourceRange();
 }
 
+static void DiagnoseDivisionSizeofPointer(Sema &S, Expr *LHS, Expr *RHS,
+                                          SourceLocation Loc) {
+  UnaryExprOrTypeTraitExpr *LUE =
+      dyn_cast_or_null<UnaryExprOrTypeTraitExpr>(LHS);
+  UnaryExprOrTypeTraitExpr *RUE =
+      dyn_cast_or_null<UnaryExprOrTypeTraitExpr>(RHS);
+
+  if (!LUE || !RUE)
+    return;
+  if (LUE->getKind() != UETT_SizeOf || LUE->isArgumentType() ||
+      RUE->getKind() != UETT_SizeOf)
+    return;
+
+  QualType LHSTy;
+  QualType RHSTy;
+  LHSTy = LUE->getArgumentExpr()->IgnoreParens()->getType();
+
+  if (RUE->isArgumentType()) {
+    RHSTy = RUE->getArgumentType();
+  } else {
+    RHSTy = RUE->getArgumentExpr()->IgnoreParens()->getType();
+  }
+
+  if (!LHSTy->isPointerType() || RHSTy->isPointerType())
+    return;
+  if (LHSTy->getPointeeType() != RHSTy)
+    return;
+
+  S.Diag(Loc, diag::warn_division_sizeof_ptr) << LHS << LHS->getSourceRange();
+}
+
 static void DiagnoseBadDivideOrRemainderValues(Sema& S, ExprResult &LHS,
                                                ExprResult &RHS,
                                                SourceLocation Loc, bool IsDiv) {
@@ -8756,8 +8787,10 @@
 
   if (compType.isNull() || !compType->isArithmeticType())
     return InvalidOperands(Loc, LHS, RHS);
-  if (IsDiv)
+  if (IsDiv) {
     DiagnoseBadDivideOrRemainderValues(*this, LHS, RHS, Loc, IsDiv);
+    DiagnoseDivisionSizeofPointer(*this, LHS.get(), RHS.get(), Loc);
+  }
   return compType;
 }
 
@@ -16599,4 +16632,4 @@
 
   return new (Context)
       ObjCAvailabilityCheckExpr(Version, AtLoc, RParen, Context.BoolTy);
-}
+}
\ No newline at end of file
Index: test/Sema/div-sizeof-ptr.c
===================================================================
--- test/Sema/div-sizeof-ptr.c
+++ test/Sema/div-sizeof-ptr.c
@@ -0,0 +1,14 @@
+// RUN: %clang_cc1 %s -verify -Wsizeof-pointer-div -fsyntax-only
+
+void test(int *p, int **q) {
+    int a1 = sizeof(p) / sizeof(*p);      // expected-warning {{'sizeof (p)' will return the size of the pointer, not the array itself}}
+    int a2 = sizeof p / sizeof *p;        // expected-warning {{'sizeof p' will return the size of the pointer, not the array itself}}
+    int a3 = sizeof(*q) / sizeof(**q);    // expected-warning {{'sizeof (*q)' will return the size of the pointer, not the array itself}}
+    int a4 = sizeof(p) / sizeof(int);     // expected-warning {{'sizeof (p)' will return the size of the pointer, not the array itself}}
+    int a5 = sizeof(p) / sizeof(p[0]);    // expected-warning {{'sizeof (p)' will return the size of the pointer, not the array itself}}
+
+    int b1 = sizeof(int *) / sizeof(int);
+    int b2 = sizeof(p) / sizeof(p);
+    int b3 = sizeof(*q) / sizeof(q);
+    int b4 = sizeof(p) / sizeof(char);
+}