Index: include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- include/clang/Basic/DiagnosticSemaKinds.td
+++ include/clang/Basic/DiagnosticSemaKinds.td
@@ -5382,6 +5382,9 @@
   "dereference of type %1 that was reinterpret_cast from type %0 has undefined "
   "behavior">,
   InGroup<UndefinedReinterpretCast>, DefaultIgnore;
+def warn_taking_address_of_packed_member : Warning<
+  "taking address of packed member %0 of class or structure %q1 may result in an unaligned pointer value">,
+  InGroup<DiagGroup<"address-of-packed-member">>;
 
 def err_objc_object_assignment : Error<
   "cannot assign to class object (%0 invalid)">;
Index: lib/Sema/SemaExpr.cpp
===================================================================
--- lib/Sema/SemaExpr.cpp
+++ lib/Sema/SemaExpr.cpp
@@ -10514,6 +10514,23 @@
     return QualType();
   }
 
+  // Taking the address of a data member/field of a packed
+  // struct may be a problem if the pointer value is dereferenced
+  MemberExpr *ME = dyn_cast<MemberExpr>(op);
+  while (ME && isa<FieldDecl>(ME->getMemberDecl())) {
+    QualType BaseType = ME->getBase()->getType();
+    if (ME->isArrow())
+      BaseType = BaseType->getPointeeType();
+    RecordDecl *RD = BaseType->getAs<RecordType>()->getDecl();
+    if (RD->hasAttr<PackedAttr>() ||
+        ME->getMemberDecl()->hasAttr<PackedAttr>()) {
+      Diag(OpLoc, diag::warn_taking_address_of_packed_member)
+          << ME->getMemberDecl() << RD;
+      break;
+    }
+    ME = dyn_cast<MemberExpr>(ME->getBase());
+  }
+
   return Context.getPointerType(op->getType());
 }
 
Index: test/Sema/address-packed.c
===================================================================
--- /dev/null
+++ test/Sema/address-packed.c
@@ -0,0 +1,201 @@
+// RUN: %clang_cc1 -fsyntax-only -verify %s
+// RUN: %clang_cc1 -xc++ -fsyntax-only -verify %s
+extern void f1(int *);
+extern void f2(char *);
+
+struct Ok {
+  char c;
+  int x;
+};
+
+struct __attribute__((packed)) Arguable {
+  char c;
+  int x;
+#ifdef __cplusplus
+  static void foo();
+#endif
+};
+
+union __attribute__((packed)) UnionArguable {
+  char c;
+  int x;
+#ifdef __cplusplus
+  static void foo();
+#endif
+};
+
+extern void f3(void());
+
+typedef struct Arguable ArguableT;
+
+#ifdef __cplusplus
+namespace Foo {
+struct __attribute__((packed)) Arguable {
+  char c;
+  int x;
+  static void foo();
+};
+}
+#endif
+
+void g0() {
+  {
+    struct Ok ok;
+    f1(&ok.x); // no-warning
+    f2(&ok.c); // no-warning
+  }
+  {
+    struct Arguable arguable;
+    f1(&arguable.x); // expected-warning {{packed member 'x' of class or structure 'Arguable'}}
+    f2(&arguable.c); // expected-warning {{packed member 'c' of class or structure 'Arguable'}}
+  }
+  {
+    union UnionArguable arguable;
+    f1(&arguable.x); // expected-warning {{packed member 'x' of class or structure 'UnionArguable'}}
+    f2(&arguable.c); // expected-warning {{packed member 'c' of class or structure 'UnionArguable'}}
+  }
+  {
+    ArguableT arguable;
+    f1(&arguable.x); // expected-warning {{packed member 'x' of class or structure }}
+    f2(&arguable.c); // expected-warning {{packed member 'c' of class or structure }}
+  }
+  {
+    struct Arguable *arguable;
+    f1(&(arguable->x)); // expected-warning {{packed member 'x' of class or structure 'Arguable'}}
+    f2(&(arguable->c)); // expected-warning {{packed member 'c' of class or structure 'Arguable'}}
+  }
+  {
+    ArguableT *arguable;
+    f1(&(arguable->x)); // expected-warning {{packed member 'x' of class or structure 'Arguable'}}
+    f2(&(arguable->c)); // expected-warning {{packed member 'c' of class or structure 'Arguable'}}
+  }
+
+#ifdef __cplusplus
+  {
+    Ok ok;
+    f1(&ok.x); // no-warning
+    f2(&ok.c); // no-warning
+  }
+  {
+    Arguable arguable;
+    f1(&arguable.x);   // expected-warning {{packed member 'x' of class or structure 'Arguable'}}
+    f2(&arguable.c);   // expected-warning {{packed member 'c' of class or structure 'Arguable'}}
+    f3(&arguable.foo); // no-warning
+  }
+  {
+    Foo::Arguable arguable;
+    f1(&arguable.x);   // expected-warning {{packed member 'x' of class or structure 'Foo::Arguable'}}
+    f2(&arguable.c);   // expected-warning {{packed member 'c' of class or structure 'Foo::Arguable'}}
+    f3(&arguable.foo); // no-warning
+  }
+  {
+    Arguable arguable1;
+    Arguable &arguable(arguable1);
+    f1(&arguable.x);   // expected-warning {{packed member 'x' of class or structure 'Arguable'}}
+    f2(&arguable.c);   // expected-warning {{packed member 'c' of class or structure 'Arguable'}}
+    f3(&arguable.foo); // no-warning
+  }
+  {
+    Arguable *arguable1;
+    Arguable *&arguable(arguable1);
+    f1(&arguable->x);   // expected-warning {{packed member 'x' of class or structure 'Arguable'}}
+    f2(&arguable->c);   // expected-warning {{packed member 'c' of class or structure 'Arguable'}}
+    f3(&arguable->foo); // no-warning
+  }
+#endif
+}
+
+struct S1 {
+  char c;
+  int i __attribute__((packed));
+};
+
+int *g1(struct S1 *s1) {
+  return &s1->i; // expected-warning {{packed member 'i' of class or structure 'S1'}}
+}
+
+struct S2_i {
+  int i;
+};
+struct __attribute__((packed)) S2 {
+  char c;
+  struct S2_i inner;
+};
+
+int *g2(struct S2 *s2) {
+  return &s2->inner.i; // expected-warning {{packed member 'inner' of class or structure 'S2'}}
+}
+
+struct S2_a {
+  char c;
+  struct S2_i inner __attribute__((packed));
+};
+
+int *g2_a(struct S2_a *s2_a) {
+  return &s2_a->inner.i; // expected-warning {{packed member 'inner' of class or structure 'S2_a'}}
+}
+
+struct __attribute__((packed)) S3 {
+  char c;
+  struct {
+    int i;
+  } inner;
+};
+
+int *g3(struct S3 *s3) {
+  return &s3->inner.i; // expected-warning {{packed member 'inner' of class or structure 'S3'}}
+}
+
+struct S4 {
+  char c;
+  struct __attribute__((packed)) {
+    int i;
+  } inner;
+};
+
+int *g4(struct S4 *s4) {
+  return &s4->inner.i; // expected-warning {{packed member 'i' of class or structure 'S4::(anonymous)'}}
+}
+
+struct S5 {
+  char c;
+  struct {
+    char c1;
+    int i __attribute__((packed));
+  } inner;
+};
+
+int *g5(struct S5 *s5) {
+  return &s5->inner.i; // expected-warning {{packed member 'i' of class or structure 'S5::(anonymous)'}}
+}
+
+#ifdef __cplusplus
+struct __attribute__((packed)) A
+{
+    char c;
+    int x;
+
+    int* f0()
+    {
+        return &this->x; // expected-warning {{packed member 'x' of class or structure 'A'}}
+    }
+
+    int* g0()
+    {
+        return &x; // expected-warning {{packed member 'x' of class or structure 'A'}}
+    }
+};
+
+struct B : A
+{
+    int* f1()
+    {
+        return &this->x; // expected-warning {{packed member 'x' of class or structure 'A'}}
+    }
+
+    int* g1()
+    {
+        return &x; // expected-warning {{packed member 'x' of class or structure 'A'}}
+    }
+};
+#endif