C/C++: Add -Waddress-of-packed-memberhjl/pr51628/master

When address of packed member of struct or union is taken, it may result
in an unaligned pointer value.  This patch adds -Waddress-of-packed-member
to warn it:

$ cat x.i
struct pair_t
{
  char c;
  int i;
} __attribute__ ((packed));

extern struct pair_t p;
int *addr = &p.i;
$ gcc -O2 -S x.i
x.i:8:13: warning: initialization of 'int *' from address of packed member of 'struct pair_t' may result in an unaligned pointer value [-Waddress-of-packed-member]
 int *addr = &p.i;
             ^
$

This warning is enabled by default.

gcc/c/

	PR c/51628
	* doc/invoke.texi: Document -Wno-address-of-packed-member.

gcc/c-family/

	PR c/51628
	* c-common.h (warn_for_address_of_packed_member): New.
	* c-warn.c (warn_for_address_of_packed_member): New function.
	* c.opt: Add -Wno-address-of-packed-member.

gcc/c/

	PR c/51628
	* c-typeck.c (convert_for_assignment): Call
	warn_for_address_of_packed_member.  Issue an warning if address
	of packed member is taken.

gcc/cp/

	PR c/51628
	* call.c (convert_for_arg_passing): Call
	warn_for_address_of_packed_member.  Issue an warning if address
	of packed member is taken.
	* typeck.c (convert_for_assignment): Likewise.

gcc/testsuite/

	PR c/51628
	* c-c++-common/pr51628-1.c: New tests.
	* c-c++-common/pr51628-10.c: Likewise.
	* c-c++-common/pr51628-2.c: Likewise.
	* c-c++-common/pr51628-3.c: Likewise.
	* c-c++-common/pr51628-4.c: Likewise.
	* c-c++-common/pr51628-5.c: Likewise.
	* c-c++-common/pr51628-6.c: Likewise.
	* c-c++-common/pr51628-7.c: Likewise.
	* c-c++-common/pr51628-8.c: Likewise.
	* c-c++-common/pr51628-9.c: Likewise.
	* gcc.dg/pr51628-10.c: Likewise.
	* gcc.dg/pr51628-11.c: Likewise.
	* c-c++-common/ubsan/align-10.c: Add -Wno-address-of-packed-member.
	* c-c++-common/ubsan/align-2.c: Likewise.
	* c-c++-common/ubsan/align-4.c: Likewise.
	* c-c++-common/ubsan/align-6.c: Likewise.
	* c-c++-common/ubsan/align-7.c: Likewise.
	* c-c++-common/ubsan/align-8.c: Likewise.
	* g++.dg/ubsan/align-2.C: Likewise.
	* gcc.target/i386/avx512bw-vmovdqu16-2.c: Likewise.
	* gcc.target/i386/avx512f-vmovdqu32-2.c: Likewise.
	* gcc.target/i386/avx512f-vmovdqu64-2.c: Likewise.
	* gcc.target/i386/avx512vl-vmovdqu16-2.c: Likewise.
	* gcc.target/i386/avx512vl-vmovdqu32-2.c: Likewise.
	* gcc.target/i386/avx512vl-vmovdqu64-2.c: Likewise.

32 files changed, 543 insertions, 16 deletions

diff --git a/gcc/c-family/c-common.h b/gcc/c-family/c-common.h
index d090881e95d..ef31e4d0aa2 100644
--- a/gcc/c-family/c-common.h
+++ b/gcc/c-family/c-common.h
@@ -1384,6 +1384,7 @@ extern void c_do_switch_warnings (splay_tree, location_t, tree, tree, bool,
 				  bool);
 extern void warn_for_omitted_condop (location_t, tree);
 extern void warn_for_restrict (unsigned, tree *, unsigned);
+extern tree warn_for_address_of_packed_member (tree type, tree rhs);
 
 /* Places where an lvalue, or modifiable lvalue, may be required.
    Used to select diagnostic messages in lvalue_error and
diff --git a/gcc/c-family/c-warn.c b/gcc/c-family/c-warn.c
index 7d87c455ec0..c755df13ca1 100644
--- a/gcc/c-family/c-warn.c
+++ b/gcc/c-family/c-warn.c
@@ -2576,3 +2576,59 @@ warn_for_multistatement_macros (location_t body_loc, location_t next_loc,
     inform (guard_loc, "some parts of macro expansion are not guarded by "
 	    "this %qs clause", guard_tinfo_to_string (keyword));
 }
+
+/* Return struct or union type if the right hand type, RHS, is the
+   address of packed member of struct or union when assigning to TYPE.
+   Otherwise, return NULL_TREE.  */
+
+tree
+warn_for_address_of_packed_member (tree type, tree rhs)
+{
+  if (!warn_address_of_packed_member || !POINTER_TYPE_P (type))
+    return NULL_TREE;
+
+  if (TREE_CODE (rhs) == NOP_EXPR)
+    rhs = TREE_OPERAND (rhs, 0);
+
+  tree base;
+  tree field = NULL_TREE;
+  tree rhs_type;
+
+  switch (TREE_CODE (rhs))
+    {
+    case ADDR_EXPR:
+      base = TREE_OPERAND (rhs, 0);
+      while (TREE_CODE (base) == ARRAY_REF)
+	base = TREE_OPERAND (base, 0);
+      if (TREE_CODE (base) != COMPONENT_REF)
+	return NULL_TREE;
+      field = TREE_OPERAND (base, 1);
+      break;
+    case COMPONENT_REF:
+      rhs_type = TREE_TYPE (rhs);
+      if (TREE_CODE (rhs_type) != ARRAY_TYPE
+	  || (TYPE_MAIN_VARIANT (TREE_TYPE (type))
+	      != TYPE_MAIN_VARIANT (TREE_TYPE (rhs_type))))
+	return NULL_TREE;
+      field = TREE_OPERAND (rhs, 1);
+      break;
+    default:
+      return NULL_TREE;
+    }
+
+  if (TREE_CODE (field) == FIELD_DECL && DECL_PACKED (field))
+    {
+      /* Check the expected alignment against the field alignment.  */
+      unsigned int type_align = TYPE_ALIGN (TREE_TYPE (type));
+      tree context = DECL_CONTEXT (field);
+      unsigned int record_align = TYPE_ALIGN (context);
+      if ((record_align % type_align) != 0)
+	return context;
+      tree field_off = byte_position (field);
+      if (!multiple_of_p (TREE_TYPE (field_off), field_off,
+			  size_int (type_align / BITS_PER_UNIT)))
+	return context;
+    }
+
+  return NULL_TREE;
+}
diff --git a/gcc/c-family/c.opt b/gcc/c-family/c.opt
index 16a515afd55..686d52a2055 100644
--- a/gcc/c-family/c.opt
+++ b/gcc/c-family/c.opt
@@ -599,6 +599,10 @@ Wincompatible-pointer-types
 C ObjC Var(warn_incompatible_pointer_types) Init(1) Warning
 Warn when there is a conversion between pointers that have incompatible types.
 
+Waddress-of-packed-member
+C ObjC C++ ObjC++ Var(warn_address_of_packed_member) Init(1) Warning
+Warn when the address of packed member of struct or union is taken.
+
 Winit-self
 C ObjC C++ ObjC++ Var(warn_init_self) Warning LangEnabledBy(C++ ObjC++,Wall)
 Warn about variables which are initialized to themselves.
diff --git a/gcc/c/c-typeck.c b/gcc/c/c-typeck.c
index e22bc740bca..8e31d6cc5fd 100644
--- a/gcc/c/c-typeck.c
+++ b/gcc/c/c-typeck.c
@@ -6495,7 +6495,45 @@ convert_for_assignment (location_t location, location_t expr_loc, tree type,
     }
 
   if (TYPE_MAIN_VARIANT (type) == TYPE_MAIN_VARIANT (rhstype))
-    return rhs;
+    {
+      tree context = warn_for_address_of_packed_member (type, orig_rhs);
+      if (context)
+	switch (errtype)
+	  {
+	  case ic_argpass:
+	    warning_at (expr_loc, OPT_Waddress_of_packed_member,
+			"passing argument %d %qT of %qE from address "
+			"of packed member of %qT may result in an "
+			"unaligned pointer value",
+			parmnum, type, rname, context);
+	    break;
+	  case ic_assign:
+	    warning_at (location, OPT_Waddress_of_packed_member,
+			"assignment to %qT from address of packed "
+			"member of %qT may result in an unaligned "
+			"pointer value",
+			type, context);
+	    break;
+	  case ic_init:
+	    warning_at (location, OPT_Waddress_of_packed_member,
+			"initialization of %qT from address of packed "
+			"member of %qT may result in an unaligned "
+			"pointer value",
+			type, context);
+	    break;
+	  case ic_return:
+	    warning_at (location, OPT_Waddress_of_packed_member,
+			"returning address of packed member of %qT "
+			"from a function with return type %qT may "
+			"result in an unaligned pointer value",
+			context, type);
+	    break;
+	  default:
+	    gcc_unreachable ();
+	  }
+
+      return rhs;
+    }
 
   if (coder == VOID_TYPE)
     {
diff --git a/gcc/cp/call.c b/gcc/cp/call.c
index f5542850cea..8672ab0d58c 100644
--- a/gcc/cp/call.c
+++ b/gcc/cp/call.c
@@ -7416,6 +7416,14 @@ convert_for_arg_passing (tree type, tree val, tsubst_flags_t complain)
 	}
       maybe_warn_parm_abi (type, EXPR_LOC_OR_LOC (val, input_location));
     }
+
+  tree context = warn_for_address_of_packed_member (type, val);
+  if (context)
+    warning (OPT_Waddress_of_packed_member,
+	     "passing argument of type %qT from address of member of "
+	     "packed %qT may result in an unaligned pointer value",
+	     type, context);
+
   return val;
 }
 
diff --git a/gcc/cp/typeck.c b/gcc/cp/typeck.c
index d0adb798278..78ed0d61f8b 100644
--- a/gcc/cp/typeck.c
+++ b/gcc/cp/typeck.c
@@ -8887,6 +8887,47 @@ convert_for_assignment (tree type, tree rhs,
       TREE_NO_WARNING (rhs) = 1;
     }
 
+  tree context = warn_for_address_of_packed_member (type, rhs);
+  if (context)
+    switch (errtype)
+      {
+      case ICR_ARGPASS:
+      case ICR_DEFAULT_ARGUMENT:
+	warning (OPT_Waddress_of_packed_member,
+		 "passing argument %d %qT of %qD from address of "
+		 "packed member of %qT may result in an unaligned "
+		 "pointer value",
+		 parmnum, type, fndecl, context);
+	break;
+      case ICR_CONVERTING:
+	warning (OPT_Waddress_of_packed_member,
+		 "converting to %qT from address of packed member of "
+		 "%qT may result in an unaligned pointer value",
+		 type, context);
+	break;
+      case ICR_ASSIGN:
+	warning (OPT_Waddress_of_packed_member,
+		 "assignment to %qT from address of packed member of "
+		 "%qT may result in an unaligned pointer value",
+		 type, context);
+	break;
+      case ICR_INIT:
+	warning (OPT_Waddress_of_packed_member,
+		 "initialization of %qT from address of packed member "
+		 "of %qT may result in an unaligned pointer value",
+		 type, context);
+	break;
+      case ICR_RETURN:
+	warning (OPT_Waddress_of_packed_member,
+		 "returning address of packed member of %qT from a "
+		 "function with return type %qT may result in an "
+		 "unaligned pointer value",
+		 context, type);
+	break;
+      default:
+	gcc_unreachable ();
+      }
+
   return perform_implicit_conversion_flags (strip_top_quals (type), rhs,
 					    complain, flags);
 }
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 98b73db17af..b83d113b76d 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -259,8 +259,8 @@ Objective-C and Objective-C++ Dialects}.
 @xref{Warning Options,,Options to Request or Suppress Warnings}.
 @gccoptlist{-fsyntax-only  -fmax-errors=@var{n}  -Wpedantic @gol
 -pedantic-errors @gol
--w  -Wextra  -Wall  -Waddress  -Waggregate-return  @gol
--Walloc-zero  -Walloc-size-larger-than=@var{n}
+-w  -Wextra  -Wall  -Waddress -Waddress-of-packed-member @gol
+-Waggregate-return -Walloc-zero -Walloc-size-larger-than=@var{n} @gol
 -Walloca  -Walloca-larger-than=@var{n} @gol
 -Wno-aggressive-loop-optimizations  -Warray-bounds  -Warray-bounds=@var{n} @gol
 -Wno-attributes  -Wbool-compare  -Wbool-operation @gol
@@ -6379,6 +6379,13 @@ behavior and are not portable in C, so they usually indicate that the
 programmer intended to use @code{strcmp}.  This warning is enabled by
 @option{-Wall}.
 
+@item -Waddress-of-packed-member
+@opindex Waddress-of-packed-member
+@opindex Wno-address-of-packed-member
+Warn when the address of packed member of struct or union is taken,
+which usually results in an unaligned pointer value.  This is
+enabled by default.
+
 @item -Wlogical-op
 @opindex Wlogical-op
 @opindex Wno-logical-op
diff --git a/gcc/testsuite/c-c++-common/pr51628-1.c b/gcc/testsuite/c-c++-common/pr51628-1.c
new file mode 100644
index 00000000000..5324f9cc964
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/pr51628-1.c
@@ -0,0 +1,29 @@
+/* PR c/51628.  */
+/* { dg-do compile } */
+/* { dg-options "-O" } */
+
+struct pair_t
+{
+  int x;
+  int i;
+} __attribute__((packed, aligned (4)));
+
+extern struct pair_t p;
+extern int *x;
+extern void bar (int *);
+
+int *addr = &p.i;
+
+int *
+foo (void)
+{
+  struct pair_t arr[2] = { { 1, 10 }, { 2, 20 } };
+  int *p0, *p1;
+  p0 = &arr[0].i;
+  bar (p0);
+  p1 = &arr[1].i;
+  bar (p1);
+  bar (&p.i);
+  x = &p.i;
+  return &p.i;
+}
diff --git a/gcc/testsuite/c-c++-common/pr51628-10.c b/gcc/testsuite/c-c++-common/pr51628-10.c
new file mode 100644
index 00000000000..085fe1608c4
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/pr51628-10.c
@@ -0,0 +1,24 @@
+/* PR c/51628.  */
+/* { dg-do run { target int128 } } */
+/* { dg-options "-O2" } */
+
+struct pair_t
+{
+  char c;
+  __int128_t i;
+} __attribute__ ((packed));
+
+typedef struct unaligned_int128_t_
+{
+  __int128_t value;
+} __attribute__((packed)) unaligned_int128_t;
+
+struct pair_t p = {0, 1};
+unaligned_int128_t *addr = (unaligned_int128_t *) &p.i;
+
+int 
+main() 
+{
+  addr->value = ~(__int128_t)0;
+  return (p.i != 1) ? 0 : 1;
+}
diff --git a/gcc/testsuite/c-c++-common/pr51628-2.c b/gcc/testsuite/c-c++-common/pr51628-2.c
new file mode 100644
index 00000000000..abfb84ddd05
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/pr51628-2.c
@@ -0,0 +1,29 @@
+/* PR c/51628.  */
+/* { dg-do compile } */
+/* { dg-options "-O" } */
+
+struct pair_t
+{
+  int x;
+  int i;
+} __attribute__((packed, aligned (8)));
+
+extern struct pair_t p;
+extern int *x;
+extern void bar (int *);
+
+int *addr = &p.i;
+
+int *
+foo (void)
+{
+  struct pair_t arr[2] = { { 1, 10 }, { 2, 20 } };
+  int *p0, *p1;
+  p0 = &arr[0].i;
+  bar (p0);
+  p1 = &arr[1].i;
+  bar (p1);
+  bar (&p.i);
+  x = &p.i;
+  return &p.i;
+}
diff --git a/gcc/testsuite/c-c++-common/pr51628-3.c b/gcc/testsuite/c-c++-common/pr51628-3.c
new file mode 100644
index 00000000000..0ea94c845a0
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/pr51628-3.c
@@ -0,0 +1,35 @@
+/* PR c/51628.  */
+/* { dg-do compile } */
+/* { dg-options "-O" } */
+
+struct pair_t
+{
+  int x;
+  int i;
+} __attribute__((packed, aligned (2)));
+
+extern struct pair_t p;
+extern int *x;
+extern void bar (int *);
+
+int *addr = &p.i;
+/* { dg-warning "may result in an unaligned pointer value" "" { target *-*-* } .-1 } */
+
+int *
+foo (void)
+{
+  struct pair_t arr[2] = { { 1, 10 }, { 2, 20 } };
+  int *p0, *p1;
+  p0 = &arr[0].i;
+/* { dg-warning "may result in an unaligned pointer value" "" { target *-*-* } .-1 } */
+  bar (p0);
+  p1 = &arr[1].i;
+/* { dg-warning "may result in an unaligned pointer value" "" { target *-*-* } .-1 } */
+  bar (p1);
+  bar (&p.i);
+/* { dg-warning "may result in an unaligned pointer value" "" { target *-*-* } .-1 } */
+  x = &p.i;
+/* { dg-warning "may result in an unaligned pointer value" "" { target *-*-* } .-1 } */
+  return &p.i;
+/* { dg-warning "may result in an unaligned pointer value" "" { target *-*-* } .-1 } */
+}
diff --git a/gcc/testsuite/c-c++-common/pr51628-4.c b/gcc/testsuite/c-c++-common/pr51628-4.c
new file mode 100644
index 00000000000..c4c1fb72d6d
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/pr51628-4.c
@@ -0,0 +1,35 @@
+/* PR c/51628.  */
+/* { dg-do compile } */
+/* { dg-options "-O" } */
+
+struct pair_t
+{
+  int x;
+  int i;
+} __attribute__((packed));
+
+extern struct pair_t p;
+extern int *x;
+extern void bar (int *);
+
+int *addr = &p.i;
+/* { dg-warning "may result in an unaligned pointer value" "" { target *-*-* } .-1 } */
+
+int *
+foo (void)
+{
+  struct pair_t arr[2] = { { 1, 10 }, { 2, 20 } };
+  int *p0, *p1;
+  p0 = &arr[0].i;
+/* { dg-warning "may result in an unaligned pointer value" "" { target *-*-* } .-1 } */
+  bar (p0);
+  p1 = &arr[1].i;
+/* { dg-warning "may result in an unaligned pointer value" "" { target *-*-* } .-1 } */
+  bar (p1);
+  bar (&p.i);
+/* { dg-warning "may result in an unaligned pointer value" "" { target *-*-* } .-1 } */
+  x = &p.i;
+/* { dg-warning "may result in an unaligned pointer value" "" { target *-*-* } .-1 } */
+  return &p.i;
+/* { dg-warning "may result in an unaligned pointer value" "" { target *-*-* } .-1 } */
+}
diff --git a/gcc/testsuite/c-c++-common/pr51628-5.c b/gcc/testsuite/c-c++-common/pr51628-5.c
new file mode 100644
index 00000000000..9d7c309a0ef
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/pr51628-5.c
@@ -0,0 +1,35 @@
+/* PR c/51628.  */
+/* { dg-do compile } */
+/* { dg-options "-O" } */
+
+struct pair_t
+{
+  char x;
+  int i;
+} __attribute__((packed));
+
+extern struct pair_t p;
+extern int *x;
+extern void bar (int *);
+
+int *addr = &p.i;
+/* { dg-warning "may result in an unaligned pointer value" "" { target *-*-* } .-1 } */
+
+int *
+foo (void)
+{
+  struct pair_t arr[2] = { { 1, 10 }, { 2, 20 } };
+  int *p0, *p1;
+  p0 = &arr[0].i;
+/* { dg-warning "may result in an unaligned pointer value" "" { target *-*-* } .-1 } */
+  bar (p0);
+  p1 = &arr[1].i;
+/* { dg-warning "may result in an unaligned pointer value" "" { target *-*-* } .-1 } */
+  bar (p1);
+  bar (&p.i);
+/* { dg-warning "may result in an unaligned pointer value" "" { target *-*-* } .-1 } */
+  x = &p.i;
+/* { dg-warning "may result in an unaligned pointer value" "" { target *-*-* } .-1 } */
+  return &p.i;
+/* { dg-warning "may result in an unaligned pointer value" "" { target *-*-* } .-1 } */
+}
diff --git a/gcc/testsuite/c-c++-common/pr51628-6.c b/gcc/testsuite/c-c++-common/pr51628-6.c
new file mode 100644
index 00000000000..52aa07a4cf3
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/pr51628-6.c
@@ -0,0 +1,35 @@
+/* PR c/51628.  */
+/* { dg-do compile } */
+/* { dg-options "-O" } */
+
+struct pair_t
+{
+  char x;
+  int i;
+} __attribute__((packed, aligned (4)));
+
+extern struct pair_t p;
+extern int *x;
+extern void bar (int *);
+
+int *addr = &p.i;
+/* { dg-warning "may result in an unaligned pointer value" "" { target *-*-* } .-1 } */
+
+int *
+foo (void)
+{
+  struct pair_t arr[2] = { { 1, 10 }, { 2, 20 } };
+  int *p0, *p1;
+  p0 = &arr[0].i;
+/* { dg-warning "may result in an unaligned pointer value" "" { target *-*-* } .-1 } */
+  bar (p0);
+  p1 = &arr[1].i;
+/* { dg-warning "may result in an unaligned pointer value" "" { target *-*-* } .-1 } */
+  bar (p1);
+  bar (&p.i);
+/* { dg-warning "may result in an unaligned pointer value" "" { target *-*-* } .-1 } */
+  x = &p.i;
+/* { dg-warning "may result in an unaligned pointer value" "" { target *-*-* } .-1 } */
+  return &p.i;
+/* { dg-warning "may result in an unaligned pointer value" "" { target *-*-* } .-1 } */
+}
diff --git a/gcc/testsuite/c-c++-common/pr51628-7.c b/gcc/testsuite/c-c++-common/pr51628-7.c
new file mode 100644
index 00000000000..ae4a681f966
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/pr51628-7.c
@@ -0,0 +1,29 @@
+/* PR c/51628.  */
+/* { dg-do compile } */
+/* { dg-options "-O" } */
+
+struct pair_t
+{
+  int x;
+  int i[4];
+} __attribute__((packed, aligned (4)));
+
+extern struct pair_t p;
+extern int *x;
+extern void bar (int *);
+
+int *addr = p.i;
+
+int *
+foo (struct pair_t *p)
+{
+  int *p0, *p1;
+  p0 = p->i;
+  bar (p0);
+  p1 = &p->i[1];
+  bar (p1);
+  bar (p->i);
+  bar (&p->i[2]);
+  x = p->i;
+  return &p->i[3];
+}
diff --git a/gcc/testsuite/c-c++-common/pr51628-8.c b/gcc/testsuite/c-c++-common/pr51628-8.c
new file mode 100644
index 00000000000..cc2dae096ae
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/pr51628-8.c
@@ -0,0 +1,36 @@
+/* PR c/51628.  */
+/* { dg-do compile } */
+/* { dg-options "-O" } */
+
+struct pair_t
+{
+  char x;
+  int i[4];
+} __attribute__ ((packed, aligned (4)));
+
+extern struct pair_t p;
+extern int *x;
+extern void bar (int *);
+
+int *addr = p.i;
+/* { dg-warning "may result in an unaligned pointer value" "" { target *-*-* } .-1 } */
+
+int *
+foo (struct pair_t *p)
+{
+  int *p0, *p1;
+  p0 = p->i;
+/* { dg-warning "may result in an unaligned pointer value" "" { target *-*-* } .-1 } */
+  bar (p0);
+  p1 = &p->i[1];
+/* { dg-warning "may result in an unaligned pointer value" "" { target *-*-* } .-1 } */
+  bar (p1);
+  bar (p->i);
+/* { dg-warning "may result in an unaligned pointer value" "" { target *-*-* } .-1 } */
+  bar (&p->i[2]);
+/* { dg-warning "may result in an unaligned pointer value" "" { target *-*-* } .-1 } */
+  x = p->i;
+/* { dg-warning "may result in an unaligned pointer value" "" { target *-*-* } .-1 } */
+  return &p->i[3];
+/* { dg-warning "may result in an unaligned pointer value" "" { target *-*-* } .-1 } */
+}
diff --git a/gcc/testsuite/c-c++-common/pr51628-9.c b/gcc/testsuite/c-c++-common/pr51628-9.c
new file mode 100644
index 00000000000..0470aa3b93d
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/pr51628-9.c
@@ -0,0 +1,36 @@
+/* PR c/51628.  */
+/* { dg-do compile } */
+/* { dg-options "-O" } */
+
+struct pair_t
+{
+  int x;
+  int i[4];
+} __attribute__ ((packed));
+
+extern struct pair_t p;
+extern int *x;
+extern void bar (int *);
+
+int *addr = p.i;
+/* { dg-warning "may result in an unaligned pointer value" "" { target *-*-* } .-1 } */
+
+int *
+foo (struct pair_t *p)
+{
+  int *p0, *p1;
+  p0 = p->i;
+/* { dg-warning "may result in an unaligned pointer value" "" { target *-*-* } .-1 } */
+  bar (p0);
+  p1 = &p->i[1];
+/* { dg-warning "may result in an unaligned pointer value" "" { target *-*-* } .-1 } */
+  bar (p1);
+  bar (p->i);
+/* { dg-warning "may result in an unaligned pointer value" "" { target *-*-* } .-1 } */
+  bar (&p->i[2]);
+/* { dg-warning "may result in an unaligned pointer value" "" { target *-*-* } .-1 } */
+  x = p->i;
+/* { dg-warning "may result in an unaligned pointer value" "" { target *-*-* } .-1 } */
+  return &p->i[3];
+/* { dg-warning "may result in an unaligned pointer value" "" { target *-*-* } .-1 } */
+}
diff --git a/gcc/testsuite/c-c++-common/ubsan/align-10.c b/gcc/testsuite/c-c++-common/ubsan/align-10.c
index 56ae9ebfe30..6210533173c 100644
--- a/gcc/testsuite/c-c++-common/ubsan/align-10.c
+++ b/gcc/testsuite/c-c++-common/ubsan/align-10.c
@@ -1,6 +1,6 @@
 /* Limit this to known non-strict alignment targets.  */
 /* { dg-do run { target { i?86-*-linux* x86_64-*-linux* } } } */
-/* { dg-options "-O -fsanitize=alignment -fsanitize-recover=alignment" } */
+/* { dg-options "-O -fsanitize=alignment -fsanitize-recover=alignment -Wno-address-of-packed-member" } */
 
 struct R { int a; } r;
 struct S { struct R a; char b; long long c; short d[10]; };
diff --git a/gcc/testsuite/c-c++-common/ubsan/align-2.c b/gcc/testsuite/c-c++-common/ubsan/align-2.c
index 071de8c202a..336b1c3c907 100644
--- a/gcc/testsuite/c-c++-common/ubsan/align-2.c
+++ b/gcc/testsuite/c-c++-common/ubsan/align-2.c
@@ -1,6 +1,6 @@
 /* Limit this to known non-strict alignment targets.  */
 /* { dg-do run { target { i?86-*-linux* x86_64-*-linux* } } } */
-/* { dg-options "-fsanitize=alignment" } */
+/* { dg-options "-fsanitize=alignment -Wno-address-of-packed-member" } */
 
 struct S { int a; char b; long long c; short d[10]; };
 struct T { char a; long long b; };
diff --git a/gcc/testsuite/c-c++-common/ubsan/align-4.c b/gcc/testsuite/c-c++-common/ubsan/align-4.c
index 3252595d330..d5feeee29c6 100644
--- a/gcc/testsuite/c-c++-common/ubsan/align-4.c
+++ b/gcc/testsuite/c-c++-common/ubsan/align-4.c
@@ -1,6 +1,6 @@
 /* Limit this to known non-strict alignment targets.  */
 /* { dg-do run { target { i?86-*-linux* x86_64-*-linux* } } } */
-/* { dg-options "-fsanitize=null,alignment" } */
+/* { dg-options "-fsanitize=null,alignment -Wno-address-of-packed-member" } */
 
 #include "align-2.c"
 
diff --git a/gcc/testsuite/c-c++-common/ubsan/align-6.c b/gcc/testsuite/c-c++-common/ubsan/align-6.c
index 3364746fb27..0302b7b8894 100644
--- a/gcc/testsuite/c-c++-common/ubsan/align-6.c
+++ b/gcc/testsuite/c-c++-common/ubsan/align-6.c
@@ -1,6 +1,6 @@
 /* Limit this to known non-strict alignment targets.  */
 /* { dg-do run { target { i?86-*-linux* x86_64-*-linux* } } } */
-/* { dg-options "-O -fsanitize=alignment -fsanitize-recover=alignment" } */
+/* { dg-options "-O -fsanitize=alignment -fsanitize-recover=alignment -Wno-address-of-packed-member" } */
 
 struct S { int a; char b; long long c; short d[10]; };
 struct T { char a; long long b; };
diff --git a/gcc/testsuite/c-c++-common/ubsan/align-7.c b/gcc/testsuite/c-c++-common/ubsan/align-7.c
index ec4e87f56d5..dd1e8c91cef 100644
--- a/gcc/testsuite/c-c++-common/ubsan/align-7.c
+++ b/gcc/testsuite/c-c++-common/ubsan/align-7.c
@@ -1,6 +1,6 @@
 /* Limit this to known non-strict alignment targets.  */
 /* { dg-do run { target { i?86-*-linux* x86_64-*-linux* } } } */
-/* { dg-options "-O -fsanitize=alignment -fno-sanitize-recover=alignment -fdump-tree-sanopt-details" } */
+/* { dg-options "-O -fsanitize=alignment -fno-sanitize-recover=alignment -Wno-address-of-packed-member -fdump-tree-sanopt-details" } */
 /* { dg-skip-if "" { *-*-* } { "-flto -fno-fat-lto-objects" } } */
 /* { dg-shouldfail "ubsan" } */
 
diff --git a/gcc/testsuite/c-c++-common/ubsan/align-8.c b/gcc/testsuite/c-c++-common/ubsan/align-8.c
index 61c1ceb6682..5fe0e0fe931 100644
--- a/gcc/testsuite/c-c++-common/ubsan/align-8.c
+++ b/gcc/testsuite/c-c++-common/ubsan/align-8.c
@@ -1,6 +1,6 @@
 /* Limit this to known non-strict alignment targets.  */
 /* { dg-do run { target { i?86-*-linux* x86_64-*-linux* } } } */
-/* { dg-options "-O -fsanitize=alignment -fsanitize-undefined-trap-on-error -fdump-tree-sanopt-details" } */
+/* { dg-options "-O -fsanitize=alignment -fsanitize-undefined-trap-on-error -Wno-address-of-packed-member -fdump-tree-sanopt-details" } */
 /* { dg-skip-if "" { *-*-* } { "-flto -fno-fat-lto-objects" } } */
 /* { dg-shouldfail "ubsan" } */
 
diff --git a/gcc/testsuite/g++.dg/ubsan/align-2.C b/gcc/testsuite/g++.dg/ubsan/align-2.C
index 3e4f5485d02..c97ede88392 100644
--- a/gcc/testsuite/g++.dg/ubsan/align-2.C
+++ b/gcc/testsuite/g++.dg/ubsan/align-2.C
@@ -1,6 +1,6 @@
 // Limit this to known non-strict alignment targets.
 // { dg-do run { target { i?86-*-linux* x86_64-*-linux* } } }
-// { dg-options "-fsanitize=alignment -Wall -Wno-unused-variable -std=c++11" }
+// { dg-options "-fsanitize=alignment -Wall -Wno-unused-variable -Wno-address-of-packed-member -std=c++11" }
 
 typedef const long int L;
 struct S { long int l; char buf[1 + sizeof (int) + sizeof (L)]; } s;
diff --git a/gcc/testsuite/gcc.dg/pr51628-10.c b/gcc/testsuite/gcc.dg/pr51628-10.c
new file mode 100644
index 00000000000..03a04eff75c
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr51628-10.c
@@ -0,0 +1,23 @@
+/* PR c/51628.  */
+/* { dg-do compile } */
+/* { dg-options "-O" } */
+
+void foo (int *);
+
+int *
+bar (int n, int k, void *ptr)
+{
+  struct A
+  {
+    int c[k];
+    int x[n];
+  } __attribute__ ((packed, aligned (4)));
+  struct A *p = (struct A *) ptr;
+
+  int *p0, *p1;
+  p0 = p->x;
+  foo (p0);
+  p1 = &p->x[1];
+  foo (p1);
+  return &p->x[1];
+}
diff --git a/gcc/testsuite/gcc.dg/pr51628-11.c b/gcc/testsuite/gcc.dg/pr51628-11.c
new file mode 100644
index 00000000000..7ff03e85cea
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr51628-11.c
@@ -0,0 +1,26 @@
+/* PR c/51628.  */
+/* { dg-do compile } */
+/* { dg-options "-O" } */
+
+void foo (int *);
+
+int *
+bar (int n, int k, void *ptr)
+{
+  struct A
+  {
+    char c[k];
+    int x[n];
+  } __attribute__ ((packed));
+  struct A *p = (struct A *) ptr;
+
+  int *p0, *p1;
+  p0 = p->x;
+/* { dg-warning "may result in an unaligned pointer value" "" { target *-*-* } .-1 } */
+  foo (p0);
+  p1 = &p->x[1];
+/* { dg-warning "may result in an unaligned pointer value" "" { target *-*-* } .-1 } */
+  foo (p1);
+  return &p->x[1];
+/* { dg-warning "may result in an unaligned pointer value" "" { target *-*-* } .-1 } */
+}
diff --git a/gcc/testsuite/gcc.target/i386/avx512bw-vmovdqu16-2.c b/gcc/testsuite/gcc.target/i386/avx512bw-vmovdqu16-2.c
index a61609c40d2..c6e3ebdc507 100644
--- a/gcc/testsuite/gcc.target/i386/avx512bw-vmovdqu16-2.c
+++ b/gcc/testsuite/gcc.target/i386/avx512bw-vmovdqu16-2.c
@@ -1,5 +1,5 @@
 /* { dg-do run } */
-/* { dg-options "-O2 -mavx512bw" } */
+/* { dg-options "-O2 -mavx512bw -Wno-address-of-packed-member" } */
 /* { dg-require-effective-target avx512bw } */
 
 #define AVX512BW
diff --git a/gcc/testsuite/gcc.target/i386/avx512f-vmovdqu32-2.c b/gcc/testsuite/gcc.target/i386/avx512f-vmovdqu32-2.c
index f2edc3dff7b..95a657fc5ff 100644
--- a/gcc/testsuite/gcc.target/i386/avx512f-vmovdqu32-2.c
+++ b/gcc/testsuite/gcc.target/i386/avx512f-vmovdqu32-2.c
@@ -1,5 +1,5 @@
 /* { dg-do run } */
-/* { dg-options "-O2 -mavx512f" } */
+/* { dg-options "-O2 -mavx512f -Wno-address-of-packed-member" } */
 /* { dg-require-effective-target avx512f } */
 
 #define AVX512F
diff --git a/gcc/testsuite/gcc.target/i386/avx512f-vmovdqu64-2.c b/gcc/testsuite/gcc.target/i386/avx512f-vmovdqu64-2.c
index 14176965ace..954b091d976 100644
--- a/gcc/testsuite/gcc.target/i386/avx512f-vmovdqu64-2.c
+++ b/gcc/testsuite/gcc.target/i386/avx512f-vmovdqu64-2.c
@@ -1,5 +1,5 @@
 /* { dg-do run } */
-/* { dg-options "-O2 -mavx512f" } */
+/* { dg-options "-O2 -mavx512f -Wno-address-of-packed-member" } */
 /* { dg-require-effective-target avx512f } */
 
 #define AVX512F
diff --git a/gcc/testsuite/gcc.target/i386/avx512vl-vmovdqu16-2.c b/gcc/testsuite/gcc.target/i386/avx512vl-vmovdqu16-2.c
index 45ae83d4552..81465f8d9a0 100644
--- a/gcc/testsuite/gcc.target/i386/avx512vl-vmovdqu16-2.c
+++ b/gcc/testsuite/gcc.target/i386/avx512vl-vmovdqu16-2.c
@@ -1,5 +1,5 @@
 /* { dg-do run } */
-/* { dg-options "-O2 -mavx512bw -mavx512vl" } */
+/* { dg-options "-O2 -mavx512bw -mavx512vl -Wno-address-of-packed-member" } */
 /* { dg-require-effective-target avx512vl } */
 /* { dg-require-effective-target avx512bw } */
 
diff --git a/gcc/testsuite/gcc.target/i386/avx512vl-vmovdqu32-2.c b/gcc/testsuite/gcc.target/i386/avx512vl-vmovdqu32-2.c
index 4b928d0cd42..19390664bd0 100644
--- a/gcc/testsuite/gcc.target/i386/avx512vl-vmovdqu32-2.c
+++ b/gcc/testsuite/gcc.target/i386/avx512vl-vmovdqu32-2.c
@@ -1,5 +1,5 @@
 /* { dg-do run } */
-/* { dg-options "-O2 -mavx512vl" } */
+/* { dg-options "-O2 -mavx512vl -Wno-address-of-packed-member" } */
 /* { dg-require-effective-target avx512vl } */
 
 #define AVX512VL
diff --git a/gcc/testsuite/gcc.target/i386/avx512vl-vmovdqu64-2.c b/gcc/testsuite/gcc.target/i386/avx512vl-vmovdqu64-2.c
index 1863ed3616f..aea0c12a5ff 100644
--- a/gcc/testsuite/gcc.target/i386/avx512vl-vmovdqu64-2.c
+++ b/gcc/testsuite/gcc.target/i386/avx512vl-vmovdqu64-2.c
@@ -1,5 +1,5 @@
 /* { dg-do run } */
-/* { dg-options "-O2 -mavx512vl" } */
+/* { dg-options "-O2 -mavx512vl -Wno-address-of-packed-member" } */
 /* { dg-require-effective-target avx512vl } */
 
 #define AVX512VL