c-family: -Waddress-of-packed-member and casts

-Waddress-of-packed-member, in addition to the documented warning about
actually taking the address of a packed member, also warns about casting
from a pointer to a TYPE_PACKED type to a pointer to a type with greater
alignment.

This wrongly warns if the source is a pointer to enum when -fshort-enums
is on, since that is also represented by TYPE_PACKED.

And there's already -Wcast-align to catch casting from pointer to less
aligned type (packed or otherwise) to pointer to more aligned type; even
apart from the enum problem, this seems like a somewhat arbitrary subset of
that warning.

So, this patch removes the undocumented type-based warning from
-Waddress-of-packed-member.  Some of the tests where the warning is
desirable I changed to use -Wcast-align=strict instead.  The ones that
require -Wno-incompatible-pointer-types I just removed.

gcc/c-family/ChangeLog:

	* c-warn.cc (check_address_or_pointer_of_packed_member):
	Remove warning based on TYPE_PACKED.

gcc/testsuite/ChangeLog:

	* c-c++-common/Waddress-of-packed-member-1.c: Don't expect
	a warning on the cast cases.
	* c-c++-common/pr51628-35.c: Use -Wcast-align=strict.
	* g++.dg/warn/Waddress-of-packed-member3.C: Likewise.
	* gcc.dg/pr88928.c: Likewise.
	* gcc.dg/pr51628-20.c: Removed.
	* gcc.dg/pr51628-21.c: Removed.
	* gcc.dg/pr51628-25.c: Removed.

1 files changed, 3 insertions, 55 deletions

diff --git a/gcc/c-family/c-warn.cc b/gcc/c-family/c-warn.cc
index d2938b9..2a399ba 100644
--- a/gcc/c-family/c-warn.cc
+++ b/gcc/c-family/c-warn.cc
@@ -2991,10 +2991,9 @@ check_alignment_of_packed_member (tree type, tree field, bool rvalue)
   return NULL_TREE;
 }
 
-/* Return struct or union type if the right hand value, RHS:
-   1. Is a pointer value which isn't aligned to a pointer type TYPE.
-   2. Is an address which takes the unaligned address of packed member
-      of struct or union when assigning to TYPE.
+/* Return struct or union type if the right hand value, RHS
+   is an address which takes the unaligned address of packed member
+   of struct or union when assigning to TYPE.
    Otherwise, return NULL_TREE.  */
 
 static tree
@@ -3021,57 +3020,6 @@ check_address_or_pointer_of_packed_member (tree type, tree rhs)
 
   type = TREE_TYPE (type);
 
-  if (TREE_CODE (rhs) == PARM_DECL
-      || VAR_P (rhs)
-      || TREE_CODE (rhs) == CALL_EXPR)
-    {
-      tree rhstype = TREE_TYPE (rhs);
-      if (TREE_CODE (rhs) == CALL_EXPR)
-	{
-	  rhs = CALL_EXPR_FN (rhs);	/* Pointer expression.  */
-	  if (rhs == NULL_TREE)
-	    return NULL_TREE;
-	  rhs = TREE_TYPE (rhs);	/* Pointer type.  */
-	  /* We could be called while processing a template and RHS could be
-	     a functor.  In that case it's a class, not a pointer.  */
-	  if (!rhs || !POINTER_TYPE_P (rhs))
-	    return NULL_TREE;
-	  rhs = TREE_TYPE (rhs);	/* Function type.  */
-	  rhstype = TREE_TYPE (rhs);
-	  if (!rhstype || !POINTER_TYPE_P (rhstype))
-	    return NULL_TREE;
-	  rvalue = true;
-	}
-      if (rvalue && POINTER_TYPE_P (rhstype))
-	rhstype = TREE_TYPE (rhstype);
-      while (TREE_CODE (rhstype) == ARRAY_TYPE)
-	rhstype = TREE_TYPE (rhstype);
-      if (TYPE_PACKED (rhstype))
-	{
-	  unsigned int type_align = min_align_of_type (type);
-	  unsigned int rhs_align = min_align_of_type (rhstype);
-	  if (rhs_align < type_align)
-	    {
-	      auto_diagnostic_group d;
-	      location_t location = EXPR_LOC_OR_LOC (rhs, input_location);
-	      if (warning_at (location, OPT_Waddress_of_packed_member,
-			      "converting a packed %qT pointer (alignment %d) "
-			      "to a %qT pointer (alignment %d) may result in "
-			      "an unaligned pointer value",
-			      rhstype, rhs_align, type, type_align))
-		{
-		  tree decl = TYPE_STUB_DECL (rhstype);
-		  if (decl)
-		    inform (DECL_SOURCE_LOCATION (decl), "defined here");
-		  decl = TYPE_STUB_DECL (type);
-		  if (decl)
-		    inform (DECL_SOURCE_LOCATION (decl), "defined here");
-		}
-	    }
-	}
-      return NULL_TREE;
-    }
-
   tree context = NULL_TREE;
 
   /* Check alignment of the object.  */