diff mbox series

c++: Treat unnamed bitfields as padding for __has_unique_object_representations [PR109096]

Message ID ZBApCMbOq6n+IGxA@tucnak
State Unresolved
Headers
Series c++: Treat unnamed bitfields as padding for __has_unique_object_representations [PR109096] |

Checks

Context Check Description
snail/gcc-patch-check warning Git am fail log

Commit Message

Jakub Jelinek March 14, 2023, 7:58 a.m. UTC 
  Hi!

As reported in the PR, for __has_unique_object_representations we
were treating unnamed bitfields as named ones, which is wrong, they
are actually padding.

THe following patch fixes that.  Ok for trunk (and what about release
branches later?)?

2023-03-14  Jakub Jelinek  <jakub@redhat.com>

	PR c++/109096
	* tree.cc (record_has_unique_obj_representations): Ignore unnamed
	bitfields.

	* g++.dg/cpp1z/has-unique-obj-representations3.C: New test.


	Jakub

Comments

Jason Merrill March 14, 2023, 2:35 p.m. UTC | #1 
On 3/14/23 03:58, Jakub Jelinek wrote:
> Hi!
> 
> As reported in the PR, for __has_unique_object_representations we
> were treating unnamed bitfields as named ones, which is wrong, they
> are actually padding.
> 
> THe following patch fixes that.  Ok for trunk (and what about release
> branches later?)?

OK.

> 2023-03-14  Jakub Jelinek  <jakub@redhat.com>
> 
> 	PR c++/109096
> 	* tree.cc (record_has_unique_obj_representations): Ignore unnamed
> 	bitfields.
> 
> 	* g++.dg/cpp1z/has-unique-obj-representations3.C: New test.
> 
> --- gcc/cp/tree.cc.jj	2023-03-10 10:06:40.247560614 +0100
> +++ gcc/cp/tree.cc	2023-03-13 10:38:03.394836926 +0100
> @@ -4851,7 +4851,7 @@ record_has_unique_obj_representations (c
>   						    DECL_SIZE (field)))
>   	  return false;
>         }
> -    else if (DECL_C_BIT_FIELD (field))
> +    else if (DECL_C_BIT_FIELD (field) && !DECL_UNNAMED_BIT_FIELD (field))
>         {
>   	tree btype = DECL_BIT_FIELD_TYPE (field);
>   	if (!type_has_unique_obj_representations (btype))
> @@ -4862,7 +4862,7 @@ record_has_unique_obj_representations (c
>   
>     offset_int cur = 0;
>     for (tree field = TYPE_FIELDS (t); field; field = DECL_CHAIN (field))
> -    if (TREE_CODE (field) == FIELD_DECL)
> +    if (TREE_CODE (field) == FIELD_DECL && !DECL_UNNAMED_BIT_FIELD (field))
>         {
>   	offset_int fld = wi::to_offset (DECL_FIELD_OFFSET (field));
>   	offset_int bitpos = wi::to_offset (DECL_FIELD_BIT_OFFSET (field));
> --- gcc/testsuite/g++.dg/cpp1z/has-unique-obj-representations3.C.jj	2023-03-13 10:50:21.705127719 +0100
> +++ gcc/testsuite/g++.dg/cpp1z/has-unique-obj-representations3.C	2023-03-13 10:50:17.751185067 +0100
> @@ -0,0 +1,10 @@
> +// PR c++/109096
> +// { dg-do compile { target c++11 } }
> +
> +#define INTB (__SIZEOF_INT__ * __CHAR_BIT__)
> +struct U { int i : INTB * 3 / 4; int : INTB / 4; };
> +struct V { int : INTB * 3 / 4; int j : INTB / 4; };
> +struct W { int i; int : 0; int j; };
> +static_assert (__has_unique_object_representations (U) == false, "");
> +static_assert (__has_unique_object_representations (V) == false, "");
> +static_assert (sizeof (W) != 2 * sizeof (int) || __has_unique_object_representations (W) == true, "");
> 
> 	Jakub
>
diff mbox series

Patch

--- gcc/cp/tree.cc.jj	2023-03-10 10:06:40.247560614 +0100
+++ gcc/cp/tree.cc	2023-03-13 10:38:03.394836926 +0100
@@ -4851,7 +4851,7 @@  record_has_unique_obj_representations (c
 						    DECL_SIZE (field)))
 	  return false;
       }
-    else if (DECL_C_BIT_FIELD (field))
+    else if (DECL_C_BIT_FIELD (field) && !DECL_UNNAMED_BIT_FIELD (field))
       {
 	tree btype = DECL_BIT_FIELD_TYPE (field);
 	if (!type_has_unique_obj_representations (btype))
@@ -4862,7 +4862,7 @@  record_has_unique_obj_representations (c
 
   offset_int cur = 0;
   for (tree field = TYPE_FIELDS (t); field; field = DECL_CHAIN (field))
-    if (TREE_CODE (field) == FIELD_DECL)
+    if (TREE_CODE (field) == FIELD_DECL && !DECL_UNNAMED_BIT_FIELD (field))
       {
 	offset_int fld = wi::to_offset (DECL_FIELD_OFFSET (field));
 	offset_int bitpos = wi::to_offset (DECL_FIELD_BIT_OFFSET (field));
--- gcc/testsuite/g++.dg/cpp1z/has-unique-obj-representations3.C.jj	2023-03-13 10:50:21.705127719 +0100
+++ gcc/testsuite/g++.dg/cpp1z/has-unique-obj-representations3.C	2023-03-13 10:50:17.751185067 +0100
@@ -0,0 +1,10 @@ 
+// PR c++/109096
+// { dg-do compile { target c++11 } }
+
+#define INTB (__SIZEOF_INT__ * __CHAR_BIT__)
+struct U { int i : INTB * 3 / 4; int : INTB / 4; };
+struct V { int : INTB * 3 / 4; int j : INTB / 4; };
+struct W { int i; int : 0; int j; };
+static_assert (__has_unique_object_representations (U) == false, "");
+static_assert (__has_unique_object_representations (V) == false, "");
+static_assert (sizeof (W) != 2 * sizeof (int) || __has_unique_object_representations (W) == true, "");