[C++] Fix -std=c++17 and earlier handling of CLASSTYPE_NON_AGGREGATE (PR c++/92869)
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Message ID 20191210204717.GF10088@tucnak
State New
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  • [C++] Fix -std=c++17 and earlier handling of CLASSTYPE_NON_AGGREGATE (PR c++/92869)
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Commit Message

Jakub Jelinek Dec. 10, 2019, 8:47 p.m. UTC
Hi!

In C++20, types with user-declared constructors are not aggregate types,
while in C++17 only types with user-provided or explicit constructors.
In check_bases_and_members we handle it properly:
  CLASSTYPE_NON_AGGREGATE (t)
    |= ((cxx_dialect < cxx2a
         ? type_has_user_provided_or_explicit_constructor (t)
         : TYPE_HAS_USER_CONSTRUCTOR (t))
        || TYPE_POLYMORPHIC_P (t));
but for templates the code right now behaves the C++20 way regardless of the
selected standard.

The following patch tweaks finish_struct to match check_bases_and_members.
I had to add !CLASSTYPE_NON_AGGREGATE check because
type_has_user_provided_or_explicit_constructor -> user_provided_p ICEd
on inherited ctors represented as USING_DECLs.

Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

2019-12-10  Jakub Jelinek  <jakub@redhat.com>

	PR c++/92869
	* class.c (finish_struct): For C++17 and earlier, check
	type_has_user_provided_or_explicit_constructor rather than
	TYPE_HAS_USER_CONSTRUCTOR whether to set CLASSTYPE_NON_AGGREGATE.

	* g++.dg/cpp0x/aggr3.C: New test.


	Jakub

Comments

Jason Merrill Dec. 11, 2019, 6:32 p.m. UTC | #1
On 12/10/19 3:47 PM, Jakub Jelinek wrote:
> Hi!
> 
> In C++20, types with user-declared constructors are not aggregate types,
> while in C++17 only types with user-provided or explicit constructors.
> In check_bases_and_members we handle it properly:
>    CLASSTYPE_NON_AGGREGATE (t)
>      |= ((cxx_dialect < cxx2a
>           ? type_has_user_provided_or_explicit_constructor (t)
>           : TYPE_HAS_USER_CONSTRUCTOR (t))
>          || TYPE_POLYMORPHIC_P (t));
> but for templates the code right now behaves the C++20 way regardless of the
> selected standard.
> 
> The following patch tweaks finish_struct to match check_bases_and_members.
> I had to add !CLASSTYPE_NON_AGGREGATE check because
> type_has_user_provided_or_explicit_constructor -> user_provided_p ICEd
> on inherited ctors represented as USING_DECLs.
> 
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

OK.

> 2019-12-10  Jakub Jelinek  <jakub@redhat.com>
> 
> 	PR c++/92869
> 	* class.c (finish_struct): For C++17 and earlier, check
> 	type_has_user_provided_or_explicit_constructor rather than
> 	TYPE_HAS_USER_CONSTRUCTOR whether to set CLASSTYPE_NON_AGGREGATE.
> 
> 	* g++.dg/cpp0x/aggr3.C: New test.
> 
> --- gcc/cp/class.c.jj	2019-12-06 00:40:44.525629037 +0100
> +++ gcc/cp/class.c	2019-12-10 14:18:41.171380767 +0100
> @@ -7456,7 +7456,13 @@ finish_struct (tree t, tree attributes)
>         /* Remember current #pragma pack value.  */
>         TYPE_PRECISION (t) = maximum_field_alignment;
>   
> -      if (TYPE_HAS_USER_CONSTRUCTOR (t))
> +      if (cxx_dialect < cxx2a)
> +	{
> +	  if (!CLASSTYPE_NON_AGGREGATE (t)
> +	      && type_has_user_provided_or_explicit_constructor (t))
> +	    CLASSTYPE_NON_AGGREGATE (t) = 1;
> +	}
> +      else if (TYPE_HAS_USER_CONSTRUCTOR (t))
>   	CLASSTYPE_NON_AGGREGATE (t) = 1;
>   
>         /* Fix up any variants we've already built.  */
> --- gcc/testsuite/g++.dg/cpp0x/aggr3.C.jj	2019-12-10 14:25:22.344231923 +0100
> +++ gcc/testsuite/g++.dg/cpp0x/aggr3.C	2019-12-10 14:23:31.700927787 +0100
> @@ -0,0 +1,20 @@
> +// PR c++/92869
> +// { dg-do compile { target c++11 } }
> +
> +struct A {
> +  A () = default;
> +  A (const A &) = default;
> +  A (A &&) = default;
> +  int arr[3];
> +};
> +
> +template <typename T, int N>
> +struct B {
> +  B () = default;
> +  B (const B &) = default;
> +  B (B &&) = default;
> +  T arr[N];
> +};
> +
> +A a = { { 1, 2, 3 } };		// { dg-error "could not convert" "" { target c++2a } }
> +B<int, 3> b = { { 1, 2, 3 } };	// { dg-error "could not convert" "" { target c++2a } }
> 
> 	Jakub
>

Patch
diff mbox series

--- gcc/cp/class.c.jj	2019-12-06 00:40:44.525629037 +0100
+++ gcc/cp/class.c	2019-12-10 14:18:41.171380767 +0100
@@ -7456,7 +7456,13 @@  finish_struct (tree t, tree attributes)
       /* Remember current #pragma pack value.  */
       TYPE_PRECISION (t) = maximum_field_alignment;
 
-      if (TYPE_HAS_USER_CONSTRUCTOR (t))
+      if (cxx_dialect < cxx2a)
+	{
+	  if (!CLASSTYPE_NON_AGGREGATE (t)
+	      && type_has_user_provided_or_explicit_constructor (t))
+	    CLASSTYPE_NON_AGGREGATE (t) = 1;
+	}
+      else if (TYPE_HAS_USER_CONSTRUCTOR (t))
 	CLASSTYPE_NON_AGGREGATE (t) = 1;
 
       /* Fix up any variants we've already built.  */
--- gcc/testsuite/g++.dg/cpp0x/aggr3.C.jj	2019-12-10 14:25:22.344231923 +0100
+++ gcc/testsuite/g++.dg/cpp0x/aggr3.C	2019-12-10 14:23:31.700927787 +0100
@@ -0,0 +1,20 @@ 
+// PR c++/92869
+// { dg-do compile { target c++11 } }
+
+struct A {
+  A () = default;
+  A (const A &) = default;
+  A (A &&) = default;
+  int arr[3];
+};
+
+template <typename T, int N>
+struct B {
+  B () = default;
+  B (const B &) = default;
+  B (B &&) = default;
+  T arr[N];
+};
+
+A a = { { 1, 2, 3 } };		// { dg-error "could not convert" "" { target c++2a } }
+B<int, 3> b = { { 1, 2, 3 } };	// { dg-error "could not convert" "" { target c++2a } }