[PATCH] c++: fix ICE with designated initializer [PR110114]

[PATCH] c++: fix ICE with designated initializer [PR110114]

[Marek Polacek]

Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?

-- >8 --

r13-1227 added an assert checking that the index in a CONSTRUCTOR
is a FIELD_DECL.  That's a reasonable assumption but in this case
we never called reshape_init due to the type being incomplete, and
so the index remained an identifier node: get_class_binding never
got around to looking up the FIELD_DECL.

We can avoid the crash by returning early in build_aggr_conv; we'd
return NULL anyway due to:

  if (i < CONSTRUCTOR_NELTS (ctor))
    return NULL;

	PR c++/110114

gcc/cp/ChangeLog:

	* call.cc (build_aggr_conv): Return early if the type isn't
	complete.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp2a/desig28.C: New test.
	* g++.dg/cpp2a/desig29.C: New test.
---
 gcc/cp/call.cc                       |  5 +++++
 gcc/testsuite/g++.dg/cpp2a/desig28.C | 17 +++++++++++++++++
 gcc/testsuite/g++.dg/cpp2a/desig29.C | 10 ++++++++++
 3 files changed, 32 insertions(+)
 create mode 100644 gcc/testsuite/g++.dg/cpp2a/desig28.C
 create mode 100644 gcc/testsuite/g++.dg/cpp2a/desig29.C

diff --git a/gcc/cp/call.cc b/gcc/cp/call.cc
index b55230d98aa..0af20a81717 100644
--- a/gcc/cp/call.cc
+++ b/gcc/cp/call.cc
@@ -986,6 +986,11 @@ build_aggr_conv (tree type, tree ctor, int flags, tsubst_flags_t complain)
   tree empty_ctor = NULL_TREE;
   hash_set<tree, true> pset;
 
+  /* We've called complete_type on TYPE before calling this function, but
+     perhaps it wasn't successful.  */
+  if (!COMPLETE_TYPE_P (type))
+    return nullptr;
+
   /* We already called reshape_init in implicit_conversion, but it might not
      have done anything in the case of parenthesized aggr init.  */
 
diff --git a/gcc/testsuite/g++.dg/cpp2a/desig28.C b/gcc/testsuite/g++.dg/cpp2a/desig28.C
new file mode 100644
index 00000000000..b63265fea51
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/desig28.C
@@ -0,0 +1,17 @@
+// PR c++/110114
+// { dg-do compile { target c++20 } }
+
+struct A {
+    int a,b;
+};
+
+struct B;
+
+void foo(const A &) {}
+void foo(const B &) {}
+
+int
+main ()
+{
+  foo({.a=0});
+}
diff --git a/gcc/testsuite/g++.dg/cpp2a/desig29.C b/gcc/testsuite/g++.dg/cpp2a/desig29.C
new file mode 100644
index 00000000000..bd1a82b041d
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/desig29.C
@@ -0,0 +1,10 @@
+// PR c++/110114
+// { dg-do compile { target c++20 } }
+
+struct B;
+
+void foo(const B &) {}
+
+int main() {
+    foo({.a=0}); // { dg-error "invalid" }
+}

base-commit: 2971ff7b1d564ac04b537d907c70e6093af70832
-- 
2.41.0

Re: [PATCH] c++: fix ICE with designated initializer [PR110114]

[Patrick Palka]

On Wed, 19 Jul 2023, Marek Polacek wrote:

> Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?

LGTM.  It might be preferable to check COMPLETE_TYPE_P in the caller
instead, so that we avoid inspecting CLASSTYPE_NON_AGGREGATE on an
incomplete class type, and so that the caller doesn't "commit" to
building an aggregate conversion.

> 
> -- >8 --
> 
> r13-1227 added an assert checking that the index in a CONSTRUCTOR
> is a FIELD_DECL.  That's a reasonable assumption but in this case
> we never called reshape_init due to the type being incomplete, and
> so the index remained an identifier node: get_class_binding never
> got around to looking up the FIELD_DECL.
> 
> We can avoid the crash by returning early in build_aggr_conv; we'd
> return NULL anyway due to:
> 
>   if (i < CONSTRUCTOR_NELTS (ctor))
>     return NULL;
> 
> 	PR c++/110114
> 
> gcc/cp/ChangeLog:
> 
> 	* call.cc (build_aggr_conv): Return early if the type isn't
> 	complete.
> 
> gcc/testsuite/ChangeLog:
> 
> 	* g++.dg/cpp2a/desig28.C: New test.
> 	* g++.dg/cpp2a/desig29.C: New test.
> ---
>  gcc/cp/call.cc                       |  5 +++++
>  gcc/testsuite/g++.dg/cpp2a/desig28.C | 17 +++++++++++++++++
>  gcc/testsuite/g++.dg/cpp2a/desig29.C | 10 ++++++++++
>  3 files changed, 32 insertions(+)
>  create mode 100644 gcc/testsuite/g++.dg/cpp2a/desig28.C
>  create mode 100644 gcc/testsuite/g++.dg/cpp2a/desig29.C
> 
> diff --git a/gcc/cp/call.cc b/gcc/cp/call.cc
> index b55230d98aa..0af20a81717 100644
> --- a/gcc/cp/call.cc
> +++ b/gcc/cp/call.cc
> @@ -986,6 +986,11 @@ build_aggr_conv (tree type, tree ctor, int flags, tsubst_flags_t complain)
>    tree empty_ctor = NULL_TREE;
>    hash_set<tree, true> pset;
>  
> +  /* We've called complete_type on TYPE before calling this function, but
> +     perhaps it wasn't successful.  */
> +  if (!COMPLETE_TYPE_P (type))
> +    return nullptr;
> +
>    /* We already called reshape_init in implicit_conversion, but it might not
>       have done anything in the case of parenthesized aggr init.  */
>  
> diff --git a/gcc/testsuite/g++.dg/cpp2a/desig28.C b/gcc/testsuite/g++.dg/cpp2a/desig28.C
> new file mode 100644
> index 00000000000..b63265fea51
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/cpp2a/desig28.C
> @@ -0,0 +1,17 @@
> +// PR c++/110114
> +// { dg-do compile { target c++20 } }
> +
> +struct A {
> +    int a,b;
> +};
> +
> +struct B;
> +
> +void foo(const A &) {}
> +void foo(const B &) {}
> +
> +int
> +main ()
> +{
> +  foo({.a=0});
> +}
> diff --git a/gcc/testsuite/g++.dg/cpp2a/desig29.C b/gcc/testsuite/g++.dg/cpp2a/desig29.C
> new file mode 100644
> index 00000000000..bd1a82b041d
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/cpp2a/desig29.C
> @@ -0,0 +1,10 @@
> +// PR c++/110114
> +// { dg-do compile { target c++20 } }
> +
> +struct B;
> +
> +void foo(const B &) {}
> +
> +int main() {
> +    foo({.a=0}); // { dg-error "invalid" }
> +}
> 
> base-commit: 2971ff7b1d564ac04b537d907c70e6093af70832
> -- 
> 2.41.0
> 
> 

Re: [PATCH] c++: fix ICE with designated initializer [PR110114]

[Marek Polacek]

On Wed, Jul 19, 2023 at 02:32:15PM -0400, Patrick Palka wrote:
> On Wed, 19 Jul 2023, Marek Polacek wrote:
> 
> > Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
> 
> LGTM.  It might be preferable to check COMPLETE_TYPE_P in the caller
> instead, so that we avoid inspecting CLASSTYPE_NON_AGGREGATE on an
> incomplete class type, and so that the caller doesn't "commit" to
> building an aggregate conversion.

Perhaps.  I wanted to avoid the call to build_user_type_conversion_1.
I could add an early return to implicit_conversion_1 but I'd have to
move some code around not to check COMPLETE_TYPE_P before complete_type.
 
> > 
> > -- >8 --
> > 
> > r13-1227 added an assert checking that the index in a CONSTRUCTOR
> > is a FIELD_DECL.  That's a reasonable assumption but in this case
> > we never called reshape_init due to the type being incomplete, and
> > so the index remained an identifier node: get_class_binding never
> > got around to looking up the FIELD_DECL.
> > 
> > We can avoid the crash by returning early in build_aggr_conv; we'd
> > return NULL anyway due to:
> > 
> >   if (i < CONSTRUCTOR_NELTS (ctor))
> >     return NULL;
> > 
> > 	PR c++/110114
> > 
> > gcc/cp/ChangeLog:
> > 
> > 	* call.cc (build_aggr_conv): Return early if the type isn't
> > 	complete.
> > 
> > gcc/testsuite/ChangeLog:
> > 
> > 	* g++.dg/cpp2a/desig28.C: New test.
> > 	* g++.dg/cpp2a/desig29.C: New test.
> > ---
> >  gcc/cp/call.cc                       |  5 +++++
> >  gcc/testsuite/g++.dg/cpp2a/desig28.C | 17 +++++++++++++++++
> >  gcc/testsuite/g++.dg/cpp2a/desig29.C | 10 ++++++++++
> >  3 files changed, 32 insertions(+)
> >  create mode 100644 gcc/testsuite/g++.dg/cpp2a/desig28.C
> >  create mode 100644 gcc/testsuite/g++.dg/cpp2a/desig29.C
> > 
> > diff --git a/gcc/cp/call.cc b/gcc/cp/call.cc
> > index b55230d98aa..0af20a81717 100644
> > --- a/gcc/cp/call.cc
> > +++ b/gcc/cp/call.cc
> > @@ -986,6 +986,11 @@ build_aggr_conv (tree type, tree ctor, int flags, tsubst_flags_t complain)
> >    tree empty_ctor = NULL_TREE;
> >    hash_set<tree, true> pset;
> >  
> > +  /* We've called complete_type on TYPE before calling this function, but
> > +     perhaps it wasn't successful.  */
> > +  if (!COMPLETE_TYPE_P (type))
> > +    return nullptr;
> > +
> >    /* We already called reshape_init in implicit_conversion, but it might not
> >       have done anything in the case of parenthesized aggr init.  */
> >  
> > diff --git a/gcc/testsuite/g++.dg/cpp2a/desig28.C b/gcc/testsuite/g++.dg/cpp2a/desig28.C
> > new file mode 100644
> > index 00000000000..b63265fea51
> > --- /dev/null
> > +++ b/gcc/testsuite/g++.dg/cpp2a/desig28.C
> > @@ -0,0 +1,17 @@
> > +// PR c++/110114
> > +// { dg-do compile { target c++20 } }
> > +
> > +struct A {
> > +    int a,b;
> > +};
> > +
> > +struct B;
> > +
> > +void foo(const A &) {}
> > +void foo(const B &) {}
> > +
> > +int
> > +main ()
> > +{
> > +  foo({.a=0});
> > +}
> > diff --git a/gcc/testsuite/g++.dg/cpp2a/desig29.C b/gcc/testsuite/g++.dg/cpp2a/desig29.C
> > new file mode 100644
> > index 00000000000..bd1a82b041d
> > --- /dev/null
> > +++ b/gcc/testsuite/g++.dg/cpp2a/desig29.C
> > @@ -0,0 +1,10 @@
> > +// PR c++/110114
> > +// { dg-do compile { target c++20 } }
> > +
> > +struct B;
> > +
> > +void foo(const B &) {}
> > +
> > +int main() {
> > +    foo({.a=0}); // { dg-error "invalid" }
> > +}
> > 
> > base-commit: 2971ff7b1d564ac04b537d907c70e6093af70832
> > -- 
> > 2.41.0
> > 
> > 
> 

Marek

Re: [PATCH] c++: fix ICE with designated initializer [PR110114]

[Jason Merrill]

On 7/19/23 14:38, Marek Polacek wrote:
> On Wed, Jul 19, 2023 at 02:32:15PM -0400, Patrick Palka wrote:
>> On Wed, 19 Jul 2023, Marek Polacek wrote:
>>
>>> Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
>>
>> LGTM.  It might be preferable to check COMPLETE_TYPE_P in the caller
>> instead, so that we avoid inspecting CLASSTYPE_NON_AGGREGATE on an
>> incomplete class type, and so that the caller doesn't "commit" to
>> building an aggregate conversion.
> 
> Perhaps.  I wanted to avoid the call to build_user_type_conversion_1.
> I could add an early return to implicit_conversion_1 but I'd have to
> move some code around not to check COMPLETE_TYPE_P before complete_type.

Maybe return NULL for the incomplete case here, rather than just 
skipping reshape_init?

   /* Call reshape_init early to remove redundant braces.  */
   if (expr && BRACE_ENCLOSED_INITIALIZER_P (expr)
       && CLASS_TYPE_P (to)
       && COMPLETE_TYPE_P (complete_type (to))
       && !CLASSTYPE_NON_AGGREGATE (to))
     {
       expr = reshape_init (to, expr, complain);
       if (expr == error_mark_node)
         return NULL;
       from = TREE_TYPE (expr);
     }

If that doesn't work, the patch is fine as-is.

>>> -- >8 --
>>>
>>> r13-1227 added an assert checking that the index in a CONSTRUCTOR
>>> is a FIELD_DECL.  That's a reasonable assumption but in this case
>>> we never called reshape_init due to the type being incomplete, and
>>> so the index remained an identifier node: get_class_binding never
>>> got around to looking up the FIELD_DECL.
>>>
>>> We can avoid the crash by returning early in build_aggr_conv; we'd
>>> return NULL anyway due to:
>>>
>>>    if (i < CONSTRUCTOR_NELTS (ctor))
>>>      return NULL;
>>>
>>> 	PR c++/110114
>>>
>>> gcc/cp/ChangeLog:
>>>
>>> 	* call.cc (build_aggr_conv): Return early if the type isn't
>>> 	complete.
>>>
>>> gcc/testsuite/ChangeLog:
>>>
>>> 	* g++.dg/cpp2a/desig28.C: New test.
>>> 	* g++.dg/cpp2a/desig29.C: New test.
>>> ---
>>>   gcc/cp/call.cc                       |  5 +++++
>>>   gcc/testsuite/g++.dg/cpp2a/desig28.C | 17 +++++++++++++++++
>>>   gcc/testsuite/g++.dg/cpp2a/desig29.C | 10 ++++++++++
>>>   3 files changed, 32 insertions(+)
>>>   create mode 100644 gcc/testsuite/g++.dg/cpp2a/desig28.C
>>>   create mode 100644 gcc/testsuite/g++.dg/cpp2a/desig29.C
>>>
>>> diff --git a/gcc/cp/call.cc b/gcc/cp/call.cc
>>> index b55230d98aa..0af20a81717 100644
>>> --- a/gcc/cp/call.cc
>>> +++ b/gcc/cp/call.cc
>>> @@ -986,6 +986,11 @@ build_aggr_conv (tree type, tree ctor, int flags, tsubst_flags_t complain)
>>>     tree empty_ctor = NULL_TREE;
>>>     hash_set<tree, true> pset;
>>>   
>>> +  /* We've called complete_type on TYPE before calling this function, but
>>> +     perhaps it wasn't successful.  */
>>> +  if (!COMPLETE_TYPE_P (type))
>>> +    return nullptr;
>>> +
>>>     /* We already called reshape_init in implicit_conversion, but it might not
>>>        have done anything in the case of parenthesized aggr init.  */
>>>   
>>> diff --git a/gcc/testsuite/g++.dg/cpp2a/desig28.C b/gcc/testsuite/g++.dg/cpp2a/desig28.C
>>> new file mode 100644
>>> index 00000000000..b63265fea51
>>> --- /dev/null
>>> +++ b/gcc/testsuite/g++.dg/cpp2a/desig28.C
>>> @@ -0,0 +1,17 @@
>>> +// PR c++/110114
>>> +// { dg-do compile { target c++20 } }
>>> +
>>> +struct A {
>>> +    int a,b;
>>> +};
>>> +
>>> +struct B;
>>> +
>>> +void foo(const A &) {}
>>> +void foo(const B &) {}
>>> +
>>> +int
>>> +main ()
>>> +{
>>> +  foo({.a=0});
>>> +}
>>> diff --git a/gcc/testsuite/g++.dg/cpp2a/desig29.C b/gcc/testsuite/g++.dg/cpp2a/desig29.C
>>> new file mode 100644
>>> index 00000000000..bd1a82b041d
>>> --- /dev/null
>>> +++ b/gcc/testsuite/g++.dg/cpp2a/desig29.C
>>> @@ -0,0 +1,10 @@
>>> +// PR c++/110114
>>> +// { dg-do compile { target c++20 } }
>>> +
>>> +struct B;
>>> +
>>> +void foo(const B &) {}
>>> +
>>> +int main() {
>>> +    foo({.a=0}); // { dg-error "invalid" }
>>> +}
>>>
>>> base-commit: 2971ff7b1d564ac04b537d907c70e6093af70832
>>> -- 
>>> 2.41.0
>>>
>>>
>>
> 
> Marek
> 

[PATCH v2] c++: fix ICE with designated initializer [PR110114]

[Marek Polacek]

On Wed, Jul 19, 2023 at 03:24:10PM -0400, Jason Merrill wrote:
> On 7/19/23 14:38, Marek Polacek wrote:
> > On Wed, Jul 19, 2023 at 02:32:15PM -0400, Patrick Palka wrote:
> > > On Wed, 19 Jul 2023, Marek Polacek wrote:
> > > 
> > > > Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
> > > 
> > > LGTM.  It might be preferable to check COMPLETE_TYPE_P in the caller
> > > instead, so that we avoid inspecting CLASSTYPE_NON_AGGREGATE on an
> > > incomplete class type, and so that the caller doesn't "commit" to
> > > building an aggregate conversion.
> > 
> > Perhaps.  I wanted to avoid the call to build_user_type_conversion_1.
> > I could add an early return to implicit_conversion_1 but I'd have to
> > move some code around not to check COMPLETE_TYPE_P before complete_type.
> 
> Maybe return NULL for the incomplete case here, rather than just skipping
> reshape_init?
> 
>   /* Call reshape_init early to remove redundant braces.  */
>   if (expr && BRACE_ENCLOSED_INITIALIZER_P (expr)
>       && CLASS_TYPE_P (to)
>       && COMPLETE_TYPE_P (complete_type (to))
>       && !CLASSTYPE_NON_AGGREGATE (to))
>     {
>       expr = reshape_init (to, expr, complain);
>       if (expr == error_mark_node)
>         return NULL;
>       from = TREE_TYPE (expr);
>     }
> 
> If that doesn't work, the patch is fine as-is.

It does work, with one test tweak (which I don't think is a regression):
 
Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?

-- >8 --
r13-1227 added an assert checking that the index in a CONSTRUCTOR
is a FIELD_DECL.  That's a reasonable assumption but in this case
we never called reshape_init due to the type being incomplete, and
so the index remained an identifier node: get_class_binding never
got around to looking up the FIELD_DECL.

We can avoid the crash by returning early in implicit_conversion_1; we'd
return NULL anyway due to:

  if (i < CONSTRUCTOR_NELTS (ctor))
    return NULL;

in build_aggr_conv.

	PR c++/110114

gcc/cp/ChangeLog:

	* call.cc (implicit_conversion_1): Return early if the type isn't
	complete.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp0x/initlist100.C: Adjust expected diagnostic.
	* g++.dg/cpp2a/desig28.C: New test.
	* g++.dg/cpp2a/desig29.C: New test.
---
 gcc/cp/call.cc                           | 19 +++++++++++--------
 gcc/testsuite/g++.dg/cpp0x/initlist100.C |  4 ++--
 gcc/testsuite/g++.dg/cpp2a/desig28.C     | 17 +++++++++++++++++
 gcc/testsuite/g++.dg/cpp2a/desig29.C     | 10 ++++++++++
 4 files changed, 40 insertions(+), 10 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/cpp2a/desig28.C
 create mode 100644 gcc/testsuite/g++.dg/cpp2a/desig29.C

diff --git a/gcc/cp/call.cc b/gcc/cp/call.cc
index b55230d98aa..673ec91d60e 100644
--- a/gcc/cp/call.cc
+++ b/gcc/cp/call.cc
@@ -2059,15 +2059,18 @@ implicit_conversion_1 (tree to, tree from, tree expr, bool c_cast_p,
   complain &= ~tf_error;
 
   /* Call reshape_init early to remove redundant braces.  */
-  if (expr && BRACE_ENCLOSED_INITIALIZER_P (expr)
-      && CLASS_TYPE_P (to)
-      && COMPLETE_TYPE_P (complete_type (to))
-      && !CLASSTYPE_NON_AGGREGATE (to))
+  if (expr && BRACE_ENCLOSED_INITIALIZER_P (expr) && CLASS_TYPE_P (to))
     {
-      expr = reshape_init (to, expr, complain);
-      if (expr == error_mark_node)
-	return NULL;
-      from = TREE_TYPE (expr);
+      to = complete_type (to);
+      if (!COMPLETE_TYPE_P (to))
+	return nullptr;
+      if (!CLASSTYPE_NON_AGGREGATE (to))
+	{
+	  expr = reshape_init (to, expr, complain);
+	  if (expr == error_mark_node)
+	    return nullptr;
+	  from = TREE_TYPE (expr);
+	}
     }
 
   if (TYPE_REF_P (to))
diff --git a/gcc/testsuite/g++.dg/cpp0x/initlist100.C b/gcc/testsuite/g++.dg/cpp0x/initlist100.C
index 9d80a004c17..6865d34a6f9 100644
--- a/gcc/testsuite/g++.dg/cpp0x/initlist100.C
+++ b/gcc/testsuite/g++.dg/cpp0x/initlist100.C
@@ -2,9 +2,9 @@
 // { dg-do compile { target c++11 } }
 
 namespace std {
-template <class> class initializer_list;  // { dg-message "declaration" }
+template <class> class initializer_list;
 }
 
 template <typename T> struct B { B (std::initializer_list<T>); };
 struct C { virtual int foo (); };
-struct D : C {} d { B<C> { D {} } };  // { dg-error "incomplete|no matching" }
+struct D : C {} d { B<C> { D {} } };  // { dg-error "no matching" }
diff --git a/gcc/testsuite/g++.dg/cpp2a/desig28.C b/gcc/testsuite/g++.dg/cpp2a/desig28.C
new file mode 100644
index 00000000000..b63265fea51
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/desig28.C
@@ -0,0 +1,17 @@
+// PR c++/110114
+// { dg-do compile { target c++20 } }
+
+struct A {
+    int a,b;
+};
+
+struct B;
+
+void foo(const A &) {}
+void foo(const B &) {}
+
+int
+main ()
+{
+  foo({.a=0});
+}
diff --git a/gcc/testsuite/g++.dg/cpp2a/desig29.C b/gcc/testsuite/g++.dg/cpp2a/desig29.C
new file mode 100644
index 00000000000..bd1a82b041d
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/desig29.C
@@ -0,0 +1,10 @@
+// PR c++/110114
+// { dg-do compile { target c++20 } }
+
+struct B;
+
+void foo(const B &) {}
+
+int main() {
+    foo({.a=0}); // { dg-error "invalid" }
+}

base-commit: b86c0fe327a5196a316bd698d12765b08de5dce7
-- 
2.41.0

Re: [PATCH v2] c++: fix ICE with designated initializer [PR110114]

[Jason Merrill]

On 7/20/23 10:08, Marek Polacek wrote:
> On Wed, Jul 19, 2023 at 03:24:10PM -0400, Jason Merrill wrote:
>> On 7/19/23 14:38, Marek Polacek wrote:
>>> On Wed, Jul 19, 2023 at 02:32:15PM -0400, Patrick Palka wrote:
>>>> On Wed, 19 Jul 2023, Marek Polacek wrote:
>>>>
>>>>> Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
>>>>
>>>> LGTM.  It might be preferable to check COMPLETE_TYPE_P in the caller
>>>> instead, so that we avoid inspecting CLASSTYPE_NON_AGGREGATE on an
>>>> incomplete class type, and so that the caller doesn't "commit" to
>>>> building an aggregate conversion.
>>>
>>> Perhaps.  I wanted to avoid the call to build_user_type_conversion_1.
>>> I could add an early return to implicit_conversion_1 but I'd have to
>>> move some code around not to check COMPLETE_TYPE_P before complete_type.
>>
>> Maybe return NULL for the incomplete case here, rather than just skipping
>> reshape_init?
>>
>>    /* Call reshape_init early to remove redundant braces.  */
>>    if (expr && BRACE_ENCLOSED_INITIALIZER_P (expr)
>>        && CLASS_TYPE_P (to)
>>        && COMPLETE_TYPE_P (complete_type (to))
>>        && !CLASSTYPE_NON_AGGREGATE (to))
>>      {
>>        expr = reshape_init (to, expr, complain);
>>        if (expr == error_mark_node)
>>          return NULL;
>>        from = TREE_TYPE (expr);
>>      }
>>
>> If that doesn't work, the patch is fine as-is.
> 
> It does work, with one test tweak (which I don't think is a regression):
>   
> Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?

OK.

> -- >8 --
> r13-1227 added an assert checking that the index in a CONSTRUCTOR
> is a FIELD_DECL.  That's a reasonable assumption but in this case
> we never called reshape_init due to the type being incomplete, and
> so the index remained an identifier node: get_class_binding never
> got around to looking up the FIELD_DECL.
> 
> We can avoid the crash by returning early in implicit_conversion_1; we'd
> return NULL anyway due to:
> 
>    if (i < CONSTRUCTOR_NELTS (ctor))
>      return NULL;
> 
> in build_aggr_conv.
> 
> 	PR c++/110114
> 
> gcc/cp/ChangeLog:
> 
> 	* call.cc (implicit_conversion_1): Return early if the type isn't
> 	complete.
> 
> gcc/testsuite/ChangeLog:
> 
> 	* g++.dg/cpp0x/initlist100.C: Adjust expected diagnostic.
> 	* g++.dg/cpp2a/desig28.C: New test.
> 	* g++.dg/cpp2a/desig29.C: New test.
> ---
>   gcc/cp/call.cc                           | 19 +++++++++++--------
>   gcc/testsuite/g++.dg/cpp0x/initlist100.C |  4 ++--
>   gcc/testsuite/g++.dg/cpp2a/desig28.C     | 17 +++++++++++++++++
>   gcc/testsuite/g++.dg/cpp2a/desig29.C     | 10 ++++++++++
>   4 files changed, 40 insertions(+), 10 deletions(-)
>   create mode 100644 gcc/testsuite/g++.dg/cpp2a/desig28.C
>   create mode 100644 gcc/testsuite/g++.dg/cpp2a/desig29.C
> 
> diff --git a/gcc/cp/call.cc b/gcc/cp/call.cc
> index b55230d98aa..673ec91d60e 100644
> --- a/gcc/cp/call.cc
> +++ b/gcc/cp/call.cc
> @@ -2059,15 +2059,18 @@ implicit_conversion_1 (tree to, tree from, tree expr, bool c_cast_p,
>     complain &= ~tf_error;
>   
>     /* Call reshape_init early to remove redundant braces.  */
> -  if (expr && BRACE_ENCLOSED_INITIALIZER_P (expr)
> -      && CLASS_TYPE_P (to)
> -      && COMPLETE_TYPE_P (complete_type (to))
> -      && !CLASSTYPE_NON_AGGREGATE (to))
> +  if (expr && BRACE_ENCLOSED_INITIALIZER_P (expr) && CLASS_TYPE_P (to))
>       {
> -      expr = reshape_init (to, expr, complain);
> -      if (expr == error_mark_node)
> -	return NULL;
> -      from = TREE_TYPE (expr);
> +      to = complete_type (to);
> +      if (!COMPLETE_TYPE_P (to))
> +	return nullptr;
> +      if (!CLASSTYPE_NON_AGGREGATE (to))
> +	{
> +	  expr = reshape_init (to, expr, complain);
> +	  if (expr == error_mark_node)
> +	    return nullptr;
> +	  from = TREE_TYPE (expr);
> +	}
>       }
>   
>     if (TYPE_REF_P (to))
> diff --git a/gcc/testsuite/g++.dg/cpp0x/initlist100.C b/gcc/testsuite/g++.dg/cpp0x/initlist100.C
> index 9d80a004c17..6865d34a6f9 100644
> --- a/gcc/testsuite/g++.dg/cpp0x/initlist100.C
> +++ b/gcc/testsuite/g++.dg/cpp0x/initlist100.C
> @@ -2,9 +2,9 @@
>   // { dg-do compile { target c++11 } }
>   
>   namespace std {
> -template <class> class initializer_list;  // { dg-message "declaration" }
> +template <class> class initializer_list;
>   }
>   
>   template <typename T> struct B { B (std::initializer_list<T>); };
>   struct C { virtual int foo (); };
> -struct D : C {} d { B<C> { D {} } };  // { dg-error "incomplete|no matching" }
> +struct D : C {} d { B<C> { D {} } };  // { dg-error "no matching" }
> diff --git a/gcc/testsuite/g++.dg/cpp2a/desig28.C b/gcc/testsuite/g++.dg/cpp2a/desig28.C
> new file mode 100644
> index 00000000000..b63265fea51
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/cpp2a/desig28.C
> @@ -0,0 +1,17 @@
> +// PR c++/110114
> +// { dg-do compile { target c++20 } }
> +
> +struct A {
> +    int a,b;
> +};
> +
> +struct B;
> +
> +void foo(const A &) {}
> +void foo(const B &) {}
> +
> +int
> +main ()
> +{
> +  foo({.a=0});
> +}
> diff --git a/gcc/testsuite/g++.dg/cpp2a/desig29.C b/gcc/testsuite/g++.dg/cpp2a/desig29.C
> new file mode 100644
> index 00000000000..bd1a82b041d
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/cpp2a/desig29.C
> @@ -0,0 +1,10 @@
> +// PR c++/110114
> +// { dg-do compile { target c++20 } }
> +
> +struct B;
> +
> +void foo(const B &) {}
> +
> +int main() {
> +    foo({.a=0}); // { dg-error "invalid" }
> +}
> 
> base-commit: b86c0fe327a5196a316bd698d12765b08de5dce7