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

[Jason Merrill <jason@redhat.com>]

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