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

[Jason Merrill <jason@redhat.com>]

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
>