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

[Patrick Palka <ppalka@redhat.com>]

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
> 
>