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

[Marek Polacek <polacek@redhat.com>]

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