[PR c++/84492] return stmt expr ending with overload

[Jason Merrill]

OK.

On Fri, Mar 2, 2018 at 2:57 AM, Alexandre Oliva <aoliva@redhat.com> wrote:
> On Feb 28, 2018, Jason Merrill <jason@redhat.com> wrote:
>
>> On Wed, Feb 28, 2018 at 7:06 AM, Alexandre Oliva <aoliva@redhat.com> wrote:
>>> We ICEd when returning a stmt expr that ends with an overloaded
>>> function.  It's ill-formed when we can't convert the function name to
>>> the return type, but we should say that, not ICE.
>
>> Hmm, what about the case where we could convert the function name to
>> the return type?  I think it should still be ill-formed for a
>> statement-expression to have an unresolved overload as its value.
>
> I was (not :-) thinking in those terms; I suppose one might wish ({x;})
> to be equivalent to (x), but one might also wish for stmt exprs to be
> self-contained, and I suppose you prefer the latter, or that there's
> consensus about how the stmt expr extension should be handled in this
> regard, so...
>
>> So finish_stmt_expr_expr should check type_unknown_p.
>
> [PR c++/84492] stmt expr ending with overload
>
> We ICEd when returning a stmt expr that ends with an overloaded
> function, because instantiate_type did not know what to do with
> STMT_EXPRs.  And it shouldn't have to: the expected type of a stmt
> expr cannot be used to resolve its value: an unresolved overload
> cannot supply the result of a stmt expr.  Catch that and report the
> error in the stmt expr before we have a chance to instantiate it.
>
> Regstrapped on i686- and x86_64-linux-gnu.  Ok?
>
> for  gcc/cp/ChangeLog
>
>         PR c++/84492
>         * semantics.c (finish_stmt_expr_expr): Reject unresolved
>         overloads used as stmt expr values.
>
> for  gcc/testsuite/ChangeLog
>
>         PR c++/84492
>         * g++.dg/pr84492.C: New.
> ---
>  gcc/cp/semantics.c             |    9 ++++++++-
>  gcc/testsuite/g++.dg/pr84492.C |   40 ++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 48 insertions(+), 1 deletion(-)
>  create mode 100644 gcc/testsuite/g++.dg/pr84492.C
>
> diff --git a/gcc/cp/semantics.c b/gcc/cp/semantics.c
> index 1ac1d23e7610..af401866b569 100644
> --- a/gcc/cp/semantics.c
> +++ b/gcc/cp/semantics.c
> @@ -2115,7 +2115,14 @@ finish_stmt_expr_expr (tree expr, tree stmt_expr)
>      {
>        tree type = TREE_TYPE (expr);
>
> -      if (processing_template_decl)
> +      if (type && type_unknown_p (type))
> +       {
> +         error ("a statement expression is an insufficient context"
> +                " for overload resolution");
> +         TREE_TYPE (stmt_expr) = error_mark_node;
> +         return error_mark_node;
> +       }
> +      else if (processing_template_decl)
>         {
>           expr = build_stmt (input_location, EXPR_STMT, expr);
>           expr = add_stmt (expr);
> diff --git a/gcc/testsuite/g++.dg/pr84492.C b/gcc/testsuite/g++.dg/pr84492.C
> new file mode 100644
> index 000000000000..1a2922096d19
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/pr84492.C
> @@ -0,0 +1,40 @@
> +// { dg-do compile }
> +// { dg-options "-fpermissive" }
> +
> +template<int> int foo()
> +{
> +  return ({ foo; }); // { dg-error "insufficient context" }
> +}
> +
> +int bar()
> +{
> +  return ({ foo; }); // { dg-error "insufficient context" }
> +}
> +
> +void bar(int);
> +
> +typedef void (*bart)(int);
> +
> +bart barf()
> +{
> +  return ({ bar; }); // { dg-error "insufficient context" }
> +}
> +
> +bool bark()
> +{
> +  return ({ barf; }); // ok, no overload
> +}
> +
> +template <typename T>
> +class C
> +{
> +  static int f();
> +  bool g()
> +  {
> +    return ({ f; }); // ok, no overload
> +  }
> +  bool g(int)
> +  {
> +    return ({ g; }); // { dg-error "insufficient context" }
> +  }
> +};
>
>
> --
> Alexandre Oliva, freedom fighter    http://FSFLA.org/~lxoliva/
> You must be the change you wish to see in the world. -- Gandhi
> Be Free! -- http://FSFLA.org/   FSF Latin America board member
> Free Software Evangelist|Red Hat Brasil GNU Toolchain Engineer