Re: [PATCH] c++: ICE with deferred noexcept when deducing targs [PR82099]

[Jason Merrill <jason@redhat.com>]

On 1/4/21 8:31 PM, Marek Polacek wrote:
> In this test we ICE in type_throw_all_p because it got a deferred
> noexcept which it shouldn't.  Here's the story:
> 
> In noexcept61.C, we call bar, so we perform overload resolution.  When
> adding the (only) candidate, we need to deduce template arguments, so
> call fn_type_unification as usually.  That deduces U to
> 
>    void (*) (int &, int &)
> 
> which is correct, but its noexcept-spec is deferred_noexcept.  Then
> we call add_function_candidate (bar), wherein we try to create an
> implicit conversion sequence for every argument.  Since baz<int> is
> of unknown type, we instantiate_type it; it is a TEMPLATE_ID_EXPR
> so that calls resolve_address_of_overloaded_function.  But we crash
> there, because target_type contains the deferred_noexcept.
> 
> So we need to maybe_instantiate_noexcept before we can compare types.
> resolve_overloaded_unification seemed like the appropriate spot, now
> fn_type_unification produces the function type with its noexcept-spec
> instantiated.  This shouldn't go against CWG 1330 because here we
> really need to instantiate the noexcept-spec.
> 
> This also fixes class-deduction76.C, a dg-ice test I recently added,
> therefore this fix also fixes c++/90799, yay.
> 
> Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?

OK.

> gcc/cp/ChangeLog:
> 
> 	PR c++/82099
> 	* pt.c (resolve_overloaded_unification): Call
> 	maybe_instantiate_noexcept after instantiating the function
> 	decl.
> 
> gcc/testsuite/ChangeLog:
> 
> 	PR c++/82099
> 	* g++.dg/cpp1z/class-deduction76.C: Remove dg-ice.
> 	* g++.dg/cpp0x/noexcept61.C: New test.
> ---
>   gcc/cp/pt.c                                    |  3 +++
>   gcc/testsuite/g++.dg/cpp0x/noexcept61.C        | 17 +++++++++++++++++
>   gcc/testsuite/g++.dg/cpp1z/class-deduction76.C |  1 -
>   3 files changed, 20 insertions(+), 1 deletion(-)
>   create mode 100644 gcc/testsuite/g++.dg/cpp0x/noexcept61.C
> 
> diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
> index 062ef858501..0d061adc2ed 100644
> --- a/gcc/cp/pt.c
> +++ b/gcc/cp/pt.c
> @@ -22373,6 +22373,9 @@ resolve_overloaded_unification (tree tparms,
>   		  --function_depth;
>   		}
>   
> +	      if (flag_noexcept_type)
> +		maybe_instantiate_noexcept (fn, tf_none);
> +
>   	      elem = TREE_TYPE (fn);
>   	      if (try_one_overload (tparms, targs, tempargs, parm,
>   				    elem, strict, sub_strict, addr_p, explain_p)
> diff --git a/gcc/testsuite/g++.dg/cpp0x/noexcept61.C b/gcc/testsuite/g++.dg/cpp0x/noexcept61.C
> new file mode 100644
> index 00000000000..653cd7e6680
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/cpp0x/noexcept61.C
> @@ -0,0 +1,17 @@
> +// PR c++/82099
> +// { dg-do compile { target c++11 } }
> +
> +template <typename T, typename U>
> +void bar (T &x, T &y, U u)
> +{
> +  u (x, y);
> +}
> +
> +template <typename T>
> +void baz (T &x, T &y) noexcept (noexcept (x == y));
> +
> +void
> +foo (int x, int y)
> +{
> +  bar (x, y, baz<int>);
> +}
> diff --git a/gcc/testsuite/g++.dg/cpp1z/class-deduction76.C b/gcc/testsuite/g++.dg/cpp1z/class-deduction76.C
> index 23bb6e8fa9a..a131a386baa 100644
> --- a/gcc/testsuite/g++.dg/cpp1z/class-deduction76.C
> +++ b/gcc/testsuite/g++.dg/cpp1z/class-deduction76.C
> @@ -1,6 +1,5 @@
>   // PR c++/90799
>   // { dg-do compile { target c++17 } }
> -// { dg-ice "unify" }
>   
>   template<class T>
>   void foo() noexcept(T::value);
> 
> base-commit: f262a3518877ccce9ed41b2e152c3a3564727bd6
>