Re: C++ PATCH for c++/48113 (SFINAE bug causing bind regression in libstdc++)

[Richard Guenther <richard dot guenther at gmail dot com>]

On Wed, Mar 16, 2011 at 8:51 PM, Jason Merrill <jason@redhat.com> wrote:
> convert_for_initialization is sfinae-enabled, but it was calling
> ocp_convert, which is not. ?This patch changes it to use the newer
> perform_implicit_conversion_flags instead. ?To make that work, I needed to
> add support for LOOKUP_PREFER_RVALUE to that code path.
>
> Tested x86_64-pc-linux-gnu, applying to trunk.
>
> Also OK for 4.6.0? ?The risk is that swapping to
> perform_implicit_conversion_flags will have other differences of behavior,
> but the library regression seems pretty major, so I think it's worth the
> risk.

Ok for 4.6.0.  I guess we need to do a RC2 anyway.

Thanks,
Richard.

> commit fb46d045ce1b2ee71402942a42b61921cec7c41f
> Author: Jason Merrill <jason@redhat.com>
> Date: ? Mon Mar 14 14:49:58 2011 -0400
>
> ? ? ? ?PR c++/48113
> ? ? ? ?* typeck.c (convert_for_initialization): Use
> ? ? ? ?perform_implicit_conversion_flags.
> ? ? ? ?* call.c (standard_conversion): If LOOKUP_PREFER_RVALUE, set
> ? ? ? ?rvaluedness_matches_p on ck_rvalue.
> ? ? ? ?(convert_like_real) [ck_rvalue]: And restore it here.
>
> diff --git a/gcc/cp/call.c b/gcc/cp/call.c
> index f75c248..436c956 100644
> --- a/gcc/cp/call.c
> +++ b/gcc/cp/call.c
> @@ -98,7 +98,9 @@ struct conversion {
> ? BOOL_BITFIELD base_p : 1;
> ? /* If KIND is ck_ref_bind, true when either an lvalue reference is
> ? ? ?being bound to an lvalue expression or an rvalue reference is
> - ? ? being bound to an rvalue expression. */
> + ? ? being bound to an rvalue expression. ?If KIND is ck_rvalue,
> + ? ? true when we should treat an lvalue as an rvalue (12.8p33). ?If
> + ? ? KIND is ck_base, always false. ?*/
> ? BOOL_BITFIELD rvaluedness_matches_p: 1;
> ? BOOL_BITFIELD check_narrowing: 1;
> ? /* The type of the expression resulting from the conversion. ?*/
> @@ -897,6 +899,8 @@ standard_conversion (tree to, tree from, tree expr, bool
> c_cast_p,
> ? ? ? ? ? ?}
> ? ? ? ?}
> ? ? ? conv = build_conv (ck_rvalue, from, conv);
> + ? ? ?if (flags & LOOKUP_PREFER_RVALUE)
> + ? ? ? conv->rvaluedness_matches_p = true;
> ? ? }
>
> ? ?/* Allow conversion between `__complex__' data types. ?*/
> @@ -5489,6 +5493,8 @@ convert_like_real (conversion *convs, tree expr, tree
> fn, int argnum,
> ? ? ? ? ? conversion (i.e. the second step of copy-initialization), so
> ? ? ? ? ? don't allow any more. ?*/
> ? ? ? ?flags |= LOOKUP_NO_CONVERSION;
> + ? ? ?if (convs->rvaluedness_matches_p)
> + ? ? ? flags |= LOOKUP_PREFER_RVALUE;
> ? ? ? if (TREE_CODE (expr) == TARGET_EXPR
> ? ? ? ? ?&& TARGET_EXPR_LIST_INIT_P (expr))
> ? ? ? ?/* Copy-list-initialization doesn't actually involve a copy. ?*/
> diff --git a/gcc/cp/typeck.c b/gcc/cp/typeck.c
> index c062f0f..0e8a6d7 100644
> --- a/gcc/cp/typeck.c
> +++ b/gcc/cp/typeck.c
> @@ -7454,7 +7454,7 @@ convert_for_initialization (tree exp, tree type, tree
> rhs, int flags,
> ? ? return rhs;
>
> ? if (MAYBE_CLASS_TYPE_P (type))
> - ? ?return ocp_convert (type, rhs, CONV_IMPLICIT|CONV_FORCE_TEMP, flags);
> + ? ?return perform_implicit_conversion_flags (type, rhs, complain, flags);
>
> ? return convert_for_assignment (type, rhs, errtype, fndecl, parmnum,
> ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? complain, flags);
> diff --git a/gcc/testsuite/g++.dg/cpp0x/initlist38.C
> b/gcc/testsuite/g++.dg/cpp0x/initlist38.C
> index 818d69a..32e20d5 100644
> --- a/gcc/testsuite/g++.dg/cpp0x/initlist38.C
> +++ b/gcc/testsuite/g++.dg/cpp0x/initlist38.C
> @@ -17,5 +17,5 @@ int main()
> ? f({});
> ? B b0 = { };
> ? B b1 { }; ? ?// OK, uses #1
> - ?B b2 { 1 }; ?// { dg-error "conversion" }
> + ?B b2 { 1 }; ?// { dg-error "could not convert" }
> ?}
> diff --git a/gcc/testsuite/g++.dg/cpp0x/pr45908.C
> b/gcc/testsuite/g++.dg/cpp0x/pr45908.C
> index 1a821e5..3a85088 100644
> --- a/gcc/testsuite/g++.dg/cpp0x/pr45908.C
> +++ b/gcc/testsuite/g++.dg/cpp0x/pr45908.C
> @@ -14,5 +14,5 @@ struct vector {
> ?class block {
> ? ? vector v;
> ? ? auto end() const -> decltype(v.begin())
> - ? ?{ return v.begin(); } // { dg-error "conversion" }
> + ? ?{ return v.begin(); } // { dg-error "could not convert" }
> ?};
> diff --git a/gcc/testsuite/g++.dg/cpp0x/sfinae6.C
> b/gcc/testsuite/g++.dg/cpp0x/sfinae6.C
> new file mode 100644
> index 0000000..401d536
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/cpp0x/sfinae6.C
> @@ -0,0 +1,31 @@
> +// PR c++/48113
> +// { dg-options -std=c++0x }
> +
> +template<typename T> T declval();
> +
> +struct tuple { };
> +
> +struct F1
> +{
> + ? ?void operator()(tuple, int);
> +};
> +
> +typedef void (*F2)(tuple, int);
> +
> +template<typename F, typename T>
> +struct Bind
> +{
> + ? ?template<typename A,
> + ? ? ? ? ? ? typename R = decltype( F()(declval<T&>(), A()) )>
> + ? ?R f(A);
> +
> + ? ?template<typename A,
> + ? ? ? ? ? ? typename R = decltype( F()(declval<volatile T&>(), A()) )>
> + ? ?R f(A) volatile;
> +};
> +
> +int main()
> +{
> + ? ?Bind<F1, tuple>().f(0); ?// OK
> + ? ?Bind<F2, tuple>().f(0); ?// ERROR, should be OK
> +}
> diff --git a/gcc/testsuite/g++.old-deja/g++.jason/conversion11.C
> b/gcc/testsuite/g++.old-deja/g++.jason/conversion11.C
> index 607cf9c..6621a27 100644
> --- a/gcc/testsuite/g++.old-deja/g++.jason/conversion11.C
> +++ b/gcc/testsuite/g++.old-deja/g++.jason/conversion11.C
> @@ -21,7 +21,7 @@ void DoSomething(Ding A);
>
> ?void foo(Something* pX)
> ?{
> - ?DoSomething(1); ? ? ? ? ? ? ?// { dg-error "conversion" }
> + ?DoSomething(1); ? ? ? ? ? ? ?// { dg-error "could not convert" }
> ? pX->DoSomething(1); ? ? ? ? ?// { dg-error "no matching" }
> ? // { dg-message "candidate" "candidate note" { target *-*-* } 25 }
> ? (*pX).DoSomething(1); ? ? ? ? ? ? ? ?// { dg-error "no matching" }
> diff --git a/gcc/testsuite/g++.old-deja/g++.law/arg11.C
> b/gcc/testsuite/g++.old-deja/g++.law/arg11.C
> index fc590c4..fc93579 100644
> --- a/gcc/testsuite/g++.old-deja/g++.law/arg11.C
> +++ b/gcc/testsuite/g++.old-deja/g++.law/arg11.C
> @@ -16,7 +16,7 @@ void function(Ack);
> ?int
> ?foo(S *o)
> ?{ // Neither call has a usable constructor for conversions of char[5] to
> Ack.
> - ?function("adsf");// { dg-error "conversion" }
> + ?function("adsf");// { dg-error "could not convert" }
> ? o->method("adsf");// { dg-error "no matching" }
> ? // { dg-message "candidate" "candidate note" { target *-*-* } 20 }
> ? return 0;
>
>