On Thu, 3 Feb 2022, Jason Merrill wrote:
> On 2/3/22 14:58, Patrick Palka wrote:
> > When synthesizing a defaulted comparison op from
> > maybe_instantiate_noexcept, we seem to be forgetting to instantiate the
> > noexcept-spec afterwards.
>
> Hmm, there shouldn't be any need to instantiate the noexcept-spec afterwards,
> it should have been set by ~comp_info.
It appears the comp_info class sets the noexcept-spec only if the
comparison function hasn't been declared with an explicit noexcept-spec.
Otherwise the class doesn't touch the noexcept-spec, and it remains a
DEFERRED_NOEXCEPT with non-NULL DEFERRED_NOEXCEPT_PATTERN.
>
> > Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for
> > trunk and perhaps 11?
> >
> > PR c++/96242
> >
> > gcc/cp/ChangeLog:
> >
> > * pt.cc (maybe_instantiate_noexcept): Keep going after
> > successfully synthesizing a DECL_MAYBE_DELETED fn.
> >
> > gcc/testsuite/ChangeLog:
> >
> > * g++.dg/cpp2a/spaceship-synth15.C: New test.
> > ---
> > gcc/cp/pt.cc | 3 ++-
> > .../g++.dg/cpp2a/spaceship-synth15.C | 22 +++++++++++++++++++
> > 2 files changed, 24 insertions(+), 1 deletion(-)
> > create mode 100644 gcc/testsuite/g++.dg/cpp2a/spaceship-synth15.C
> >
> > diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
> > index 6dd64101ced..03345ed3ed3 100644
> > --- a/gcc/cp/pt.cc
> > +++ b/gcc/cp/pt.cc
> > @@ -25986,7 +25986,8 @@ maybe_instantiate_noexcept (tree fn, tsubst_flags_t
> > complain)
> > ++function_depth;
> > maybe_synthesize_method (fn);
> > --function_depth;
> > - return !DECL_MAYBE_DELETED (fn);
> > + if (DECL_MAYBE_DELETED (fn))
> > + return false;
> > }
> > tree fntype = TREE_TYPE (fn);
> > diff --git a/gcc/testsuite/g++.dg/cpp2a/spaceship-synth15.C
> > b/gcc/testsuite/g++.dg/cpp2a/spaceship-synth15.C
> > new file mode 100644
> > index 00000000000..00ea6c10474
> > --- /dev/null
> > +++ b/gcc/testsuite/g++.dg/cpp2a/spaceship-synth15.C
> > @@ -0,0 +1,22 @@
> > +// PR c++/96242
> > +// { dg-do compile { target c++20 } }
> > +
> > +#include <compare>
> > +
> > +template<bool B>
> > +struct X {
> > + auto operator<=>(const X&) const noexcept(B) = default;
> > + bool operator==(const X&) const noexcept(!B) = default;
> > +};
> > +
> > +X<true> x_t;
> > +static_assert(noexcept(x_t <=> x_t));
> > +static_assert(noexcept(x_t < x_t));
> > +static_assert(!noexcept(x_t == x_t));
> > +static_assert(!noexcept(x_t != x_t));
> > +
> > +X<false> x_f;
> > +static_assert(!noexcept(x_f <=> x_f));
> > +static_assert(!noexcept(x_f < x_f));
> > +static_assert(noexcept(x_f == x_f));
> > +static_assert(noexcept(x_f != x_f));
>
>
