On Fri, 1 Oct 2021, Patrick Palka wrote:
> On Fri, Oct 1, 2021 at 1:29 PM Patrick Palka <[email protected]> wrote:
> >
> > On Fri, 1 Oct 2021, Jason Merrill wrote:
> >
> > > On 10/1/21 10:26, Patrick Palka wrote:
> > > > On Fri, 1 Oct 2021, Jason Merrill wrote:
> > > >
> > > > > On 10/1/21 09:46, Patrick Palka wrote:
> > > > > > Here during partial ordering of the two partial specializations we
> > > > > > end
> > > > > > up in unify with parm=arg=NONTYPE_ARGUMENT_PACK<V0, V1>, and crash
> > > > > > shortly
> > > > > > thereafter because uses_template_parms calls
> > > > > > potential_constant_expression
> > > > > > which doesn't handle NONTYPE_ARGUMENT_PACK.
> > > > > >
> > > > > > This patch fixes this by checking dependent_template_arg_p instead
> > > > > > of
> > > > > > uses_template_parms when parm==arg, which does handle
> > > > > > NONTYPE_ARGUMENT_PACK.
> > > > > > We could also perhaps fix uses_template_parms / inst_dep_expr_p to
> > > > > > better
> > > > > > handle NONTYPE_ARGUMENT_PACK,
> > > > >
> > > > > Please.
> > > >
> > > > Sounds good, like the following then? Passes light testing, bootstrap
> > > > and regtest on progress.
> > > >
> > > > -- >8 --
> > > >
> > > > PR c++/102547
> > > >
> > > > gcc/cp/ChangeLog:
> > > >
> > > > * pt.c (instantiation_dependent_expression_p): Sidestep checking
> > > > potential_constant_expression on NONTYPE_ARGUMENT_PACK.
> > > >
> > > > gcc/testsuite/ChangeLog:
> > > >
> > > > * g++.dg/cpp0x/variadic-partial2.C: New test.
> > > > * g++.dg/cpp0x/variadic-partial2a.C: New test.
> > > > ---
> > > > gcc/cp/pt.c | 4 +++-
> > > > .../g++.dg/cpp0x/variadic-partial2.C | 16 ++++++++++++++
> > > > .../g++.dg/cpp0x/variadic-partial2a.C | 22 +++++++++++++++++++
> > > > 3 files changed, 41 insertions(+), 1 deletion(-)
> > > > create mode 100644 gcc/testsuite/g++.dg/cpp0x/variadic-partial2.C
> > > > create mode 100644 gcc/testsuite/g++.dg/cpp0x/variadic-partial2a.C
> > > >
> > > > diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
> > > > index 1dcdffe322a..643204103c5 100644
> > > > --- a/gcc/cp/pt.c
> > > > +++ b/gcc/cp/pt.c
> > > > @@ -27705,7 +27705,9 @@ instantiation_dependent_expression_p (tree
> > > > expression)
> > > > {
> > > > return (instantiation_dependent_uneval_expression_p (expression)
> > > > || (processing_template_decl
> > > > - && potential_constant_expression (expression)
> > > > + && expression != NULL_TREE
> > > > + && (TREE_CODE (expression) == NONTYPE_ARGUMENT_PACK
> > > > + || potential_constant_expression (expression))
> > >
> > > I'd prefer to loop over the elements of the pack, either here or (probably
> > > better) in potential_constant_expression.
> >
> > Ah, makes sense. Like so? Bootstrapped and regtested on
> > x86_64-pc-linux-gnu.
>
> On second thought given that a NONTYPE_ARGUMENT_PACK is by
> construction a sequence of non-type template arguments, is looping
> over its elements in potential_const_expr necessary? Maybe we should
> just return true unconditionally.
Never mind, I forgot that we also use NONTYPE_ARGUMENT_PACK to pack
function arguments, so we can't just assume the elements are always
constant.
>
> >
> > -- >8 --
> >
> > Subject: [PATCH] c++: unifying equal NONTYPE_ARGUMENT_PACKs [PR102547]
> >
> > Here during partial ordering of the two partial specializations we end
> > up in unify with parm=arg=NONTYPE_ARGUMENT_PACK<V0, V1>, and crash shortly
> > thereafter because uses_template_parms(parms) calls potential_const_expr
> > which doesn't handle NONTYPE_ARGUMENT_PACK.
> >
> > This patch fixes this by extending potential_constant_expression to handle
> > NONTYPE_ARGUMENT_PACK appropriately.
> >
> > Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for
> > trunk/11?
> >
> > PR c++/102547
> >
> > gcc/cp/ChangeLog:
> >
> > * constexpr.c (potential_constant_expression_1): Handle
> > NONTYPE_ARGUMENT_PACK.
> >
> > gcc/testsuite/ChangeLog:
> >
> > * g++.dg/cpp0x/variadic-partial2.C: New test.
> > * g++.dg/cpp0x/variadic-partial2a.C: New test.
> > ---
> > gcc/cp/constexpr.c | 10 +++++++++
> > .../g++.dg/cpp0x/variadic-partial2.C | 16 ++++++++++++++
> > .../g++.dg/cpp0x/variadic-partial2a.C | 22 +++++++++++++++++++
> > 3 files changed, 48 insertions(+)
> > create mode 100644 gcc/testsuite/g++.dg/cpp0x/variadic-partial2.C
> > create mode 100644 gcc/testsuite/g++.dg/cpp0x/variadic-partial2a.C
> >
> > diff --git a/gcc/cp/constexpr.c b/gcc/cp/constexpr.c
> > index 18d9d117a48..e95ff00774f 100644
> > --- a/gcc/cp/constexpr.c
> > +++ b/gcc/cp/constexpr.c
> > @@ -9043,6 +9043,16 @@ potential_constant_expression_1 (tree t, bool
> > want_rval, bool strict, bool now,
> > case CO_RETURN_EXPR:
> > return false;
> >
> > + case NONTYPE_ARGUMENT_PACK:
> > + {
> > + tree args = ARGUMENT_PACK_ARGS (t);
> > + int len = TREE_VEC_LENGTH (args);
> > + for (int i = 0; i < len; ++i)
> > + if (!RECUR (TREE_VEC_ELT (args, i), any))
> > + return false;
> > + return true;
> > + }
> > +
> > default:
> > if (objc_non_constant_expr_p (t))
> > return false;
> > diff --git a/gcc/testsuite/g++.dg/cpp0x/variadic-partial2.C
> > b/gcc/testsuite/g++.dg/cpp0x/variadic-partial2.C
> > new file mode 100644
> > index 00000000000..df61f26a3c1
> > --- /dev/null
> > +++ b/gcc/testsuite/g++.dg/cpp0x/variadic-partial2.C
> > @@ -0,0 +1,16 @@
> > +// PR c++/102547
> > +// { dg-do compile { target c++11 } }
> > +
> > +template<int... Vs>
> > +struct vals { };
> > +
> > +template<class V, class T>
> > +struct vals_client { };
> > +
> > +template<int V0, int V1, class T>
> > +struct vals_client<vals<V0, V1>, T> { };
> > +
> > +template<int V0, int V1>
> > +struct vals_client<vals<V0, V1>, void> { };
> > +
> > +template struct vals_client<vals<1, 2>, void>; //- "sorry,
> > unimplemented..., ICE"
> > diff --git a/gcc/testsuite/g++.dg/cpp0x/variadic-partial2a.C
> > b/gcc/testsuite/g++.dg/cpp0x/variadic-partial2a.C
> > new file mode 100644
> > index 00000000000..e98bdbbc07b
> > --- /dev/null
> > +++ b/gcc/testsuite/g++.dg/cpp0x/variadic-partial2a.C
> > @@ -0,0 +1,22 @@
> > +// PR c++/102547
> > +// { dg-do compile { target c++11 } }
> > +// A version of variadic-partial2.C where partial ordering is performed
> > +// on function templates instead of class templates.
> > +
> > +template<int... Vs>
> > +struct vals { };
> > +
> > +template<class V, class T>
> > +void f(V, T) { };
> > +
> > +template<int V0, int V1, class T>
> > +void f(vals<V0, V1>, T) { };
> > +
> > +template<int V0, int V1>
> > +void f(vals<V0, V1>, char) { };
> > +
> > +template void f(vals<1, 2>, char); //- "sorry, unimplemented..., ICE"
> > +
> > +int main() {
> > + f(vals<1, 3>{}, 'a'); //- "sorry, unimplemented..., ICE"
> > +}
> > --
> > 2.33.0.610.gcefe983a32
> >
>
