On Thu, Jul 20, 2023 at 02:37:07PM -0400, Jason Merrill wrote:
> On 7/20/23 14:13, Marek Polacek wrote:
> > On Wed, Jul 19, 2023 at 10:11:27AM -0400, Patrick Palka wrote:
> > > On Tue, 18 Jul 2023, Marek Polacek via Gcc-patches wrote:
> > >
> > > > Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk and
> > > > branches?
> > >
> > > Looks reasonable to me.
> >
> > Thanks.
> > > Though I wonder if we could also fix this by not checking potentiality
> > > at all in this case? The problematic call to
> > > is_rvalue_constant_expression
> > > happens from cp_parser_constant_expression with 'allow_non_constant' != 0
> > > and with 'non_constant_p' being a dummy out argument that comes from
> > > cp_parser_functional_cast, so the result of is_rvalue_constant_expression
> > > is effectively unused in this case, and we should be able to safely elide
> > > it when 'allow_non_constant && non_constant_p == nullptr'.
> >
> > Sounds plausible. I think my patch could be applied first since it
> > removes a tiny bit of code, then I can hopefully remove the flag below,
> > then maybe go back and optimize the call to is_rvalue_constant_expression.
> > Does that sound sensible?
> >
> > > Relatedly, ISTM the member cp_parser::non_integral_constant_expression_p
> > > is also effectively unused and could be removed?
> >
> > It looks that way. Seems it's only used in cp_parser_constant_expression:
> > 10806 if (allow_non_constant_p)
> > 10807 *non_constant_p = parser->non_integral_constant_expression_p;
> > but that could be easily replaced by a local var. I'd be happy to see if
> > we can actually do away with it. (I wonder why it was introduced and when
> > it actually stopped being useful.)
>
> It was for the C++98 notion of constant-expression, which was more of a
> parser-level notion, and has been supplanted by the C++11 version. I'm
> happy to remove it, and therefore remove the is_rvalue_constant_expression
> call.
Wonderful. I'll do that next.
> > > > -- >8 --
> > > >
> > > > is_really_empty_class is liable to crash when it gets an incomplete
> > > > or dependent type. Since r11-557, we pass the yet-uninstantiated
> > > > class type S<0> of the PARM_DECL s to is_really_empty_class -- because
> > > > of the potential_rvalue_constant_expression ->
> > > > is_rvalue_constant_expression
> > > > change in cp_parser_constant_expression. Here we're not parsing
> > > > a template so we did not check COMPLETE_TYPE_P as we should.
> > > >
> > > > PR c++/110106
> > > >
> > > > gcc/cp/ChangeLog:
> > > >
> > > > * constexpr.cc (potential_constant_expression_1): Check
> > > > COMPLETE_TYPE_P
> > > > even when !processing_template_decl.
> > > >
> > > > gcc/testsuite/ChangeLog:
> > > >
> > > > * g++.dg/cpp0x/noexcept80.C: New test.
> > > > ---
> > > > gcc/cp/constexpr.cc | 2 +-
> > > > gcc/testsuite/g++.dg/cpp0x/noexcept80.C | 12 ++++++++++++
> > > > 2 files changed, 13 insertions(+), 1 deletion(-)
> > > > create mode 100644 gcc/testsuite/g++.dg/cpp0x/noexcept80.C
> > > >
> > > > diff --git a/gcc/cp/constexpr.cc b/gcc/cp/constexpr.cc
> > > > index 6e8f1c2b61e..1f59c5472fb 100644
> > > > --- a/gcc/cp/constexpr.cc
> > > > +++ b/gcc/cp/constexpr.cc
> > > > @@ -9116,7 +9116,7 @@ potential_constant_expression_1 (tree t, bool
> > > > want_rval, bool strict, bool now,
> > > > if (now && want_rval)
> > > > {
> > > > tree type = TREE_TYPE (t);
> > > > - if ((processing_template_decl && !COMPLETE_TYPE_P (type))
> > > > + if (!COMPLETE_TYPE_P (type)
> > > > || dependent_type_p (type)
>
> There shouldn't be a problem completing the type here, so it seems to me
> that we're missing a call to complete_type_p, at least when
> !processing_template_decl. Probably need to move the dependent_type_p check
> up as a result.
Like so?
Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
-- >8 --
is_really_empty_class is liable to crash when it gets an incomplete
or dependent type. Since r11-557, we pass the yet-uninstantiated
class type S<0> of the PARM_DECL s to is_really_empty_class -- because
of the potential_rvalue_constant_expression -> is_rvalue_constant_expression
change in cp_parser_constant_expression. Here we're not parsing
a template so we did not check COMPLETE_TYPE_P as we should.
It should work to complete the type before checking COMPLETE_TYPE_P.
PR c++/110106
gcc/cp/ChangeLog:
* constexpr.cc (potential_constant_expression_1): Try to complete the
type when !processing_template_decl.
gcc/testsuite/ChangeLog:
* g++.dg/cpp0x/noexcept80.C: New test.
---
gcc/cp/constexpr.cc | 5 +++--
gcc/testsuite/g++.dg/cpp0x/noexcept80.C | 12 ++++++++++++
2 files changed, 15 insertions(+), 2 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/cpp0x/noexcept80.C
diff --git a/gcc/cp/constexpr.cc b/gcc/cp/constexpr.cc
index 6e8f1c2b61e..fb94f3cefcb 100644
--- a/gcc/cp/constexpr.cc
+++ b/gcc/cp/constexpr.cc
@@ -9116,8 +9116,9 @@ potential_constant_expression_1 (tree t, bool want_rval,
bool strict, bool now,
if (now && want_rval)
{
tree type = TREE_TYPE (t);
- if ((processing_template_decl && !COMPLETE_TYPE_P (type))
- || dependent_type_p (type)
+ if (dependent_type_p (type)
+ || !COMPLETE_TYPE_P (processing_template_decl
+ ? type : complete_type (type))
|| is_really_empty_class (type, /*ignore_vptr*/false))
/* An empty class has no data to read. */
return true;
diff --git a/gcc/testsuite/g++.dg/cpp0x/noexcept80.C
b/gcc/testsuite/g++.dg/cpp0x/noexcept80.C
new file mode 100644
index 00000000000..3e90af747e2
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/noexcept80.C
@@ -0,0 +1,12 @@
+// PR c++/110106
+// { dg-do compile { target c++11 } }
+
+template<int> struct S
+{
+};
+
+struct G {
+ G(S<0>);
+};
+
+void y(S<0> s) noexcept(noexcept(G{s}));
base-commit: 4b8878fbf7b74ea5c3405c9f558df0517036f131
--
2.41.0
