Re: C++ PATCH to implement P1094R2, Nested inline namespaces

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

On Mon, Nov 19, 2018 at 11:12 PM Marek Polacek <polacek@redhat.com> wrote:
>
> On Mon, Nov 19, 2018 at 10:33:17PM +0100, Jakub Jelinek wrote:
> > On Mon, Nov 19, 2018 at 04:21:19PM -0500, Marek Polacek wrote:
> > > 2018-11-19  Marek Polacek  <polacek@redhat.com>
> > >
> > >     Implement P1094R2, Nested inline namespaces.
> > >     * g++.dg/cpp2a/nested-inline-ns1.C: New test.
> > >     * g++.dg/cpp2a/nested-inline-ns2.C: New test.
> > >     * g++.dg/cpp2a/nested-inline-ns3.C: New test.
> >
> > Just a small testsuite comment.
> >
> > > --- /dev/null
> > > +++ gcc/testsuite/g++.dg/cpp2a/nested-inline-ns1.C
> > > @@ -0,0 +1,26 @@
> > > +// P1094R2
> > > +// { dg-do compile { target c++2a } }
> >
> > Especially because 2a testing isn't included by default, but also
> > to make sure it works right even with -std=c++17, wouldn't it be better to
> > drop the nested-inline-ns3.C test, make this test c++17 or
> > even better always enabled, add dg-options "-Wpedantic" and
> > just add dg-warning with c++17_down and c++14_down what should be
> > warned on the 3 lines (with .-1 for c++14_down)?
> >
> > Or if you want add some further testcases that will test how
> > c++17 etc. will dg-error on those with -pedantic-errors etc.
>
> Sure, I've made it { target c++11 } and dropped the third test:
>
> Bootstrapped/regtested on x86_64-linux, ok for trunk?

Just another small comment - given the usual high number of
C++ regressions delaying the release is Stage3 the right time
to add new language features?

> 2018-11-19  Marek Polacek  <polacek@redhat.com>
>
>         Implement P1094R2, Nested inline namespaces.
>         * parser.c (cp_parser_namespace_definition): Parse the optional inline
>         keyword in a nested-namespace-definition.  Adjust push_namespace call.
>         Formatting fix.
>
>         * g++.dg/cpp2a/nested-inline-ns1.C: New test.
>         * g++.dg/cpp2a/nested-inline-ns2.C: New test.
>
> diff --git gcc/cp/parser.c gcc/cp/parser.c
> index 292cce15676..f39e9d753d2 100644
> --- gcc/cp/parser.c
> +++ gcc/cp/parser.c
> @@ -18872,6 +18872,7 @@ cp_parser_namespace_definition (cp_parser* parser)
>    cp_ensure_no_oacc_routine (parser);
>
>    bool is_inline = cp_lexer_next_token_is_keyword (parser->lexer, RID_INLINE);
> +  const bool topmost_inline_p = is_inline;
>
>    if (is_inline)
>      {
> @@ -18890,6 +18891,17 @@ cp_parser_namespace_definition (cp_parser* parser)
>      {
>        identifier = NULL_TREE;
>
> +      bool nested_inline_p = cp_lexer_next_token_is_keyword (parser->lexer,
> +                                                            RID_INLINE);
> +      if (nested_inline_p && nested_definition_count != 0)
> +       {
> +         if (cxx_dialect < cxx2a)
> +           pedwarn (cp_lexer_peek_token (parser->lexer)->location,
> +                    OPT_Wpedantic, "nested inline namespace definitions only "
> +                    "available with -std=c++2a or -std=gnu++2a");
> +         cp_lexer_consume_token (parser->lexer);
> +       }
> +
>        if (cp_lexer_next_token_is (parser->lexer, CPP_NAME))
>         {
>           identifier = cp_parser_identifier (parser);
> @@ -18904,7 +18916,12 @@ cp_parser_namespace_definition (cp_parser* parser)
>         }
>
>        if (cp_lexer_next_token_is_not (parser->lexer, CPP_SCOPE))
> -       break;
> +       {
> +         /* Don't forget that the innermost namespace might have been
> +            marked as inline.  */
> +         is_inline |= nested_inline_p;
> +         break;
> +       }
>
>        if (!nested_definition_count && cxx_dialect < cxx17)
>          pedwarn (input_location, OPT_Wpedantic,
> @@ -18913,7 +18930,9 @@ cp_parser_namespace_definition (cp_parser* parser)
>
>        /* Nested namespace names can create new namespaces (unlike
>          other qualified-ids).  */
> -      if (int count = identifier ? push_namespace (identifier) : 0)
> +      if (int count = (identifier
> +                      ? push_namespace (identifier, nested_inline_p)
> +                      : 0))
>         nested_definition_count += count;
>        else
>         cp_parser_error (parser, "nested namespace name required");
> @@ -18926,7 +18945,7 @@ cp_parser_namespace_definition (cp_parser* parser)
>    if (nested_definition_count && attribs)
>      error_at (token->location,
>               "a nested namespace definition cannot have attributes");
> -  if (nested_definition_count && is_inline)
> +  if (nested_definition_count && topmost_inline_p)
>      error_at (token->location,
>               "a nested namespace definition cannot be inline");
>
> @@ -18935,7 +18954,7 @@ cp_parser_namespace_definition (cp_parser* parser)
>
>    bool has_visibility = handle_namespace_attrs (current_namespace, attribs);
>
> -  warning  (OPT_Wnamespaces, "namespace %qD entered", current_namespace);
> +  warning (OPT_Wnamespaces, "namespace %qD entered", current_namespace);
>
>    /* Look for the `{' to validate starting the namespace.  */
>    matching_braces braces;
> diff --git gcc/testsuite/g++.dg/cpp2a/nested-inline-ns1.C gcc/testsuite/g++.dg/cpp2a/nested-inline-ns1.C
> new file mode 100644
> index 00000000000..8c9573ea5db
> --- /dev/null
> +++ gcc/testsuite/g++.dg/cpp2a/nested-inline-ns1.C
> @@ -0,0 +1,29 @@
> +// P1094R2
> +// { dg-do compile { target c++11 } }
> +// { dg-options "-Wpedantic" }
> +
> +namespace A::inline B::C { // { dg-warning "nested inline namespace definitions only" "" { target c++17_down } }
> +// { dg-warning "nested namespace definitions only available" "" { target c++14_down } .-1 }
> +  int i;
> +}
> +
> +namespace D::E::inline F { // { dg-warning "nested inline namespace definitions only" "" { target c++17_down } }
> +// { dg-warning "nested namespace definitions only available" "" { target c++14_down } .-1 }
> +  int j;
> +}
> +
> +inline namespace X {
> +  int x;
> +}
> +
> +// Make sure the namespaces are marked inline.
> +void
> +g ()
> +{
> +  A::B::C::i++;
> +  A::C::i++;
> +  D::E::j++;
> +  D::E::F::j++;
> +  X::x++;
> +  x++;
> +}
> diff --git gcc/testsuite/g++.dg/cpp2a/nested-inline-ns2.C gcc/testsuite/g++.dg/cpp2a/nested-inline-ns2.C
> new file mode 100644
> index 00000000000..9b5f2cab47b
> --- /dev/null
> +++ gcc/testsuite/g++.dg/cpp2a/nested-inline-ns2.C
> @@ -0,0 +1,26 @@
> +// P1094R2
> +// { dg-do compile { target c++2a } }
> +
> +inline namespace A::B { // { dg-error "a nested namespace definition cannot be inline" }
> +  int i;
> +}
> +
> +namespace inline C::D { // { dg-error "expected|does not name a type" }
> +  int i;
> +}
> +
> +namespace E::F inline { // { dg-error "expected" }
> +  int i;
> +}
> +
> +namespace inline G { // { dg-error "expected|does not name a type" }
> +  int i;
> +}
> +
> +inline namespace inline H { // { dg-error "expected|does not name a type" }
> +  int i;
> +}
> +
> +inline namespace inline I::J { // { dg-error "expected|does not name a type" }
> +  int i;
> +}