[Bug c++/99040] New: [modules] partitions & using declarations

[Bug c++/99040] New: [modules] partitions & using declarations

[nathan at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99040

            Bug ID: 99040
           Summary: [modules] partitions & using declarations
           Product: gcc
           Version: 11.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: nathan at gcc dot gnu.org
  Target Milestone: ---

triaged from pr98760

// t1.ii
export  module  format;

export namespace NS
{
void Format ();
}

// t2.ii
export  module  hello:check;

export namespace NS {}

// t3.ii
export  module  hello;
export import :check;
import  format;

export namespace NS
{
using NS::Format;
}

// t4.ii
module  hello;

./cc1plus -quiet -std=c++17 -fmodules-ts -fpreprocessed t1.ii && ./cc1plus
-quiet -std=c++17 -fmodules-ts -fpreprocessed t2.ii && ./cc1plus -quiet
-std=c++17 -fmodules-ts -fpreprocessed t3.ii && ./cc1plus -quiet -std=c++17
-fmodules-ts -fpreprocessed t4.ii -fno-module-lazy
t4.ii:1:14: internal compiler error: in add_module_decl, at
cp/name-lookup.c:4199
    1 | module  hello;
      |              ^
0xd3c3ae add_module_decl(tree_node*, tree_node*, tree_node*)
        ../../../src/gcc/cp/name-lookup.c:4199
0xd0a848 module_state::read_cluster(unsigned int)
        ../../../src/gcc/cp/module.cc:14908
0xd13cf8 module_state::load_section(unsigned int, binding_slot*)
        ../../../src/gcc/cp/module.cc:18068
0xd13a26 module_state::read_language(bool)
        ../../../src/gcc/cp/module.cc:17997
0xd16625 direct_import
        ../../../src/gcc/cp/module.cc:18870
0xd16a79 declare_module(module_state*, unsigned int, bool, tree_node*,
cpp_reader*)
        ../../../src/gcc/cp/module.cc:18975
0xd72cf2 cp_parser_module_declaration
        ../../../src/gcc/cp/parser.c:13757
0xd5f315 cp_parser_translation_unit
        ../../../src/gcc/cp/parser.c:4894
0xdc21a4 c_parse_file()
        ../../../src/gcc/cp/parser.c:45179
0xfa7278 c_common_parse_file()
        ../../../src/gcc/c-family/c-opts.c:1218
Please submit a full bug report,
with preprocessed source if appropriate.
Please include the complete backtrace with any bug report.
See <https://gcc.gnu.org/bugs/> for instructions.

[Bug c++/99040] [modules] partitions & using declarations

[nathan at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99040

Nathan Sidwell <nathan at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
     Ever confirmed|0                           |1
           Assignee|unassigned at gcc dot gnu.org      |nathan at gcc dot gnu.org
             Status|UNCONFIRMED                 |ASSIGNED
   Last reconfirmed|                            |2021-02-10

[Bug c++/99040] [modules] partitions & using declarations

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99040

--- Comment #1 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Nathan Sidwell <nathan@gcc.gnu.org>:

https://gcc.gnu.org/g:8f93e1b892850b00bf6b9cbc5711a7d5bc367967

commit r11-7228-g8f93e1b892850b00bf6b9cbc5711a7d5bc367967
Author: Nathan Sidwell <nathan@acm.org>
Date:   Thu Feb 11 13:06:03 2021 -0800

    Expunge namespace-scope IDENTIFIER_TYPE_VALUE & global_type_name [PR 99039]

    IDENTIFIER_TYPE_VALUE and friends is a remnant of G++'s C origins.  It
    holds elaborated types on identifier-nodes.  While this is fine for C
    and for local and class-scopes in C++, it fails badly for namespaces.
    In that case a marker 'global_type_node' was used, which essentially
    signified 'this is a namespace-scope type *somewhere*', and you'd have
    to do a regular name_lookup to find it.  As the parser and
    substitution machinery has avanced over the last 25 years or so,
    there's not much outside of actual name-lookup that uses that.
    Amusingly the IDENTIFIER_HAS_TYPE_VALUE predicate will do an actual
    name-lookup and then users would repeat that lookup to find the
    now-known to be there type.

    Rather late I realized that this interferes with the lazy loading of
    module entities, because we were setting IDENTIFIER_TYPE_VALUE to
    global_type_node.  But we could be inside some local scope where that
    identifier is bound to some local type.  Not good!

    Rather than add more cruft to look at an identifier's shadow stack and
    alter that as necessary, this takes the approach of removing the
    existing cruft.

    We nuke the few places outside of name lookup that use
    IDENTIFIER_TYPE_VALUE.  Replacing them with either proper name
    lookups, alternative sequences, or in some cases asserting that they
    (no longer) happen.  Class template instantiation was calling pushtag
    after setting IDENTIFIER_TYPE_VALUE in order to stop pushtag creating
    an implicit typedef and pushing it, but to get the bookkeeping it
    needed.  Let's just do the bookkeeping directly.

    Then we can stop having a 'bound at namespace-scope' marker at all,
    which means lazy loading won't screw up local shadow stacks.  Also, it
    simplifies set_identifier_type_value_with_scope, as it never needs to
    inspect the scope stack.  When developing this patch, I discovered a
    number of places we'd put an actual namespace-scope type on the
    type_value slot, rather than global_type_node.  You might notice this
    is killing at least two 'why are we doing this?' comments.

    While this doesn't fix the two PRs mentioned, it is a necessary step.

            PR c++/99039
            PR c++/99040
            gcc/cp/
            * cp-tree.h (CPTI_GLOBAL_TYPE): Delete.
            (global_type_node): Delete.
            (IDENTIFIER_TYPE_VALUE): Delete.
            (IDENTIFIER_HAS_TYPE_VALUE): Delete.
            (get_type_value): Delete.
            * name-lookup.h (identifier_type_value): Delete.
            * name-lookup.c (check_module_override): Don't
            SET_IDENTIFIER_TYPE_VALUE here.
            (do_pushdecl): Nor here.
            (identifier_type_value_1, identifier_type_value): Delete.
            (set_identifier_type_value_with_scope): Only
            SET_IDENTIFIER_TYPE_VALUE for local and class scopes.
            (pushdecl_nanmespace_level): Remove shadow stack nadgering.
            (do_pushtag): Use REAL_IDENTIFIER_TYPE_VALUE.
            * call.c (check_dtor_name): Use lookup_name.
            * decl.c (cxx_init_decl_processing): Drop global_type_node.
            * decl2.c (cplus_decl_attributes): Don't SET_IDENTIFIER_TYPE_VALUE
            here.
            * init.c (get_type_value): Delete.
            * pt.c (instantiate_class_template_1): Don't call pushtag or
            SET_IDENTIFIER_TYPE_VALUE here.
            (tsubst): Assert never an identifier.
            (dependent_type_p): Drop global_type_node assert.
            * typeck.c (error_args_num): Don't use IDENTIFIER_HAS_TYPE_VALUE
            to determine ctorness.
            gcc/testsuite/
            * g++.dg/lookup/pr99039.C: New.

[Bug c++/99040] [modules] partitions & using declarations

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99040

--- Comment #2 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Nathan Sidwell <nathan@gcc.gnu.org>:

https://gcc.gnu.org/g:0c27fe96f812df76ca07272d3c68765bd1f9dc08

commit r11-7229-g0c27fe96f812df76ca07272d3c68765bd1f9dc08
Author: Nathan Sidwell <nathan@acm.org>
Date:   Fri Feb 12 06:55:49 2021 -0800

    c++: Register streamed-in decls when new [PR 99040]

    With modules one can have using-decls refering to their own scope.  This
    is the way to export things from the GMF or from an import.  The
    problem was I was using current_ns == CP_DECL_CONTEXT (decl) to
    determine whether a decl should be registered in a namespace level or
    not.  But that's an inadequate check and we ended up reregistering
    decls and creating a circular list.  We should be registering the decl
    when first encountered -- whether we bind it is orthogonal to that.

            PR c++/99040
            gcc/cp/
            * module.cc (trees_in::decl_value): Call add_module_namespace_decl
            for new namespace-scope entities.
            (module_state::read_cluster): Don't call add_module_decl here.
            * name-lookup.h (add_module_decl): Rename to ...
            (add_module_namespace_decl): ... this.
            * name-lookup.c (newbinding_bookkeeping): Move into ...
            (do_pushdecl): ... here.  Its only remaining caller.
            (add_module_decl): Rename to ...
            (add_module_namespace_decl): ... here.  Add checking-assert for
            circularity. Don't call newbinding_bookkeeping, just extern_c
            checking and incomplete var checking.
            gcc/testsuite/
            * g++.dg/modules/pr99040_a.C: New.
            * g++.dg/modules/pr99040_b.C: New.
            * g++.dg/modules/pr99040_c.C: New.
            * g++.dg/modules/pr99040_d.C: New.

[Bug c++/99040] [modules] partitions & using declarations

[nathan at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99040

Nathan Sidwell <nathan at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |FIXED
             Status|ASSIGNED                    |RESOLVED

--- Comment #3 from Nathan Sidwell <nathan at gcc dot gnu.org> ---
0c27fe96f81 2021-02-12 | c++: Register streamed-in decls when new [PR 99040]