On Mon, Jan 27, 2025 at 10:20:05AM -0500, Patrick Palka wrote:
> On Sat, 12 Oct 2024, Nathaniel Shead wrote:
>
> > This version rewords all "ignored exposures" language.
> >
> > I haven't fixed up the issue with DECL_TEMPLATE_INSTANTIATIONS for this
> > patch. I'll try to get to that as a separate patch if I find the time,
> > but it's not 100% needed here I don't think.
> >
> > It seems the discussion around PR115126 RE: the libgcc changes that
> > people are leaning towards reverting the changes I made to the gthread
> > static variables and instead having some sort of attribute to instruct
> > the compiler to ignore the ODR issues; that should be relatively
> > straight-forward to add (maybe something like [[gnu::ignore_tu_local]]?)
> > but I'll probably handle that as a separate patch once I'm sure that's
> > what we actually want to do, and would probably be worth corresponding
> > with the Clang folks to see what thoughts they have.
> >
> > Finally, I wasn't able to work out a good way to fold non-ODR usages of
> > TU-local constants early. I attempted modifying 'mark_use', which
> > helped for 'constexpr' usages (though I ran into issues with e.g.
> >
> > constexpr int n[1] = 0;
> > constexpr int x = n ? 1 : 2;
> >
> > segfaulting as build_address was not expecting to see a constructor
> > rather than a declaration here). But I didn't look too hard into
> > solving this as it appears that any modifications made by 'mark_use' are
> > not actually applied to the primary template at all, and this is
> > consistent across many places I investigated.
> >
> > Given that erroring on these cases is still the status-quo, how easy it
> > is to workaround most of the time, and that I'm still not sure how to
> > solve this, I've also left this as a FIXME (with an XFAILed testcase) to
> > revisit later.
> >
> > OK for trunk?
> >
> > -- >8 --
> >
> > [basic.link] p14 lists a number of circumstances where a declaration
> > naming a TU-local entity is not an exposure, notably the bodies of
> > non-inline templates and friend declarations in classes. This patch
> > ensures that these references do not error when exporting the module.
> >
> > We do need to still error on instantiation from a different module,
> > however, in case this refers to a TU-local entity. As such this patch
> > adds a new tree TU_LOCAL_ENTITY which is used purely as a placeholder to
> > poison any attempted template instantiations that refer to it.
>
> I'm a bit late to the party, but this is a nice patch series! I have a
> couple of comments below.
>
> >
> > This is also streamed for friend decls so that merging (based on the
> > index of an entity into the friend decl list) doesn't break and to
> > prevent complicating the logic; I imagine this shouldn't ever come up
> > though.
> >
> > We also add a new warning, '-Wtemplate-names-tu-local', to handle the
> > case where someone accidentally refers to a TU-local value from within a
> > non-inline function template. This will compile without errors as-is,
> > but any attempt to instantiate the decl will fail; this warning can be
> > used to ensure that this doesn't happen. Unfortunately the warning has
> > quite some false positives; for instance, a user could deliberately only
> > call explicit instantiations of the decl, or use 'if constexpr' to avoid
> > instantiating the TU-local entity from other TUs, neither of which are
> > currently detected.
> >
> > The main piece that this patch doesn't yet attempt to solve is ADL: as
> > specified, if ADL adds an overload set that includes a translation-unit
> > local entity when instantiating a template, that overload set is now
> > poisoned and counts as an exposure. Unfortunately, we don't currently
> > differentiate between decls that are hidden due to not being exported,
> > or decls that are hidden due to being hidden friends, so this patch
> > instead just keeps the current (wrong) behaviour of non-exported
> > entities not being visible to ADL at all.
> >
> > Additionally, this patch doesn't attempt to ignore non-ODR uses of
> > constants in constexpr functions or templates. The obvious approach of
> > folding them early in 'mark_use' doesn't seem to work (for a variety of
> > reasons), so this leaves this to a later patch to implement, as it's at
> > least no worse than the current behaviour and easy enough to workaround.
> >
> > For completeness this patch adds a new xtreme-header testcase to ensure
> > that we have no regressions with regards to exposures of TU-local
> > declarations in the standard library header files. A more restrictive
> > test would be to do 'export extern "C++"' here, but unfortunately the
> > system headers on some targets declare TU-local entities, so we'll make
> > do with checking that at least the C++ standard library headers don't
> > refer to such entities.
> >
> > gcc/c-family/ChangeLog:
> >
> > * c.opt: New warning '-Wtemplate-names-tu-local'.
> >
> > gcc/cp/ChangeLog:
> >
> > * cp-objcp-common.cc (cp_tree_size): Add TU_LOCAL_ENTITY.
> > * cp-tree.def (TU_LOCAL_ENTITY): New tree code.
> > * cp-tree.h (struct tree_tu_local_entity): New type.
> > (TU_LOCAL_ENTITY_NAME): New accessor.
> > (TU_LOCAL_ENTITY_LOCATION): New accessor.
> > (enum cp_tree_node_structure_enum): Add TS_CP_TU_LOCAL_ENTITY.
> > (union GTY): Add tu_local_entity field.
> > * module.cc (enum tree_tag): New flag DB_REFS_TU_LOCAL_BIT.
> > (depset::has_defn): Override for TU-local entities.
> > (depset::refs_tu_local): New accessor.
> > (depset::hash::ignore_tu_local): New field.
> > (depset::hash::hash): Initialize it.
> > (trees_out::tree_tag::tt_tu_local): New flag.
> > (trees_out::writing_local_entities): New field.
> > (trees_out::is_initial_scan): New function.
> > (trees_out::tu_local_count): New counter.
> > (trees_out::trees_out): Initialize writing_local_entities.
> > (dumper::impl::nested_name): Handle TU_LOCAL_ENTITY.
> > (trees_out::instrument): Report TU-local entity counts.
> > (trees_out::decl_value): Early exit for TU-local entities.
> > (trees_in::decl_value): Handle typedefs of TU-local entities.
> > (trees_out::decl_node): Adjust assertion to cope with early exit
> > of TU-local deps. Always write TU-local entities by value.
> > (trees_out::type_node): Handle TU-local types.
> > (trees_out::has_tu_local_dep): New function.
> > (trees_out::find_tu_local_decl): New function.
> > (trees_out::tree_node): Intercept TU-local entities and write
> > placeholder values for them instead of normal streaming.
> > (trees_in::tree_node): Handle TU-local entities and TU-local
> > template results.
> > (trees_out::write_function_def): Ignore exposures in non-inline
> > function bodies.
> > (trees_out::write_var_def): Ignore exposures in initializers.
> > (trees_out::write_class_def): Ignore exposures in friend decls.
> > (trees_in::read_class_def): Skip TU-local friends.
> > (trees_out::write_definition): Record whether we're writing a
> > decl which refers to TU-local entities.
> > (depset::hash::add_dependency): Only mark as exposure if we're not
> > ignoring TU-local entities.
> > (depset::hash::find_dependencies): Use depset's own is_key_order
> > function rather than delegating via walker. Pass whether the
> > decl has ignored TU-local entities in its definition.
> > (depset::hash::finalize_dependencies): Implement new warning
> > Wtemplate-names-tu-local.
> > (module_state::intercluster_seed): Don't seed TU-local deps.
> > (module_state::write_cluster): Pass whether the decl has ignored
> > TU-local entities in its definition.
> > * pt.cc (complain_about_tu_local_entity): New function.
> > (expr_contains_tu_local_entity): New function.
> > (function_contains_tu_local_entity): New function.
> > (instantiate_class_template): Skip TU-local friends.
> > (tsubst_decl): Handle typedefs of TU-local entities.
> > (tsubst): Complain about TU-local entities.
> > (dependent_operand_p): Early exit for TU-local entities so we
> > don't attempt to constant-evaluate them.
> > (tsubst_expr): Detect and complain about TU-local entities.
> >
> > gcc/ChangeLog:
> >
> > * doc/invoke.texi: Document -Wtemplate-names-tu-local.
> >
> > gcc/testsuite/ChangeLog:
> >
> > * g++.dg/modules/internal-5_a.C: New test.
> > * g++.dg/modules/internal-5_b.C: New test.
> > * g++.dg/modules/internal-6.C: New test.
> > * g++.dg/modules/internal-7_a.C: New test.
> > * g++.dg/modules/internal-7_b.C: New test.
> > * g++.dg/modules/internal-8_a.C: New test.
> > * g++.dg/modules/xtreme-header-8.C: New test.
> >
> > Signed-off-by: Nathaniel Shead <[email protected]>
> > Reviewed-by: Jason Merrill <[email protected]>
> > ---
> > gcc/c-family/c.opt | 4 +
> > gcc/cp/cp-objcp-common.cc | 1 +
> > gcc/cp/cp-tree.def | 6 +
> > gcc/cp/cp-tree.h | 21 +-
> > gcc/cp/module.cc | 318 +++++++++++++++---
> > gcc/cp/pt.cc | 98 +++++-
> > gcc/doc/invoke.texi | 19 +-
> > gcc/testsuite/g++.dg/modules/internal-5_a.C | 110 ++++++
> > gcc/testsuite/g++.dg/modules/internal-5_b.C | 30 ++
> > gcc/testsuite/g++.dg/modules/internal-6.C | 24 ++
> > gcc/testsuite/g++.dg/modules/internal-7_a.C | 75 +++++
> > gcc/testsuite/g++.dg/modules/internal-7_b.C | 21 ++
> > gcc/testsuite/g++.dg/modules/internal-8_a.C | 35 ++
> > .../g++.dg/modules/xtreme-header-8.C | 8 +
> > 14 files changed, 721 insertions(+), 49 deletions(-)
> > create mode 100644 gcc/testsuite/g++.dg/modules/internal-5_a.C
> > create mode 100644 gcc/testsuite/g++.dg/modules/internal-5_b.C
> > create mode 100644 gcc/testsuite/g++.dg/modules/internal-6.C
> > create mode 100644 gcc/testsuite/g++.dg/modules/internal-7_a.C
> > create mode 100644 gcc/testsuite/g++.dg/modules/internal-7_b.C
> > create mode 100644 gcc/testsuite/g++.dg/modules/internal-8_a.C
> > create mode 100644 gcc/testsuite/g++.dg/modules/xtreme-header-8.C
> >
> > diff --git a/gcc/c-family/c.opt b/gcc/c-family/c.opt
> > index 9d1fccadbf9..6e5ddefd0e2 100644
> > --- a/gcc/c-family/c.opt
> > +++ b/gcc/c-family/c.opt
> > @@ -1450,6 +1450,10 @@ Wtemplate-id-cdtor
> > C++ ObjC++ Var(warn_template_id_cdtor) Warning
> > Warn about simple-template-id in a constructor or destructor.
> >
> > +Wtemplate-names-tu-local
> > +C++ ObjC++ Var(warn_template_names_tu_local) Warning EnabledBy(Wextra)
> > +Warn about templates naming TU-local entities in a module.
> > +
> > Wterminate
> > C++ ObjC++ Warning Var(warn_terminate) Init(1)
> > Warn if a throw expression will always result in a call to terminate().
> > diff --git a/gcc/cp/cp-objcp-common.cc b/gcc/cp/cp-objcp-common.cc
> > index cd379514991..b959533bcb1 100644
> > --- a/gcc/cp/cp-objcp-common.cc
> > +++ b/gcc/cp/cp-objcp-common.cc
> > @@ -233,6 +233,7 @@ cp_tree_size (enum tree_code code)
> > case ASSERTION_STMT: return sizeof (tree_exp);
> > case PRECONDITION_STMT: return sizeof (tree_exp);
> > case POSTCONDITION_STMT: return sizeof (tree_exp);
> > + case TU_LOCAL_ENTITY: return sizeof (tree_tu_local_entity);
> > default:
> > switch (TREE_CODE_CLASS (code))
> > {
> > diff --git a/gcc/cp/cp-tree.def b/gcc/cp/cp-tree.def
> > index 18f75108c7b..7580dc3667d 100644
> > --- a/gcc/cp/cp-tree.def
> > +++ b/gcc/cp/cp-tree.def
> > @@ -573,6 +573,12 @@ DEFTREECODE (ASSERTION_STMT, "assertion_stmt",
> > tcc_statement, 3)
> > DEFTREECODE (PRECONDITION_STMT, "precondition_stmt", tcc_statement, 3)
> > DEFTREECODE (POSTCONDITION_STMT, "postcondition_stmt", tcc_statement, 4)
> >
> > +/* A reference to a translation-unit local entity.
> > +
> > + This is emitted by modules streaming when writing a TU-local entity that
> > + wasn't an exposure (e.g. in a non-inline function template). */
> > +DEFTREECODE (TU_LOCAL_ENTITY, "tu_local_entity", tcc_exceptional, 0)
> > +
> > /*
> > Local variables:
> > mode:c
> > diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
> > index dc153a97dc4..a71d0704f8b 100644
> > --- a/gcc/cp/cp-tree.h
> > +++ b/gcc/cp/cp-tree.h
> > @@ -1778,6 +1778,22 @@ check_constraint_info (tree t)
> > it for unscoped enums. */
> > #define DECL_MODULE_EXPORT_P(NODE) TREE_LANG_FLAG_3 (NODE)
> >
> > +/* Represents a streamed-in translation-unit-local entity. Any use of
> > + this node when instantiating a template should emit an error. */
> > +struct GTY(()) tree_tu_local_entity {
> > + struct tree_base base;
> > + tree name;
> > + location_t loc;
> > +};
> > +
> > +/* The name of a translation-unit-local entity. */
> > +#define TU_LOCAL_ENTITY_NAME(NODE) \
> > + (((struct tree_tu_local_entity *)TU_LOCAL_ENTITY_CHECK (NODE))->name)
> > +
> > +/* The source location of the translation-unit-local entity. */
> > +#define TU_LOCAL_ENTITY_LOCATION(NODE) \
> > + (((struct tree_tu_local_entity *)TU_LOCAL_ENTITY_CHECK (NODE))->loc)
> > +
> >
> > /* The list of local parameters introduced by this requires-expression,
> > in the form of a chain of PARM_DECLs. */
> > @@ -1811,7 +1827,8 @@ enum cp_tree_node_structure_enum {
> > TS_CP_LAMBDA_EXPR,
> > TS_CP_TEMPLATE_INFO,
> > TS_CP_CONSTRAINT_INFO,
> > - TS_CP_USERDEF_LITERAL
> > + TS_CP_USERDEF_LITERAL,
> > + TS_CP_TU_LOCAL_ENTITY
> > };
> >
> > /* The resulting tree type. */
> > @@ -1842,6 +1859,8 @@ union GTY((desc ("cp_tree_node_structure (&%h)"),
> > constraint_info;
> > struct tree_userdef_literal GTY ((tag ("TS_CP_USERDEF_LITERAL")))
> > userdef_literal;
> > + struct tree_tu_local_entity GTY ((tag ("TS_CP_TU_LOCAL_ENTITY")))
> > + tu_local_entity;
> > };
> >
> >
> > diff --git a/gcc/cp/module.cc b/gcc/cp/module.cc
> > index 136ffb1a7ac..4b26dc5d367 100644
> > --- a/gcc/cp/module.cc
> > +++ b/gcc/cp/module.cc
> > @@ -2330,7 +2330,9 @@ private:
> > DB_KIND_BITS = EK_BITS,
> > DB_DEFN_BIT = DB_KIND_BIT + DB_KIND_BITS,
> > DB_IS_MEMBER_BIT, /* Is an out-of-class member. */
> > - DB_TU_LOCAL_BIT, /* It is a TU-local entity. */
> > + DB_TU_LOCAL_BIT, /* Is a TU-local entity. */
> > + DB_REFS_TU_LOCAL_BIT, /* Refers to a TU-local entity (but is not
> > + necessarily an exposure.) */
> > DB_EXPOSURE_BIT, /* Exposes a TU-local entity. */
> > DB_IMPORTED_BIT, /* An imported entity. */
> > DB_UNREACHED_BIT, /* A yet-to-be reached entity. */
> > @@ -2401,7 +2403,9 @@ public:
> > public:
> > bool has_defn () const
> > {
> > - return get_flag_bit<DB_DEFN_BIT> ();
> > + /* Never consider TU-local entities as having definitions, since
> > + we will never be accessing them from importers anyway. */
> > + return get_flag_bit<DB_DEFN_BIT> () && !is_tu_local ();
> > }
> >
> > public:
> > @@ -2416,6 +2420,10 @@ public:
> > {
> > return get_flag_bit<DB_TU_LOCAL_BIT> ();
> > }
> > + bool refs_tu_local () const
> > + {
> > + return get_flag_bit<DB_REFS_TU_LOCAL_BIT> ();
> > + }
> > bool is_exposure () const
> > {
> > return get_flag_bit<DB_EXPOSURE_BIT> ();
> > @@ -2543,11 +2551,13 @@ public:
> > depset *current; /* Current depset being depended. */
> > unsigned section; /* When writing out, the section. */
> > bool reached_unreached; /* We reached an unreached entity. */
> > + bool ignore_tu_local; /* In a context where referencing a TU-local
> > + entity is not an exposure. */
> >
> > public:
> > hash (size_t size, hash *c = NULL)
> > : parent (size), chain (c), current (NULL), section (0),
> > - reached_unreached (false)
> > + reached_unreached (false), ignore_tu_local (false)
> > {
> > worklist.create (size);
> > }
> > @@ -2748,6 +2758,7 @@ static GTY((cache)) decl_tree_cache_map
> > *imported_temploid_friends;
> > /* Tree tags. */
> > enum tree_tag {
> > tt_null, /* NULL_TREE. */
> > + tt_tu_local, /* A TU-local entity. */
> > tt_fixed, /* Fixed vector index. */
> >
> > tt_node, /* By-value node. */
> > @@ -3032,6 +3043,8 @@ private:
> > depset::hash *dep_hash; /* Dependency table. */
> > int ref_num; /* Back reference number. */
> > unsigned section;
> > + bool writing_local_entities; /* Whether we might walk into a TU-local
> > + entity we need to emit placeholders for. */
> > #if CHECKING_P
> > int importedness; /* Checker that imports not occurring
> > inappropriately. +ve imports ok,
> > @@ -3061,6 +3074,18 @@ public:
> > };
> >
> > public:
> > + /* The walk is used for three similar purposes:
> > +
> > + 1. The initial scan for dependencies.
> > + 2. Once dependencies have been found, ordering them.
> > + 3. Writing dependencies to file (streaming_p).
> > +
> > + For cases where it matters, these accessers can be used to determine
> > + which state we're in. */
> > + bool is_initial_scan () const
> > + {
> > + return !streaming_p () && !is_key_order ();
> > + }
> > bool is_key_order () const
> > {
> > return dep_hash->is_key_order ();
> > @@ -3101,6 +3126,10 @@ private:
> > void tree_pair_vec (vec<tree_pair_s, va_gc> *);
> > void tree_list (tree, bool has_purpose);
> >
> > +private:
> > + bool has_tu_local_dep (tree) const;
> > + tree find_tu_local_decl (tree);
> > +
> > public:
> > /* Mark a node for by-value walking. */
> > void mark_by_value (tree);
> > @@ -3138,7 +3167,7 @@ public:
> >
> > public:
> > /* Serialize various definitions. */
> > - void write_definition (tree decl);
> > + void write_definition (tree decl, bool refs_tu_local = false);
> > void mark_declaration (tree decl, bool do_defn);
> >
> > private:
> > @@ -3166,6 +3195,7 @@ private:
> > static unsigned tree_val_count;
> > static unsigned decl_val_count;
> > static unsigned back_ref_count;
> > + static unsigned tu_local_count;
> > static unsigned null_count;
> > };
> > } // anon namespace
> > @@ -3174,12 +3204,14 @@ private:
> > unsigned trees_out::tree_val_count;
> > unsigned trees_out::decl_val_count;
> > unsigned trees_out::back_ref_count;
> > +unsigned trees_out::tu_local_count;
> > unsigned trees_out::null_count;
> >
> > trees_out::trees_out (allocator *mem, module_state *state, depset::hash
> > &deps,
> > unsigned section)
> > :parent (mem), state (state), tree_map (500),
> > - dep_hash (&deps), ref_num (0), section (section)
> > + dep_hash (&deps), ref_num (0), section (section),
> > + writing_local_entities (false)
> > {
> > #if CHECKING_P
> > importedness = 0;
> > @@ -4301,6 +4333,9 @@ dumper::impl::nested_name (tree t)
> > int origin = -1;
> > tree name = NULL_TREE;
> >
> > + if (t && TREE_CODE (t) == TU_LOCAL_ENTITY)
> > + t = TU_LOCAL_ENTITY_NAME (t);
> > +
> > if (t && TREE_CODE (t) == TREE_BINFO)
> > t = BINFO_TYPE (t);
> >
> > @@ -4853,6 +4888,7 @@ trees_out::instrument ()
> > dump (" %u decl trees", decl_val_count);
> > dump (" %u other trees", tree_val_count);
> > dump (" %u back references", back_ref_count);
> > + dump (" %u TU-local entities", tu_local_count);
> > dump (" %u null trees", null_count);
> > }
> > }
> > @@ -7809,6 +7845,17 @@ trees_out::decl_value (tree decl, depset *dep)
> > || DECL_ORIGINAL_TYPE (decl)
> > || !TYPE_PTRMEMFUNC_P (TREE_TYPE (decl)));
> >
> > + /* There's no need to walk any of the contents of a known TU-local
> > entity,
> > + since importers should never see any of it regardless. But make sure
> > we
> > + at least note its location so importers can use it for diagnostics.
> > */
> > + if (dep && dep->is_tu_local ())
> > + {
> > + gcc_checking_assert (is_initial_scan ());
> > + insert (decl, WK_value);
> > + state->note_location (DECL_SOURCE_LOCATION (decl));
> > + return;
> > + }
> > +
> > merge_kind mk = get_merge_kind (decl, dep);
> > bool is_imported_temploid_friend = imported_temploid_friends->get (decl);
> >
> > @@ -8390,14 +8437,17 @@ trees_in::decl_value ()
> > /* Frob it to be ready for cloning. */
> > TREE_TYPE (inner) = DECL_ORIGINAL_TYPE (inner);
> > DECL_ORIGINAL_TYPE (inner) = NULL_TREE;
> > - set_underlying_type (inner);
> > - if (tdef_flags & 2)
> > + if (TREE_CODE (TREE_TYPE (inner)) != TU_LOCAL_ENTITY)
> > {
> > - /* Match instantiate_alias_template's handling. */
> > - tree type = TREE_TYPE (inner);
> > - TYPE_DEPENDENT_P (type) = true;
> > - TYPE_DEPENDENT_P_VALID (type) = true;
> > - SET_TYPE_STRUCTURAL_EQUALITY (type);
> > + set_underlying_type (inner);
> > + if (tdef_flags & 2)
> > + {
> > + /* Match instantiate_alias_template's handling. */
> > + tree type = TREE_TYPE (inner);
> > + TYPE_DEPENDENT_P (type) = true;
> > + TYPE_DEPENDENT_P_VALID (type) = true;
> > + SET_TYPE_STRUCTURAL_EQUALITY (type);
> > + }
> > }
> > }
> >
> > @@ -8902,10 +8952,14 @@ trees_out::decl_node (tree decl, walk_kind ref)
> > }
> > tree_node (tpl);
> >
> > - /* Streaming TPL caused us to visit DECL and maybe its type. */
> > - gcc_checking_assert (TREE_VISITED (decl));
> > - if (DECL_IMPLICIT_TYPEDEF_P (decl))
> > - gcc_checking_assert (TREE_VISITED (TREE_TYPE (decl)));
> > + /* Streaming TPL caused us to visit DECL and maybe its type,
> > + if it wasn't TU-local. */
> > + if (CHECKING_P && !has_tu_local_dep (tpl))
> > + {
> > + gcc_checking_assert (TREE_VISITED (decl));
> > + if (DECL_IMPLICIT_TYPEDEF_P (decl))
> > + gcc_checking_assert (TREE_VISITED (TREE_TYPE (decl)));
> > + }
> > return false;
> > }
> >
> > @@ -8925,10 +8979,10 @@ trees_out::decl_node (tree decl, walk_kind ref)
> > dep = dep_hash->add_dependency (decl, kind);
> > }
> >
> > - if (!dep)
> > + if (!dep || dep->is_tu_local ())
> > {
> > /* Some internal entity of context. Do by value. */
> > - decl_value (decl, NULL);
> > + decl_value (decl, dep);
> > return false;
> > }
> >
> > @@ -9084,7 +9138,10 @@ trees_out::type_node (tree type)
> > if (streaming_p ())
> > dump (dumper::TREE) && dump ("Wrote typedef %C:%N%S",
> > TREE_CODE (name), name, name);
> > - gcc_checking_assert (TREE_VISITED (type));
> > +
> > + /* We'll have either visited this type or have newly discovered
> > + that it's TU-local; either way we won't need to visit it again. */
> > + gcc_checking_assert (TREE_VISITED (type) || has_tu_local_dep (name));
> > return;
> > }
> >
> > @@ -9363,6 +9420,64 @@ trees_in::tree_value ()
> > return existing;
> > }
> >
> > +/* Whether DECL has a TU-local dependency in the hash. */
> > +
> > +bool
> > +trees_out::has_tu_local_dep (tree decl) const
> > +{
> > + /* Only the contexts of fields or enums remember that they're
> > + TU-local. */
> > + if (DECL_CONTEXT (decl)
> > + && (TREE_CODE (decl) == FIELD_DECL
> > + || TREE_CODE (decl) == CONST_DECL))
> > + decl = TYPE_NAME (DECL_CONTEXT (decl));
> > +
> > + depset *dep = dep_hash->find_dependency (decl);
> > + return dep && dep->is_tu_local ();
> > +}
> > +
> > +/* If T depends on a TU-local entity, return that decl. */
> > +
> > +tree
> > +trees_out::find_tu_local_decl (tree t)
> > +{
> > + /* We need to have walked all deps first before we can check. */
> > + gcc_checking_assert (!is_initial_scan ());
> > +
> > + auto walker = [](tree *tp, int *walk_subtrees, void *data) -> tree
> > + {
> > + auto self = (trees_out *)data;
> > +
> > + tree decl = NULL_TREE;
> > + if (TYPE_P (*tp))
> > + {
> > + /* A PMF type is a record type, which we otherwise wouldn't walk;
> > + return whether the function type is TU-local. */
> > + if (TYPE_PTRMEMFUNC_P (*tp))
> > + {
> > + *walk_subtrees = 0;
> > + return self->find_tu_local_decl (TYPE_PTRMEMFUNC_FN_TYPE (*tp));
> > + }
> > + else
> > + decl = TYPE_MAIN_DECL (*tp);
> > + }
> > + else if (DECL_P (*tp))
> > + decl = *tp;
> > +
> > + if (decl)
> > + {
> > + /* We found a DECL, this will tell us whether we're TU-local. */
> > + *walk_subtrees = 0;
> > + return self->has_tu_local_dep (decl) ? decl : NULL_TREE;
> > + }
> > + return NULL_TREE;
> > + };
> > +
> > + /* We need to walk without duplicates so that we step into the pointed-to
> > + types of array types. */
> > + return cp_walk_tree_without_duplicates (&t, walker, this);
> > +}
> > +
> > /* Stream out tree node T. We automatically create local back
> > references, which is essentially a single pass lisp
> > self-referential structure pretty-printer. */
> > @@ -9375,6 +9490,46 @@ trees_out::tree_node (tree t)
> > if (ref == WK_none)
> > goto done;
> >
> > + /* Find TU-local entities and intercept streaming to instead write a
> > + placeholder value; this way we don't need to emit such decls.
> > + We only need to do this when writing a definition of an entity
> > + that we know names a TU-local entity. */
> > + if (!is_initial_scan () && writing_local_entities)
> > + {
> > + tree local_decl = NULL_TREE;
> > + if (DECL_P (t) && has_tu_local_dep (t))
> > + local_decl = t;
> > + /* Consider a type to be TU-local if it refers to any TU-local decl,
> > + no matter how deep.
> > +
> > + This worsens diagnostics slightly, as we often no longer point
> > + directly to the at-fault entity when instantiating. However, this
> > + reduces the module size slightly and means that much less of pt.cc
> > + needs to know about us. */
> > + else if (TYPE_P (t))
> > + local_decl = find_tu_local_decl (t);
> > + else if (EXPR_P (t))
> > + local_decl = find_tu_local_decl (TREE_TYPE (t));
> > +
> > + if (local_decl)
> > + {
> > + int tag = insert (t, WK_value);
> > + if (streaming_p ())
> > + {
> > + tu_local_count++;
> > + i (tt_tu_local);
> > + dump (dumper::TREE)
> > + && dump ("Writing TU-local entity:%d %C:%N",
> > + tag, TREE_CODE (t), t);
> > + }
> > + /* TODO: Get a more descriptive name? */
> > + tree_node (DECL_NAME (local_decl));
> > + if (state)
> > + state->write_location (*this, DECL_SOURCE_LOCATION (local_decl));
> > + goto done;
> > + }
> > + }
> > +
> > if (ref != WK_normal)
> > goto skip_normal;
> >
> > @@ -9531,6 +9686,18 @@ trees_in::tree_node (bool is_use)
> > /* NULL_TREE. */
> > break;
> >
> > + case tt_tu_local:
> > + {
> > + /* A translation-unit-local entity. */
> > + res = make_node (TU_LOCAL_ENTITY);
> > + int tag = insert (res);
> > +
> > + TU_LOCAL_ENTITY_NAME (res) = tree_node ();
> > + TU_LOCAL_ENTITY_LOCATION (res) = state->read_location (*this);
> > + dump (dumper::TREE) && dump ("Read TU-local entity:%d %N", tag, res);
> > + }
> > + break;
> > +
> > case tt_fixed:
> > /* A fixed ref, find it in the fixed_ref array. */
> > {
> > @@ -10147,7 +10314,8 @@ trees_in::tree_node (bool is_use)
> > /* A template. */
> > if (tree tpl = tree_node ())
> > {
> > - res = DECL_TEMPLATE_RESULT (tpl);
> > + res = (TREE_CODE (tpl) == TU_LOCAL_ENTITY ?
> > + tpl : DECL_TEMPLATE_RESULT (tpl));
> > dump (dumper::TREE)
> > && dump ("Read template %C:%N", TREE_CODE (res), res);
> > }
> > @@ -11917,8 +12085,18 @@ void
> > trees_out::write_function_def (tree decl)
> > {
> > tree_node (DECL_RESULT (decl));
> > - tree_node (DECL_INITIAL (decl));
> > - tree_node (DECL_SAVED_TREE (decl));
> > +
> > + {
> > + /* The function body for a non-inline function or function template
> > + is ignored for determining exposures. This should only matter
> > + for templates (we don't emit the bodies of non-inline functions
> > + to begin with). */
> > + auto ovr = make_temp_override (dep_hash->ignore_tu_local,
> > + !DECL_DECLARED_INLINE_P (decl));
> > + tree_node (DECL_INITIAL (decl));
> > + tree_node (DECL_SAVED_TREE (decl));
> > + }
> > +
> > tree_node (DECL_FRIEND_CONTEXT (decl));
> >
> > constexpr_fundef *cexpr = retrieve_constexpr_fundef (decl);
> > @@ -12020,6 +12198,10 @@ trees_in::read_function_def (tree decl, tree
> > maybe_template)
> > void
> > trees_out::write_var_def (tree decl)
> > {
> > + /* The initializer of a variable or variable template is ignored for
> > + determining exposures. */
> > + auto ovr = make_temp_override (dep_hash->ignore_tu_local, VAR_P (decl));
> > +
> > tree init = DECL_INITIAL (decl);
> > tree_node (init);
> > if (!init)
> > @@ -12207,21 +12389,28 @@ trees_out::write_class_def (tree defn)
> > for (; vtables; vtables = TREE_CHAIN (vtables))
> > write_definition (vtables);
> >
> > - /* Write the friend classes. */
> > - tree_list (CLASSTYPE_FRIEND_CLASSES (type), false);
> > + {
> > + /* Friend declarations in class definitions are ignored when
> > + determining exposures. */
> > + auto ovr = make_temp_override (dep_hash->ignore_tu_local, true);
> >
> > - /* Write the friend functions. */
> > - for (tree friends = DECL_FRIENDLIST (defn);
> > - friends; friends = TREE_CHAIN (friends))
> > - {
> > - /* Name of these friends. */
> > - tree_node (TREE_PURPOSE (friends));
> > - tree_list (TREE_VALUE (friends), false);
> > - }
> > - /* End of friend fns. */
> > - tree_node (NULL_TREE);
> > + /* Write the friend classes. */
> > + tree_list (CLASSTYPE_FRIEND_CLASSES (type), false);
> >
> > - /* Write the decl list. */
> > + /* Write the friend functions. */
> > + for (tree friends = DECL_FRIENDLIST (defn);
> > + friends; friends = TREE_CHAIN (friends))
> > + {
> > + tree_node (FRIEND_NAME (friends));
> > + tree_list (FRIEND_DECLS (friends), false);
> > + }
> > + /* End of friend fns. */
> > + tree_node (NULL_TREE);
> > + }
> > +
> > + /* Write the decl list. We don't need to ignore exposures of friend
> > + decls here as any such decls should already have been added and
> > + ignored above. */
> > tree_list (CLASSTYPE_DECL_LIST (type), true);
> >
> > if (TYPE_CONTAINS_VPTR_P (type))
> > @@ -12574,6 +12763,8 @@ trees_in::read_class_def (tree defn, tree
> > maybe_template)
> > friend_decls; friend_decls = TREE_CHAIN (friend_decls))
> > {
> > tree f = TREE_VALUE (friend_decls);
> > + if (TREE_CODE (f) == TU_LOCAL_ENTITY)
> > + continue;
> >
> > DECL_BEFRIENDING_CLASSES (f)
> > = tree_cons (NULL_TREE, type, DECL_BEFRIENDING_CLASSES (f));
> > @@ -12722,8 +12913,11 @@ trees_in::read_enum_def (tree defn, tree
> > maybe_template)
> > /* Write out the body of DECL. See above circularity note. */
> >
> > void
> > -trees_out::write_definition (tree decl)
> > +trees_out::write_definition (tree decl, bool refs_tu_local)
> > {
> > + auto ovr = make_temp_override (writing_local_entities,
> > + writing_local_entities || refs_tu_local);
> > +
> > if (streaming_p ())
> > {
> > assert_definition (decl);
> > @@ -13309,7 +13503,11 @@ depset::hash::add_dependency (depset *dep)
> > current->deps.safe_push (dep);
> >
> > if (dep->is_tu_local ())
> > - current->set_flag_bit<DB_EXPOSURE_BIT> ();
> > + {
> > + current->set_flag_bit<DB_REFS_TU_LOCAL_BIT> ();
> > + if (!ignore_tu_local)
> > + current->set_flag_bit<DB_EXPOSURE_BIT> ();
> > + }
> >
> > if (current->get_entity_kind () == EK_USING
> > && DECL_IMPLICIT_TYPEDEF_P (dep->get_entity ())
> > @@ -13959,7 +14157,7 @@ depset::hash::find_dependencies (module_state
> > *module)
> > {
> > walker.mark_declaration (decl, current->has_defn ());
> >
> > - if (!walker.is_key_order ()
> > + if (!is_key_order ()
> > && (item->get_entity_kind () == EK_SPECIALIZATION
> > || item->get_entity_kind () == EK_PARTIAL
> > || (item->get_entity_kind () == EK_DECL
> > @@ -13971,15 +14169,15 @@ depset::hash::find_dependencies (module_state
> > *module)
> >
> > walker.decl_value (decl, current);
> > if (current->has_defn ())
> > - walker.write_definition (decl);
> > + walker.write_definition (decl, current->refs_tu_local ());
> > }
> > walker.end ();
> >
> > - if (!walker.is_key_order ()
> > + if (!is_key_order ()
> > && DECL_CLASS_TEMPLATE_P (decl))
> > add_deduction_guides (decl);
> >
> > - if (!walker.is_key_order ()
> > + if (!is_key_order ()
> > && TREE_CODE (decl) == TEMPLATE_DECL
> > && !DECL_UNINSTANTIATED_TEMPLATE_FRIEND_P (decl))
> > {
> > @@ -14168,6 +14366,37 @@ depset::hash::finalize_dependencies ()
> > /* We should have emitted an error above. */
> > gcc_checking_assert (explained);
> > }
> > + else if (warn_template_names_tu_local
> > + && dep->refs_tu_local () && !dep->is_tu_local ())
> > + {
> > + tree decl = dep->get_entity ();
> > +
> > + /* Friend decls in a class body are ignored, but this is harmless:
> > + it should not impact any consumers. */
> > + if (RECORD_OR_UNION_TYPE_P (TREE_TYPE (decl)))
> > + continue;
> > +
> > + /* We should now only be warning about templates. */
> > + gcc_checking_assert
> > + (TREE_CODE (decl) == TEMPLATE_DECL
> > + && VAR_OR_FUNCTION_DECL_P (DECL_TEMPLATE_RESULT (decl)));
> > +
> > + /* Ideally we would only warn in cases where there are no explicit
> > + instantiations of the template, but we don't currently track this
> > + in an easy-to-find way. */
> > + for (depset *rdep : dep->deps)
> > + if (!rdep->is_binding () && rdep->is_tu_local ())
> > + {
> > + tree ref = rdep->get_entity ();
> > + auto_diagnostic_group d;
> > + if (warning_at (DECL_SOURCE_LOCATION (decl),
> > + OPT_Wtemplate_names_tu_local,
> > + "%qD refers to TU-local entity %qD and cannot "
> > + "be instantiated in other TUs", decl, ref))
> > + is_tu_local_entity (ref, /*explain=*/true);
> > + break;
> > + }
> > + }
> > }
> >
> > return ok;
> > @@ -15331,8 +15560,9 @@ enum ct_bind_flags
> > void
> > module_state::intercluster_seed (trees_out &sec, unsigned index_hwm,
> > depset *dep)
> > {
> > - if (dep->is_import ()
> > - || dep->cluster < index_hwm)
> > + if (dep->is_tu_local ())
> > + /* We only stream placeholders for TU-local entities anyway. */;
> > + else if (dep->is_import () || dep->cluster < index_hwm)
> > {
> > tree ent = dep->get_entity ();
> > if (!TREE_VISITED (ent))
> > @@ -15553,7 +15783,7 @@ module_state::write_cluster (elf_out *to, depset
> > *scc[], unsigned size,
> > sec.u (ct_defn);
> > sec.tree_node (decl);
> > dump () && dump ("Writing definition %N", decl);
> > - sec.write_definition (decl);
> > + sec.write_definition (decl, b->refs_tu_local ());
> >
> > if (!namer->has_defn ())
> > namer = b;
> > diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
> > index 03a1144765b..c7c6da0969e 100644
> > --- a/gcc/cp/pt.cc
> > +++ b/gcc/cp/pt.cc
> > @@ -9881,6 +9881,71 @@ add_pending_template (tree d)
> > pop_tinst_level ();
> > }
> >
> > +/* Emit a diagnostic about instantiating a reference to TU-local entity E.
> > */
> > +
> > +static void
> > +complain_about_tu_local_entity (tree e)
> > +{
> > + auto_diagnostic_group d;
> > + error ("instantiation exposes TU-local entity %qD",
> > + TU_LOCAL_ENTITY_NAME (e));
> > + inform (TU_LOCAL_ENTITY_LOCATION (e), "declared here");
> > +}
> > +
> > +/* Checks if T contains a TU-local entity. */
> > +
> > +static bool
> > +expr_contains_tu_local_entity (tree t)
> > +{
> > + if (!modules_p ())
> > + return false;
> > +
> > + auto walker = [](tree *tp, int *walk_subtrees, void *) -> tree
> > + {
> > + if (TREE_CODE (*tp) == TU_LOCAL_ENTITY)
> > + return *tp;
> > + if (!EXPR_P (*tp))
> > + *walk_subtrees = false;
> > + return NULL_TREE;
> > + };
> > + return cp_walk_tree (&t, walker, nullptr, nullptr);
> > +}
> > +
> > +/* Errors and returns TRUE if X is a function that contains a TU-local
> > + entity in its overload set. */
> > +
> > +static bool
> > +function_contains_tu_local_entity (tree x)
> > +{
> > + if (!modules_p ())
> > + return false;
> > +
> > + if (!x || x == error_mark_node)
> > + return false;
> > +
> > + if (TREE_CODE (x) == OFFSET_REF
> > + || TREE_CODE (x) == COMPONENT_REF)
> > + x = TREE_OPERAND (x, 1);
> > + x = MAYBE_BASELINK_FUNCTIONS (x);
> > + if (TREE_CODE (x) == TEMPLATE_ID_EXPR)
> > + x = TREE_OPERAND (x, 0);
> > +
> > + if (OVL_P (x))
> > + for (tree ovl : lkp_range (x))
> > + if (TREE_CODE (ovl) == TU_LOCAL_ENTITY)
> > + {
> > + x = ovl;
> > + break;
> > + }
> > +
> > + if (TREE_CODE (x) == TU_LOCAL_ENTITY)
> > + {
> > + complain_about_tu_local_entity (x);
> > + return true;
> > + }
> > +
> > + return false;
> > +}
> >
> > /* Return a TEMPLATE_ID_EXPR corresponding to the indicated FNS and
> > ARGLIST. Valid choices for FNS are given in the cp-tree.def
> > @@ -12743,8 +12808,10 @@ instantiate_class_template (tree type)
> > }
> > else
> > {
> > - if (TYPE_P (t) || DECL_CLASS_TEMPLATE_P (t)
> > - || DECL_TEMPLATE_TEMPLATE_PARM_P (t))
> > + if (TREE_CODE (t) == TU_LOCAL_ENTITY)
> > + /* Ignore. */;
> > + else if (TYPE_P (t) || DECL_CLASS_TEMPLATE_P (t)
> > + || DECL_TEMPLATE_TEMPLATE_PARM_P (t))
> > {
> > /* Build new CLASSTYPE_FRIEND_CLASSES. */
> >
> > @@ -15522,7 +15589,8 @@ tsubst_decl (tree t, tree args, tsubst_flags_t
> > complain,
> > RETURN (error_mark_node);
> >
> > if (TREE_CODE (t) == TYPE_DECL
> > - && t == TYPE_MAIN_DECL (TREE_TYPE (t)))
> > + && (TREE_CODE (TREE_TYPE (t)) == TU_LOCAL_ENTITY
> > + || t == TYPE_MAIN_DECL (TREE_TYPE (t))))
> > {
> > /* If this is the canonical decl, we don't have to
> > mess with instantiations, and often we can't (for
> > @@ -16250,6 +16318,14 @@ tsubst (tree t, tree args, tsubst_flags_t
> > complain, tree in_decl)
> > || TREE_CODE (t) == TRANSLATION_UNIT_DECL)
> > return t;
> >
> > + /* Any instantiation of a template containing a TU-local entity is an
> > + exposure, so always issue a hard error irrespective of complain. */
> > + if (TREE_CODE (t) == TU_LOCAL_ENTITY)
> > + {
> > + complain_about_tu_local_entity (t);
> > + return error_mark_node;
> > + }
> > +
> > tsubst_flags_t tst_ok_flag = (complain & tf_tst_ok);
> > complain &= ~tf_tst_ok;
> >
> > @@ -18486,6 +18562,12 @@ dependent_operand_p (tree t)
> > {
> > while (TREE_CODE (t) == IMPLICIT_CONV_EXPR)
> > t = TREE_OPERAND (t, 0);
> > +
> > + /* If we contain a TU_LOCAL_ENTITY assume we're non-dependent; we'll
> > error
> > + later when instantiating. */
> > + if (expr_contains_tu_local_entity (t))
> > + return false;
>
> I think it'd be more robust and cheaper (avoiding a separate tree walk)
> to teach the general constexpr/dependence predicates about
> TU_LOCAL_ENTITY instead of handling it only here.
>
This was what I'd initially tried, but had ran into some issues with
handling call expressions I believe, and felt that this was a simpler
way to avoid needing too many special cases and touching more things.
That said I agree that this would probably be nicer! I'll try to take
another look at this if I get a chance.
> > +
> > ++processing_template_decl;
> > bool r = (potential_constant_expression (t)
> > ? value_dependent_expression_p (t)
> > @@ -20255,6 +20337,9 @@ tsubst_expr (tree t, tree args, tsubst_flags_t
> > complain, tree in_decl)
> > else
> > object = NULL_TREE;
> >
> > + if (function_contains_tu_local_entity (templ))
> > + RETURN (error_mark_node);
> > +
> > tree tid = lookup_template_function (templ, targs);
> > protected_set_expr_location (tid, EXPR_LOCATION (t));
> >
> > @@ -20947,6 +21032,9 @@ tsubst_expr (tree t, tree args, tsubst_flags_t
> > complain, tree in_decl)
> > qualified_p = true;
> > }
> >
> > + if (function_contains_tu_local_entity (function))
> > + RETURN (error_mark_node);
>
> Similarly, maybe it'd suffice to check this more generally in the
> OVERLOAD case of tsubst_expr?
>
Good thought, I'll give this a shot at some point.
> > +
> > nargs = call_expr_nargs (t);
> > releasing_vec call_args;
> > tsubst_call_args (t, args, complain, in_decl, call_args);
> > @@ -21968,6 +22056,10 @@ tsubst_expr (tree t, tree args, tsubst_flags_t
> > complain, tree in_decl)
> > RETURN (op);
> > }
> >
> > + case TU_LOCAL_ENTITY:
> > + complain_about_tu_local_entity (t);
> > + RETURN (error_mark_node);
> > +
> > default:
> > /* Handle Objective-C++ constructs, if appropriate. */
> > if (tree subst = objcp_tsubst_expr (t, args, complain, in_decl))
> > diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
> > index d38c1feb86f..b5f767f6f12 100644
> > --- a/gcc/doc/invoke.texi
> > +++ b/gcc/doc/invoke.texi
> > @@ -272,7 +272,7 @@ in the following sections.
> > -Woverloaded-virtual -Wno-pmf-conversions -Wself-move -Wsign-promo
> > -Wsized-deallocation -Wsuggest-final-methods
> > -Wsuggest-final-types -Wsuggest-override -Wno-template-body
> > --Wno-template-id-cdtor
> > +-Wno-template-id-cdtor -Wtemplate-names-tu-local
> > -Wno-terminate -Wno-vexing-parse -Wvirtual-inheritance
> > -Wno-virtual-move-assign -Wvolatile -Wzero-as-null-pointer-constant}
> >
> > @@ -4686,6 +4686,23 @@ template<typename T> struct S @{
> > @option{-Wtemplate-id-cdtor} is enabled by default with
> > @option{-std=c++20}; it is also enabled by @option{-Wc++20-compat}.
> >
> > +@opindex Wtemplate-names-tu-local
> > +@opindex Wno-template-names-tu-local
> > +@item -Wtemplate-names-tu-local
> > +Warn when a template body hides an exposure of a translation-unit-local
> > +entity. In most cases, referring to a translation-unit-local entity
> > +(such as an internal linkage declaration) within an entity that is
> > +emitted into a module's CMI is an error. However, within the
> > +initializer of a variable, or in the body of a non-inline function,
> > +this is not an exposure and no error is emitted.
> > +
> > +This can cause variable or function templates to accidentally become
> > +unusable if they reference such an entity, because other translation
> > +units that import the template will never be able to instantiate it.
> > +This warning attempts to detect cases where this might occur.
> > +
> > +This flag is enabled by @option{-Wextra}.
> > +
> > @opindex Wterminate
> > @opindex Wno-terminate
> > @item -Wno-terminate @r{(C++ and Objective-C++ only)}
> > diff --git a/gcc/testsuite/g++.dg/modules/internal-5_a.C
> > b/gcc/testsuite/g++.dg/modules/internal-5_a.C
> > new file mode 100644
> > index 00000000000..c5ef3752f5a
> > --- /dev/null
> > +++ b/gcc/testsuite/g++.dg/modules/internal-5_a.C
> > @@ -0,0 +1,110 @@
> > +// { dg-additional-options "-fmodules-ts -Wtemplate-names-tu-local" }
> > +// { dg-module-cmi M }
> > +// Ignore exposures in these cases
> > +
> > +export module M;
> > +
> > +namespace {
> > + inline namespace ns {
> > + struct internal_t {};
> > + template <typename T> struct internal_tmpl_t {};
> > +
> > + int internal_x;
> > + void internal_ovl(int&) {}
> > + void internal_ovl(internal_t) {}
> > +
> > + template <typename T> void internal_tmpl() {}
> > + }
> > +}
> > +export struct ok_inst_tag {};
> > +
> > +
> > +// The function body for a non-inline function or function template
> > +export void function() {
> > + internal_t i {};
> > + internal_tmpl_t<int> ii {};
> > + internal_ovl(internal_x);
> > + internal_tmpl<int>();
> > +}
> > +
> > +export template <typename T> void function_tmpl() { // { dg-warning
> > "refers to TU-local entity" }
> > + internal_t i {};
> > + internal_tmpl_t<T> ii {};
> > + internal_ovl(internal_x);
> > + internal_tmpl<T>();
> > +}
> > +template void function_tmpl<ok_inst_tag>();
> > +template <> void function_tmpl<ok_inst_tag*>() {}
> > +
> > +
> > +// The initializer for a variable or variable template
> > +export int var
> > + = (internal_t{}, internal_tmpl_t<int>{},
> > + internal_ovl(internal_x), internal_tmpl<int>(), 0);
> > +
> > +export template <typename T> int var_tmpl // { dg-warning "refers to
> > TU-local entity" }
> > + = (internal_t{}, internal_tmpl_t<T>{},
> > + internal_ovl(internal_x), internal_tmpl<T>(), 0);
> > +
> > +template <typename T> int var_tmpl<T*> // { dg-warning "refers to
> > TU-local entity" }
> > + = (internal_t{}, internal_tmpl_t<T*>{},
> > + internal_ovl(internal_x), internal_tmpl<T*>(), 0);
> > +
> > +template int var_tmpl<ok_inst_tag>;
> > +template <> int var_tmpl<ok_inst_tag*> = 0;
> > +
> > +export int& constant_ref = internal_x;
> > +static_assert (&constant_ref == &internal_x);
> > +
> > +
> > +// Friend declarations in a class definition
> > +export struct klass { // { dg-bogus "TU-local" }
> > + friend ns::internal_t;
> > + friend ns::internal_tmpl_t<int>;
> > + friend void ns::internal_ovl(int&);
> > + friend void ns::internal_ovl(internal_t);
> > + friend void ns::internal_tmpl<int>();
> > +
> > + template <typename> friend struct ns::internal_tmpl_t;
> > + template <typename> friend void ns::internal_tmpl();
> > +};
> > +
> > +export template <typename T>
> > +class klass_tmpl { // { dg-bogus "TU-local" }
> > + friend ns::internal_t;
> > + friend ns::internal_tmpl_t<int>;
> > + friend void ns::internal_ovl(int&);
> > + friend void ns::internal_ovl(internal_t);
> > + friend void ns::internal_tmpl<int>();
> > +
> > + template <typename> friend struct ns::internal_tmpl_t;
> > + template <typename> friend void ns::internal_tmpl();
> > +};
> > +
> > +template <typename T> class klass_tmpl<T*> { // { dg-bogus "TU-local" }
> > + friend ns::internal_t;
> > + friend ns::internal_tmpl_t<int>;
> > + friend void ns::internal_ovl(int&);
> > + friend void ns::internal_ovl(internal_t);
> > + friend void ns::internal_tmpl<int>();
> > +
> > + template <typename> friend struct ns::internal_tmpl_t;
> > + template <typename> friend void ns::internal_tmpl();
> > +};
> > +
> > +
> > +// Any reference to a non-volatile const object or reference with internal
> > or
> > +// no linkage initialized with a constant expression that is not an ODR-use
> > +static const int value = 123;
> > +static const int& ref = 456;
> > +static const internal_t internal {};
> > +void f(int) {}
> > +export inline void no_odr_use() {
> > + int x = value;
> > + int y = ref;
> > + int z = (internal, 0);
> > +
> > + value;
> > + bool b = value < value;
> > + f(value);
> > +}
> > diff --git a/gcc/testsuite/g++.dg/modules/internal-5_b.C
> > b/gcc/testsuite/g++.dg/modules/internal-5_b.C
> > new file mode 100644
> > index 00000000000..baf60fdafa2
> > --- /dev/null
> > +++ b/gcc/testsuite/g++.dg/modules/internal-5_b.C
> > @@ -0,0 +1,30 @@
> > +// { dg-additional-options "-fmodules-ts" }
> > +
> > +import M;
> > +
> > +int main() {
> > + // These are all OK
> > + function();
> > + int a = var;
> > + klass k;
> > + klass_tmpl<int> kt;
> > + klass_tmpl<int*> ktp;
> > + no_odr_use();
> > +
> > + function_tmpl<ok_inst_tag>();
> > + function_tmpl<ok_inst_tag*>();
> > + int b = var_tmpl<ok_inst_tag>;
> > + int c = var_tmpl<ok_inst_tag*>;
> > +
> > + // But don't ignore exposures in these cases
> > + function_tmpl<int>(); // { dg-message "required from here" }
> > + int x = var_tmpl<int>; // { dg-message "required from here" }
> > + int y = var_tmpl<int*>; // { dg-message "required from here" }
> > +
> > + // And decls initialized to a TU-local value are not constant here
> > + // Unfortunately the error does not currently point to this decl
> > + constexpr int& r = constant_ref;
> > + // { dg-error "is not a constant expression" "" { target *-*-* } 0 }
> > +}
> > +
> > +// { dg-error "instantiation exposes TU-local entity" "" { target *-*-* }
> > 0 }
> > diff --git a/gcc/testsuite/g++.dg/modules/internal-6.C
> > b/gcc/testsuite/g++.dg/modules/internal-6.C
> > new file mode 100644
> > index 00000000000..0f138781ad5
> > --- /dev/null
> > +++ b/gcc/testsuite/g++.dg/modules/internal-6.C
> > @@ -0,0 +1,24 @@
> > +// { dg-additional-options "-fmodules-ts" }
> > +// { dg-module-cmi !M }
> > +// Exposures (or not) of TU-local values
> > +
> > +export module M;
> > +
> > +static void f() {}
> > +auto& fr = f; // OK
> > +constexpr auto& fr2 = fr; // { dg-error "initialized to a TU-local value"
> > }
> > +static constexpr auto fp2 = fr; // OK
> > +
> > +struct S { void (&ref)(); } s{ f }; // OK, value is TU-local
> > +constexpr extern struct W { S& s; } wrap{ s }; // OK, value is not
> > TU-local
> > +constexpr S s2{ f }; // { dg-error "initialized to a TU-local value" }
> > +
> > +constexpr int a = 123;
> > +static constexpr int b = 456;
> > +struct X {
> > + union {
> > + const int* p[2];
> > + };
> > +};
> > +constexpr X x { &a }; // OK
> > +constexpr X y { &a, &b }; // { dg-error "initialized to a TU-local value"
> > }
> > diff --git a/gcc/testsuite/g++.dg/modules/internal-7_a.C
> > b/gcc/testsuite/g++.dg/modules/internal-7_a.C
> > new file mode 100644
> > index 00000000000..39f53ea382e
> > --- /dev/null
> > +++ b/gcc/testsuite/g++.dg/modules/internal-7_a.C
> > @@ -0,0 +1,75 @@
> > +// { dg-additional-options "-fmodules-ts -Wtemplate-names-tu-local" }
> > +// Test streaming and instantiations of various kinds of exposures
> > +
> > +export module M;
> > +
> > +namespace {
> > + int x;
> > + constexpr int y = 1;
> > +
> > + struct S { int m; void d(); };
> > + enum class E { e };
> > +
> > + template <typename T> int f(T t) { return (int)t; }
> > +}
> > +
> > +template <auto N> void g() {}
> > +
> > +template <typename T>
> > +int expose_1() { // { dg-warning "TU-local" }
> > + return x;
> > +}
> > +
> > +template <typename T>
> > +void expose_2() { // { dg-warning "TU-local" }
> > + T t = &y;
> > +}
> > +
> > +template <typename T>
> > +bool expose_3() { // { dg-warning "TU-local" }
> > + return !(T{} * (x + 5) > 123);
> > +}
> > +
> > +template <typename T>
> > +bool expose_4() { // { dg-warning "TU-local" }
> > + return __is_same(S, T);
> > +}
> > +
> > +template <typename T>
> > +void expose_5() { // { dg-warning "TU-local" }
> > + static_assert(T{} == (int)E::e);
> > +}
> > +
> > +template <typename T>
> > +void expose_6() { // { dg-warning "TU-local" }
> > + f(T{});
> > +}
> > +
> > +template <typename T>
> > +void expose_7() { // { dg-warning "TU-local" }
> > + g<&y>();
> > +}
> > +
> > +template <typename T>
> > +void expose_8() { // { dg-warning "TU-local" }
> > + decltype(T{} .* &S::m)* (*x)[5][10];
> > +};
> > +
> > +template <typename T>
> > +bool expose_9() { // { dg-warning "TU-local" }
> > + return noexcept((T{} .* &S::d)());
> > +}
> > +
> > +template <typename T>
> > +void expose_10() { // { dg-warning "TU-local" }
> > + using U = decltype(f<T>());
> > +}
> > +
> > +template <typename T>
> > +void expose_11() { // { dg-warning "TU-local" }
> > + static thread_local E r;
> > +}
> > +
> > +template <typename T>
> > +int expose_var // { dg-warning "TU-local" }
> > + = f(sizeof(T));
> > diff --git a/gcc/testsuite/g++.dg/modules/internal-7_b.C
> > b/gcc/testsuite/g++.dg/modules/internal-7_b.C
> > new file mode 100644
> > index 00000000000..2a11e449d6e
> > --- /dev/null
> > +++ b/gcc/testsuite/g++.dg/modules/internal-7_b.C
> > @@ -0,0 +1,21 @@
> > +// { dg-additional-options "-fmodules-ts" }
> > +
> > +module M;
> > +
> > +void inst() {
> > + expose_1<int>(); // { dg-message "required from here" }
> > + expose_2<int>(); // { dg-message "required from here" }
> > + expose_3<int>(); // { dg-message "required from here" }
> > + expose_4<int>(); // { dg-message "required from here" }
> > + expose_5<int>(); // { dg-message "required from here" }
> > + expose_6<int>(); // { dg-message "required from here" }
> > + expose_7<int>(); // { dg-message "required from here" }
> > + expose_8<int>(); // { dg-message "required from here" }
> > + expose_9<int>(); // { dg-message "required from here" }
> > + expose_10<int>(); // { dg-message "required from here" }
> > + expose_11<int>(); // { dg-message "required from here" }
> > +
> > + expose_var<int>; // { dg-message "required from here" }
> > +}
> > +
> > +// { dg-error "instantiation exposes TU-local entity" "" { target *-*-* }
> > 0 }
> > diff --git a/gcc/testsuite/g++.dg/modules/internal-8_a.C
> > b/gcc/testsuite/g++.dg/modules/internal-8_a.C
> > new file mode 100644
> > index 00000000000..46e07a23cf0
> > --- /dev/null
> > +++ b/gcc/testsuite/g++.dg/modules/internal-8_a.C
> > @@ -0,0 +1,35 @@
> > +// { dg-additional-options "-fmodules-ts -Wtemplate-names-tu-local" }
> > +// Non-ODR usages of const variables currently are erroneously
> > +// reported in templates and constexpr functions; this test
> > +// XFAILS them until we can implement a fix.
> > +
> > +export module M;
> > +
> > +namespace { struct internal_t {}; };
> > +static const int value = 123;
> > +static const int& ref = 456;
> > +static const internal_t internal {};
> > +
> > +constexpr void f(int) {}
> > +
> > +export constexpr
> > +void no_odr_use_cexpr() { // { dg-bogus "TU-local" "" { xfail *-*-* } }
> > + int x = value;
> > + int y = ref;
> > + int z = (internal, 0);
> > +
> > + value;
> > + bool b = value < value;
> > + f(value);
> > +}
> > +
> > +export template <typename T>
> > +void no_odr_use_templ() { // { dg-bogus "TU-local" "" { xfail *-*-* } }
> > + int x = value;
> > + int y = ref;
> > + int z = (internal, 0);
> > +
> > + value;
> > + bool b = value < value;
> > + f(value);
> > +}
> > diff --git a/gcc/testsuite/g++.dg/modules/xtreme-header-8.C
> > b/gcc/testsuite/g++.dg/modules/xtreme-header-8.C
> > new file mode 100644
> > index 00000000000..82c0b59fefe
> > --- /dev/null
> > +++ b/gcc/testsuite/g++.dg/modules/xtreme-header-8.C
> > @@ -0,0 +1,8 @@
> > +// PR c++/115126
> > +// { dg-additional-options "-fmodules-ts -Wtemplate-names-tu-local" }
> > +// { dg-module-cmi xstd }
> > +
> > +export module xstd;
> > +extern "C++" {
> > + #include "xtreme-header.h"
> > +}
> > --
> > 2.46.0
> >
> >
>
