Bootstrapped and regtested on x86_64-pc-linux-gnu, OK for trunk?
Happy to remove the custom inform for lambdas, but I felt that the
original message (which suggests that defining it within a class should
make it OK) was unhelpful here.
Similarly the 'is_exposure_of_member_type' function is not necessary to
fix the bug, and is just for slightly nicer diagnostics.
-- >8 --
Previously, 'is_tu_local_entity' wouldn't detect the exposure of the (in
practice) TU-local lambda in the following example, unless instantiated:
struct S {
template <typename>
static inline decltype([]{}) x = {};
};
This is for two reasons. Firstly, when traversing the TYPE_FIELDS of S
we only see the TEMPLATE_DECL, and never end up building a dependency on
its DECL_TEMPLATE_RESULT (due to not being instantiated). This patch
fixes this by stripping any templates before checking for unnamed types.
The second reason is that we currently assume all class-scope entities
are not TU-local. Despite this being unambiguous in the standard, this
is not actually true in our implementation just yet, due to issues with
mangling lambdas in some circumstances. Allowing these lambdas to be
exported can cause issues in importers with apparently conflicting
declarations, so this patch treats them as TU-local as well.
After these changes, we now get double diagnostics from the two ways
that we can see the above lambda being exposed, via 'S' (through
TYPE_FIELDS) or via 'S::x'. To workaround this we hide diagnostics from
the first case, so we only get errors from 'S::x' which will be closer
to the point the offending lambda is declared.
gcc/cp/ChangeLog:
* module.cc (trees_out::type_node): Adjust assertion.
(depset::hash::is_tu_local_entity): Handle unnamed template
types, treat lambdas specially.
(is_exposure_of_member_type): New function.
(depset::hash::add_dependency): Use it.
(depset::hash::finalize_dependencies): Likewise.
gcc/testsuite/ChangeLog:
* g++.dg/modules/internal-10.C: New test.
Signed-off-by: Nathaniel Shead <nathanielosh...@gmail.com>
---
gcc/cp/module.cc | 67 ++++++++++++++++++----
gcc/testsuite/g++.dg/modules/internal-10.C | 25 ++++++++
2 files changed, 81 insertions(+), 11 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/modules/internal-10.C
diff --git a/gcc/cp/module.cc b/gcc/cp/module.cc
index c89834c1abd..59b7270f4a5 100644
--- a/gcc/cp/module.cc
+++ b/gcc/cp/module.cc
@@ -9261,7 +9261,9 @@ trees_out::type_node (tree 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));
+ gcc_checking_assert (TREE_VISITED (type)
+ || has_tu_local_dep (TYPE_NAME (type))
+ || has_tu_local_dep (TYPE_TI_TEMPLATE (type)));
return;
}
@@ -13432,19 +13434,31 @@ depset::hash::is_tu_local_entity (tree decl, bool
explain/*=false*/)
We consider types with names for linkage purposes as having names, since
these aren't really TU-local. */
- if (TREE_CODE (decl) == TYPE_DECL
+ tree inner = STRIP_TEMPLATE (decl);
+ if (inner
+ && TREE_CODE (inner) == TYPE_DECL
&& TYPE_ANON_P (type)
- && !DECL_SELF_REFERENCE_P (decl)
+ && !DECL_SELF_REFERENCE_P (inner)
/* An enum with an enumerator name for linkage. */
&& !(UNSCOPED_ENUM_P (type) && TYPE_VALUES (type)))
{
tree main_decl = TYPE_MAIN_DECL (type);
- if (!DECL_CLASS_SCOPE_P (main_decl)
- && !decl_function_context (main_decl)
- /* LAMBDA_EXPR_EXTRA_SCOPE will be set for lambdas defined in
- contexts where they would not be TU-local. */
- && !(LAMBDA_TYPE_P (type)
- && LAMBDA_TYPE_EXTRA_SCOPE (type)))
+ if (LAMBDA_TYPE_P (type))
+ {
+ /* A lambda expression is, in practice, TU-local iff it has no
+ mangling scope. This currently doesn't line up exactly with
+ the standard's definition due to some ABI issues, but it's
+ pretty close, and avoids other issues down the line. */
+ if (!LAMBDA_TYPE_EXTRA_SCOPE (type))
+ {
+ if (explain)
+ inform (loc, "%qT has no name and cannot be differentiated "
+ "from similar lambdas in other TUs", type);
+ return true;
+ }
+ }
+ else if (!DECL_CLASS_SCOPE_P (main_decl)
+ && !decl_function_context (main_decl))
{
if (explain)
inform (loc, "%qT has no name and is not defined within a class, "
@@ -13748,6 +13762,35 @@ depset::hash::make_dependency (tree decl, entity_kind
ek)
return dep;
}
+/* Whether REF is an exposure of a member type of SOURCE.
+
+ This comes up with exposures of class-scope lambdas, that we currently
+ treat as TU-local due to ABI reasons. In such a case the type of the
+ lambda will be exposed in two places, first by the class type it is in
+ the TYPE_FIELDS list of, and second by the actual member declaring that
+ lambda. We only want the second case to warn. */
+
+static bool
+is_exposure_of_member_type (depset *source, depset *ref)
+{
+ gcc_checking_assert (source->refs_tu_local () && ref->is_tu_local ());
+ tree source_entity = STRIP_TEMPLATE (source->get_entity ());
+ tree ref_entity = STRIP_TEMPLATE (ref->get_entity ());
+
+ if (source_entity
+ && ref_entity
+ && DECL_IMPLICIT_TYPEDEF_P (source_entity)
+ && DECL_IMPLICIT_TYPEDEF_P (ref_entity)
+ && DECL_CLASS_SCOPE_P (ref_entity)
+ && DECL_CONTEXT (ref_entity) == TREE_TYPE (source_entity))
+ {
+ gcc_checking_assert (LAMBDA_TYPE_P (TREE_TYPE (ref_entity)));
+ return true;
+ }
+ else
+ return false;
+}
+
/* DEP is a newly discovered dependency. Append it to current's
depset. */
@@ -13760,7 +13803,7 @@ depset::hash::add_dependency (depset *dep)
if (dep->is_tu_local ())
{
current->set_flag_bit<DB_REFS_TU_LOCAL_BIT> ();
- if (!ignore_tu_local)
+ if (!ignore_tu_local && !is_exposure_of_member_type (current, dep))
current->set_flag_bit<DB_EXPOSURE_BIT> ();
}
@@ -14633,7 +14676,9 @@ depset::hash::finalize_dependencies ()
tree decl = dep->get_entity ();
for (depset *rdep : dep->deps)
- if (!rdep->is_binding () && rdep->is_tu_local ())
+ if (!rdep->is_binding ()
+ && rdep->is_tu_local ()
+ && !is_exposure_of_member_type (dep, rdep))
{
// FIXME:QOI Better location information? We're
// losing, so it doesn't matter about efficiency
diff --git a/gcc/testsuite/g++.dg/modules/internal-10.C
b/gcc/testsuite/g++.dg/modules/internal-10.C
new file mode 100644
index 00000000000..e374aaa9145
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/internal-10.C
@@ -0,0 +1,25 @@
+// { dg-additional-options "-fmodules -std=c++20" }
+// { dg-module-cmi !M }
+
+// These are not TU-local according to the standard,
+// but we treat as TU-local due to ABI limitations.
+
+export module M;
+
+struct A {
+ static inline auto x = []{};
+
+ template <typename T>
+ static inline auto y = []{};
+};
+
+struct B {
+ template <typename T>
+ static inline decltype([]{}) x = {}; // { dg-bogus "TU-local" "" { xfail
*-*-* } }
+};
+
+template <typename T>
+struct C {
+ template <typename U>
+ static inline decltype([]{}) x = {}; // { dg-bogus "TU-local" "" { xfail
*-*-* } }
+};
--
2.47.0
