On 12/18/23 17:10, Jason Merrill wrote:
On 12/18/23 16:57, Nathan Sidwell wrote:
On 12/18/23 16:31, Jason Merrill wrote:
Tested x86_64-pc-linux-gnu. Does this make sense? Did you have another theory
about how to merge these?
Why isn't push_abi_namespace doing the right setup here? (and I think
get_global_binding might be similarly problematic?)
What would the right setup be? It pushes into the global module, but before
this change lookup doesn't find things imported into the global module, and so
we get two independent (and so non-equivalent) declarations.
The comment for get_namespace_binding says "Users of this who, having found
nothing, push a new decl must be prepared for that pushing to match an existing
decl." But if lookup_elaborated_type fails, so we pushtag a new type,
check_module_override doesn't try to merge them because TREE_PUBLIC isn't set on
the TYPE_DECL yet at that point, and they coexist until we complain about
redeclaring __dynamic_cast with non-matching parameter types.
I tried setting TREE_PUBLIC on the TYPE_DECL, and then check_module_override
called duplicate_decls, and rejected the redeclaration as a different type.
sigh, it seems that doesn't work as intended, I guess your approace is a
pragmatic workaround, much as I dislike special-casing particular identifier.
Perhaps comment with an appropriate FIXME?
I've realized there's problems with completeness here -- the 'invisible' type
may be complete, but the current TU only foreward-declares it. Our AST can't
represent that right now. And I'm not sure if there are template instantiation
issues -- is the type complete or not in any particular instantiaton?
nathan
-- 8< --
Doing a dynamic_cast in both TUs broke because we were declaring a new
__class_type_info in _b that conflicted with the one imported in the global
module from _a. lookup_elaborated_type has a comment that we probably don't
want to find such imports in general, but in this case it seems necessary to
make the artificial lazy declarations of RTTI types work.
gcc/cp/ChangeLog:
* name-lookup.cc (lookup_elaborated_type): Look for bindings
in the global namespace in the ABI namespace.
gcc/testsuite/ChangeLog:
* g++.dg/modules/pr106304_b.C: Add dynamic_cast.
---
gcc/cp/name-lookup.cc | 10 ++++++++++
gcc/testsuite/g++.dg/modules/pr106304_b.C | 1 +
2 files changed, 11 insertions(+)
diff --git a/gcc/cp/name-lookup.cc b/gcc/cp/name-lookup.cc
index 09dc6ef3e5a..f15b338025d 100644
--- a/gcc/cp/name-lookup.cc
+++ b/gcc/cp/name-lookup.cc
@@ -8092,6 +8092,16 @@ lookup_elaborated_type (tree name, TAG_how how)
// FIXME: This isn't quite right, if we find something
// here, from the language PoV we're not supposed to
// know it?
+ // We at least need to do this in __cxxabiv1 to unify lazy
+ // declarations of __class_type_info in build_dynamic_cast_1.
+ if (current_namespace == abi_node)
+ {
+ tree g = (BINDING_VECTOR_CLUSTER (*slot, 0)
+ .slots[BINDING_SLOT_GLOBAL]);
+ for (ovl_iterator iter (g); iter; ++iter)
+ if (qualify_lookup (*iter, LOOK_want::TYPE))
+ return *iter;
+ }
}
}
}
diff --git a/gcc/testsuite/g++.dg/modules/pr106304_b.C
b/gcc/testsuite/g++.dg/modules/pr106304_b.C
index e8333909c8d..0d1da086176 100644
--- a/gcc/testsuite/g++.dg/modules/pr106304_b.C
+++ b/gcc/testsuite/g++.dg/modules/pr106304_b.C
@@ -5,4 +5,5 @@ module pr106304;
void f(A& a) {
as_b(a);
+ dynamic_cast<B*>(&a);
}
base-commit: 5347263b347d02e875879ca40ca6e289ac178919
prerequisite-patch-id: 66735c0c7beb22586ed4b632d10ec9094bb9920c
--
Nathan Sidwell
