Tested on x86_64-pc-linux-gnu, does this look OK for trunk?
-- >8 --
Here when streaming in the fields of the as-base version of
_Formatting_scanner<int> we end up clobbering ANON_AGGR_TYPE_FIELD
of the anonymous union type, since it turns out this type is shared
between the original FIELD_DECL and the as-base FIELD_DECL copy (copied
during layout_class_type). ANON_AGGR_TYPE_FIELD first gets properly set
to the original FIELD_DECL when streaming in the canonical definition of
_Formatting_scanner<int>, and then gets overwritten to the as-base
FIELD_DECL when streaming in the the as-base definition. This leads to
lookup_anon_field giving the wrong answer when resolving the _M_values
use.
This patch makes us avoid overwriting ANON_AGGR_TYPE_FIELD when streaming
in an as-base class definition, it should already be properly set at that
point.
PR c++/112580
gcc/cp/ChangeLog:
* module.cc (trees_in::read_class_def): When streaming in
an anonymous union field of an as-base class, don't clobber
ANON_AGGR_TYPE_FIELD.
gcc/testsuite/ChangeLog:
* g++.dg/modules/anon-3_a.H: New test.
* g++.dg/modules/anon-3_b.C: New test.
---
gcc/cp/module.cc | 12 ++++++++++--
gcc/testsuite/g++.dg/modules/anon-3_a.H | 21 +++++++++++++++++++++
gcc/testsuite/g++.dg/modules/anon-3_b.C | 8 ++++++++
3 files changed, 39 insertions(+), 2 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/modules/anon-3_a.H
create mode 100644 gcc/testsuite/g++.dg/modules/anon-3_b.C
diff --git a/gcc/cp/module.cc b/gcc/cp/module.cc
index 3c2fef0e3f4..d36ba2eeeb3 100644
--- a/gcc/cp/module.cc
+++ b/gcc/cp/module.cc
@@ -12178,8 +12178,16 @@ trees_in::read_class_def (tree defn, tree
maybe_template)
if (TREE_CODE (decl) == FIELD_DECL
&& ANON_AGGR_TYPE_P (TREE_TYPE (decl)))
- ANON_AGGR_TYPE_FIELD
- (TYPE_MAIN_VARIANT (TREE_TYPE (decl))) = decl;
+ {
+ tree anon_type = TYPE_MAIN_VARIANT (TREE_TYPE (decl));
+ if (DECL_NAME (defn) == as_base_identifier)
+ /* ANON_AGGR_TYPE_FIELD should already point to the
+ original FIELD_DECL, don't overwrite it to point
+ to the as-base FIELD_DECL copy. */
+ gcc_checking_assert (ANON_AGGR_TYPE_FIELD (anon_type));
+ else
+ ANON_AGGR_TYPE_FIELD (anon_type) = decl;
+ }
if (TREE_CODE (decl) == USING_DECL
&& TREE_CODE (USING_DECL_SCOPE (decl)) == RECORD_TYPE)
diff --git a/gcc/testsuite/g++.dg/modules/anon-3_a.H
b/gcc/testsuite/g++.dg/modules/anon-3_a.H
new file mode 100644
index 00000000000..64a6aab51dd
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/anon-3_a.H
@@ -0,0 +1,21 @@
+// PR c++/112580
+// { dg-additional-options "-fmodule-header" }
+// { dg-module-cmi {} }
+
+template <typename _Out>
+struct _Formatting_scanner {
+ union {
+ int _M_values = 42;
+ };
+ virtual int _M_format_arg() { return _M_values; }
+};
+
+template <typename _Tp>
+auto __do_vformat_to() {
+ _Formatting_scanner<int> s;
+ return s;
+}
+
+inline auto vformat() {
+ return __do_vformat_to<int>();
+}
diff --git a/gcc/testsuite/g++.dg/modules/anon-3_b.C
b/gcc/testsuite/g++.dg/modules/anon-3_b.C
new file mode 100644
index 00000000000..d676fe47536
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/anon-3_b.C
@@ -0,0 +1,8 @@
+// PR c++/112580
+// { dg-additional-options "-fmodules-ts" }
+
+import "anon-3_a.H";
+
+int main() {
+ vformat()._M_format_arg();
+}
--
2.43.0.493.gbc7ee2e5e1
