On 1/29/26 4:10 PM, Jakub Jelinek wrote:
On Wed, Jan 28, 2026 at 02:21:43PM +0800, Jason Merrill wrote:
This seems to avoid that while also fixing the testcase; I haven't done any
other testing.
Bootstrapped/regtested successfully on x86_64-linux and i686-linux.
LGTM.
Pushing this:
From 35b17c7713d4bd7a675ee8908724325e957d1482 Mon Sep 17 00:00:00 2001
From: Jason Merrill <[email protected]>
Date: Wed, 28 Jan 2026 14:17:13 +0800
Subject: [PATCH] c++: defer DECL_ONE_ONLY vs consteval-only [PR122785]
To: [email protected]
The failure in the given PR occurs because when setting up an
imported vague-linkage variable, we currently call 'maybe_commonize_var'
which for -freflection checks 'consteval_only_p'. Unfortunately this
latter function needs to call 'complete_type_p' which can perform
recursive loading of the (possibly yet-to-be-streamed) class type,
breaking modules assumptions.
If we just remove the consteval_only_p early exit from maybe_commonize_var,
we end up crashing at EOF while trying to mangle its comdat group, so we
need to undo maybe_commonize_var along with setting DECL_EXTERN.
PR c++/122785
gcc/cp/ChangeLog:
* decl.cc (maybe_commonize_var): Don't check consteval_only_p.
(make_rtl_for_nonlocal_decl): Undo make_decl_one_only for
consteval-only variables.
gcc/testsuite/ChangeLog:
* g++.dg/modules/reflect-1_a.H: New test.
* g++.dg/modules/reflect-1_b.C: New test.
Co-authored-by: Nathaniel Shead <[email protected]>
---
gcc/cp/decl.cc | 11 +++++++----
gcc/testsuite/g++.dg/modules/reflect-1_b.C | 6 ++++++
gcc/testsuite/g++.dg/modules/reflect-1_a.H | 11 +++++++++++
3 files changed, 24 insertions(+), 4 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/modules/reflect-1_b.C
create mode 100644 gcc/testsuite/g++.dg/modules/reflect-1_a.H
diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
index 270158510df..c24bbc889ed 100644
--- a/gcc/cp/decl.cc
+++ b/gcc/cp/decl.cc
@@ -7263,10 +7263,6 @@ maybe_commonize_var (tree decl)
if (DECL_ARTIFICIAL (decl) && !DECL_DECOMPOSITION_P (decl))
return;
- /* These are not output at all. */
- if (consteval_only_p (decl))
- return;
-
/* Static data in a function with comdat linkage also has comdat
linkage. */
if ((TREE_STATIC (decl)
@@ -8758,6 +8754,13 @@ make_rtl_for_nonlocal_decl (tree decl, tree init, const char* asmspec)
{
/* Disable assemble_variable. */
DECL_EXTERNAL (decl) = true;
+ /* Undo make_decl_one_only. */
+ if (DECL_COMDAT_GROUP (decl))
+ {
+ symtab_node *node = symtab_node::get (decl);
+ node->set_comdat_group (NULL);
+ node->dissolve_same_comdat_group_list ();
+ }
return;
}
diff --git a/gcc/testsuite/g++.dg/modules/reflect-1_b.C b/gcc/testsuite/g++.dg/modules/reflect-1_b.C
new file mode 100644
index 00000000000..a3c5b67d09a
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/reflect-1_b.C
@@ -0,0 +1,6 @@
+// PR c++/122785
+// { dg-do compile { target c++26 } }
+// { dg-additional-options "-fmodules -freflection" }
+
+import "reflect-1_a.H";
+using ::S;
diff --git a/gcc/testsuite/g++.dg/modules/reflect-1_a.H b/gcc/testsuite/g++.dg/modules/reflect-1_a.H
new file mode 100644
index 00000000000..025f2e27ea1
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/reflect-1_a.H
@@ -0,0 +1,11 @@
+// PR c++/122785
+// { dg-do compile { target c++26 } }
+// { dg-additional-options "-fmodule-header -freflection" }
+// { dg-module-cmi {} }
+
+struct S {
+ friend S foo();
+ S bar(int);
+};
+inline S s;
+template <typename T> decltype(s.bar(T{})) foo(T);
--
2.52.0
