From 933f0c20d4ce1dba85e85d9d117cfd9f5376a945 Mon Sep 17 00:00:00 2001
From: Jakub Jelinek <jakub@redhat.com>
Date: Fri, 10 Jan 2025 10:31:12 +0100
Subject: c++: Fix up modules handling of namespace scope structured bindings

With the following patch I actually get a simple namespace scope structured
binding working with modules.

The core_vals change ensure we actually save/restore DECL_VALUE_EXPR even
for namespace scope vars, the get_merge_kind is based on the assumption
that structured bindings are always unique, one can't redeclare them and
without it we really ICE because their base vars have no name.

2025-01-10  Jakub Jelinek  <jakub@redhat.com>

	* module.cc (trees_out::core_vals): Note DECL_VALUE_EXPR even for
	vars outside of functions.
	(trees_in::core_vals): Read in DECL_VALUE_EXPR even for vars outside
	of functions.
	(trees_out::get_merge_kind): Make DECL_DECOMPOSITION_P MK_unique.

	* g++.dg/modules/decomp-2_b.C: New test.
	* g++.dg/modules/decomp-2_a.H: New file.
---
 gcc/cp/module.cc                          | 21 +++++++++++++++++++--
 gcc/testsuite/g++.dg/modules/decomp-2_a.H | 11 +++++++++++
 gcc/testsuite/g++.dg/modules/decomp-2_b.C | 11 +++++++++++
 3 files changed, 41 insertions(+), 2 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/modules/decomp-2_a.H
 create mode 100644 gcc/testsuite/g++.dg/modules/decomp-2_b.C

(limited to 'gcc')

diff --git a/gcc/cp/module.cc b/gcc/cp/module.cc
index fec8206..7288c46 100644
--- a/gcc/cp/module.cc
+++ b/gcc/cp/module.cc
@@ -6318,7 +6318,11 @@ trees_out::core_vals (tree t)
     case VAR_DECL:
       if (DECL_CONTEXT (t)
 	  && TREE_CODE (DECL_CONTEXT (t)) != FUNCTION_DECL)
-	break;
+	{
+	  if (DECL_HAS_VALUE_EXPR_P (t))
+	    WT (DECL_VALUE_EXPR (t));
+	  break;
+	}
       /* FALLTHROUGH  */
 
     case RESULT_DECL:
@@ -6848,7 +6852,14 @@ trees_in::core_vals (tree t)
     case VAR_DECL:
       if (DECL_CONTEXT (t)
 	  && TREE_CODE (DECL_CONTEXT (t)) != FUNCTION_DECL)
-	break;
+	{
+	  if (DECL_HAS_VALUE_EXPR_P (t))
+	    {
+	      tree val = tree_node ();
+	      SET_DECL_VALUE_EXPR (t, val);
+	    }
+	  break;
+	}
       /* FALLTHROUGH  */
 
     case RESULT_DECL:
@@ -10990,6 +11001,12 @@ trees_out::get_merge_kind (tree decl, depset *dep)
 		break;
 	      }
 
+	    if (DECL_DECOMPOSITION_P (decl))
+	      {
+		mk = MK_unique;
+		break;
+	      }
+
 	    if (IDENTIFIER_ANON_P (DECL_NAME (decl)))
 	      {
 		if (RECORD_OR_UNION_TYPE_P (ctx))
diff --git a/gcc/testsuite/g++.dg/modules/decomp-2_a.H b/gcc/testsuite/g++.dg/modules/decomp-2_a.H
new file mode 100644
index 0000000..df2d82a
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/decomp-2_a.H
@@ -0,0 +1,11 @@
+// { dg-additional-options -fmodule-header }
+// { dg-module-cmi {} }
+
+struct A {
+  int a, b, c;
+};
+
+namespace {
+A d = { 1, 2, 3 };
+auto [a, b, c] = d;
+}
diff --git a/gcc/testsuite/g++.dg/modules/decomp-2_b.C b/gcc/testsuite/g++.dg/modules/decomp-2_b.C
new file mode 100644
index 0000000..0353c8e
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/decomp-2_b.C
@@ -0,0 +1,11 @@
+// { dg-do run }
+// { dg-additional-options "-fmodules-ts" }
+
+import "decomp-2_a.H";
+
+int
+main ()
+{
+  if (a != 1 || b != 2 || c != 3)
+    __builtin_abort ();
+}
-- 
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