[PATCH] c++/modules: Stream unmergeable temporaries by value again [PR114856]

[Nathaniel Shead <nathanieloshead@gmail.com>]

Bootstrapped and regtested on x86_64-pc-linux-gnu, OK for trunk/14.2?

Another alternative would be to stream such !DECL_NAME temporaries with
a merge key of MK_unique rather than attempting to find the matching
(nonexistant) field of the class context.

-- >8 --

In r14-9266-g2823b4d96d9ec4 I gave all temporary vars a DECL_CONTEXT,
including those at namespace or global scope, so that they could be
properly merged across importers.  However, not all of these temporary
vars are actually supposed to be mergeable.

For instance, in the attached testcase we have an unnamed temporary var
used in the NSDMI of a class member, which cannot properly merged -- but
it also doesn't need to be, as it'll be thrown away when the class type
itself is merged anyway.

This patch reverts the change made above and instead makes a weaker
adjustment that only causes temporary vars with linkage have a
DECL_CONTEXT to merge from.  This way these unnamed, "unmergeable"
temporaries are properly streamed by value again.

	PR c++/114856

gcc/cp/ChangeLog:

	* call.cc (make_temporary_var_for_ref_to_temp): Set context for
	temporaries with linkage.
	* init.cc (create_temporary_var): Revert to only set context
	when in a function decl.

gcc/testsuite/ChangeLog:

	* g++.dg/modules/pr114856.h: New test.
	* g++.dg/modules/pr114856_a.H: New test.
	* g++.dg/modules/pr114856_b.C: New test.

Signed-off-by: Nathaniel Shead <nathanieloshead@gmail.com>
---
 gcc/cp/call.cc                            |  1 +
 gcc/cp/init.cc                            |  2 +-
 gcc/testsuite/g++.dg/modules/pr114856.h   | 12 ++++++++++++
 gcc/testsuite/g++.dg/modules/pr114856_a.H |  5 +++++
 gcc/testsuite/g++.dg/modules/pr114856_b.C |  5 +++++
 5 files changed, 24 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/g++.dg/modules/pr114856.h
 create mode 100644 gcc/testsuite/g++.dg/modules/pr114856_a.H
 create mode 100644 gcc/testsuite/g++.dg/modules/pr114856_b.C

diff --git a/gcc/cp/call.cc b/gcc/cp/call.cc
index dbdd7c29fe8..3b8889ac301 100644
--- a/gcc/cp/call.cc
+++ b/gcc/cp/call.cc
@@ -13799,6 +13799,7 @@ make_temporary_var_for_ref_to_temp (tree decl, tree type)
 
       tree name = mangle_ref_init_variable (decl);
       DECL_NAME (var) = name;
+      DECL_CONTEXT (var) = current_scope ();
       SET_DECL_ASSEMBLER_NAME (var, name);
     }
   else
diff --git a/gcc/cp/init.cc b/gcc/cp/init.cc
index a93ce00800c..e758a8c8568 100644
--- a/gcc/cp/init.cc
+++ b/gcc/cp/init.cc
@@ -4287,7 +4287,7 @@ create_temporary_var (tree type)
   TREE_USED (decl) = 1;
   DECL_ARTIFICIAL (decl) = 1;
   DECL_IGNORED_P (decl) = 1;
-  DECL_CONTEXT (decl) = current_scope ();
+  DECL_CONTEXT (decl) = current_function_decl;
 
   return decl;
 }
diff --git a/gcc/testsuite/g++.dg/modules/pr114856.h b/gcc/testsuite/g++.dg/modules/pr114856.h
new file mode 100644
index 00000000000..b1a3c2cd834
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/pr114856.h
@@ -0,0 +1,12 @@
+// PR c++/114856
+
+#include <initializer_list>
+struct A {
+  ~A();
+};
+struct V {
+  V(std::initializer_list<A>);
+};
+struct data {
+  V v{{}};
+};
diff --git a/gcc/testsuite/g++.dg/modules/pr114856_a.H b/gcc/testsuite/g++.dg/modules/pr114856_a.H
new file mode 100644
index 00000000000..6195277dbde
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/pr114856_a.H
@@ -0,0 +1,5 @@
+// PR c++/114856
+// { dg-additional-options "-fmodule-header" }
+// { dg-module-cmi {} }
+
+#include "pr114856.h"
diff --git a/gcc/testsuite/g++.dg/modules/pr114856_b.C b/gcc/testsuite/g++.dg/modules/pr114856_b.C
new file mode 100644
index 00000000000..f81dc8b81d5
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/pr114856_b.C
@@ -0,0 +1,5 @@
+// PR c++/114856
+// { dg-additional-options "-fmodules-ts" }
+
+#include "pr114856.h"
+import "pr114856_a.H";
-- 
2.43.2