[PATCH] c++/modules: Fix ICE when writing nontrivial variable initializers

[Nathaniel Shead <nathanieloshead@gmail.com>]

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

-- >8 --

The attached testcase Patrick found in PR c++/112899 ICEs because it is
attempting to write a variable initializer that is no longer in the
static_aggregates map.

The issue is that, for non-header modules, the loop in
c_parse_final_cleanups prunes the static_aggregates list, which means
that by the time we get to emitting module information those
initialisers have been lost.

However, we don't actually need to write non-trivial initialisers for
non-header modules, because they've already been emitted as part of the
module TU itself.  Instead let's just only write the initializers from
header modules (which skipped writing them in c_parse_final_cleanups).

gcc/cp/ChangeLog:

	* module.cc (trees_out::write_var_def): Only write initializers
	in header modules.

gcc/testsuite/ChangeLog:

	* g++.dg/modules/init-5_a.C: New test.
	* g++.dg/modules/init-5_b.C: New test.

Signed-off-by: Nathaniel Shead <nathanieloshead@gmail.com>
---
 gcc/cp/module.cc                        |  3 ++-
 gcc/testsuite/g++.dg/modules/init-5_a.C |  9 +++++++++
 gcc/testsuite/g++.dg/modules/init-5_b.C | 10 ++++++++++
 3 files changed, 21 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/g++.dg/modules/init-5_a.C
 create mode 100644 gcc/testsuite/g++.dg/modules/init-5_b.C

diff --git a/gcc/cp/module.cc b/gcc/cp/module.cc
index 14818131a70..82b61a2c2ad 100644
--- a/gcc/cp/module.cc
+++ b/gcc/cp/module.cc
@@ -11707,7 +11707,8 @@ trees_out::write_var_def (tree decl)
     {
       tree dyn_init = NULL_TREE;
 
-      if (DECL_NONTRIVIALLY_INITIALIZED_P (decl))
+      /* We only need to write initializers in header modules.  */
+      if (header_module_p () && DECL_NONTRIVIALLY_INITIALIZED_P (decl))
 	{
 	  dyn_init = value_member (decl,
 				   CP_DECL_THREAD_LOCAL_P (decl)
diff --git a/gcc/testsuite/g++.dg/modules/init-5_a.C b/gcc/testsuite/g++.dg/modules/init-5_a.C
new file mode 100644
index 00000000000..466b120b5a0
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/init-5_a.C
@@ -0,0 +1,9 @@
+// { dg-additional-options "-fmodules-ts" }
+// { dg-module-cmi M }
+
+export module M;
+
+export struct A {
+  static int f() { return -1; }
+  static inline int x = f();
+};
diff --git a/gcc/testsuite/g++.dg/modules/init-5_b.C b/gcc/testsuite/g++.dg/modules/init-5_b.C
new file mode 100644
index 00000000000..40973cc6936
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/init-5_b.C
@@ -0,0 +1,10 @@
+// { dg-module-do run }
+// { dg-additional-options "-fmodules-ts" }
+
+import M;
+
+int main() {
+  const int& x = A::x;
+  if (x != -1)
+    __builtin_abort();
+}
-- 
2.43.0