[gcc r14-8451] c++: Emit definitions of ODR-used static members imported from modules [PR112899]

[Nathaniel Shead <nshead@gcc.gnu.org>]

https://gcc.gnu.org/g:a0dde47f84f17cbe7fa2fb41c14c5a2db8c4d63a

commit r14-8451-ga0dde47f84f17cbe7fa2fb41c14c5a2db8c4d63a
Author: Nathaniel Shead <nathanieloshead@gmail.com>
Date:   Wed Jan 3 09:27:06 2024 +1100

    c++: Emit definitions of ODR-used static members imported from modules [PR112899]
    
    Static data members marked 'inline' should be emitted in TUs where they
    are ODR-used.  We need to make sure that inlines imported from modules
    are correctly added to the 'pending_statics' map so that they get
    emitted if needed, otherwise the attached testcase fails to link.
    
            PR c++/112899
    
    gcc/cp/ChangeLog:
    
            * cp-tree.h (note_variable_template_instantiation): Rename to...
            (note_vague_linkage_variable): ...this.
            * decl2.cc (note_variable_template_instantiation): Rename to...
            (note_vague_linkage_variable): ...this.
            * pt.cc (instantiate_decl): Rename usage of above function.
            * module.cc (trees_in::read_var_def): Remember pending statics
            that we stream in.
    
    gcc/testsuite/ChangeLog:
    
            * g++.dg/modules/init-4_a.C: New test.
            * g++.dg/modules/init-4_b.C: New test.
            * g++.dg/modules/init-6_a.H: New test.
            * g++.dg/modules/init-6_b.C: New test.
    
    Signed-off-by: Nathaniel Shead <nathanieloshead@gmail.com>
    Reviewed-by: Patrick Palka <ppalka@redhat.com>
    Reviewed-by: Jason Merrill <jason@redhat.com

Diff:
---
 gcc/cp/cp-tree.h                        |  2 +-
 gcc/cp/decl2.cc                         |  4 ++--
 gcc/cp/module.cc                        |  5 +++++
 gcc/cp/pt.cc                            |  2 +-
 gcc/testsuite/g++.dg/modules/init-4_a.C |  9 +++++++++
 gcc/testsuite/g++.dg/modules/init-4_b.C | 11 +++++++++++
 gcc/testsuite/g++.dg/modules/init-6_a.H | 20 ++++++++++++++++++++
 gcc/testsuite/g++.dg/modules/init-6_b.C |  9 +++++++++
 8 files changed, 58 insertions(+), 4 deletions(-)

diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
index 60e6dafc5494..f46b448ce0d2 100644
--- a/gcc/cp/cp-tree.h
+++ b/gcc/cp/cp-tree.h
@@ -7151,7 +7151,7 @@ extern tree maybe_get_tls_wrapper_call		(tree);
 extern void mark_needed				(tree);
 extern bool decl_needed_p			(tree);
 extern void note_vague_linkage_fn		(tree);
-extern void note_variable_template_instantiation (tree);
+extern void note_vague_linkage_variable		(tree);
 extern tree build_artificial_parm		(tree, tree, tree);
 extern bool possibly_inlined_p			(tree);
 extern int parm_index                           (tree);
diff --git a/gcc/cp/decl2.cc b/gcc/cp/decl2.cc
index 91d4e2e5ea4c..f569d4045ecc 100644
--- a/gcc/cp/decl2.cc
+++ b/gcc/cp/decl2.cc
@@ -947,10 +947,10 @@ note_vague_linkage_fn (tree decl)
   vec_safe_push (deferred_fns, decl);
 }
 
-/* As above, but for variable template instantiations.  */
+/* As above, but for variables.  */
 
 void
-note_variable_template_instantiation (tree decl)
+note_vague_linkage_variable (tree decl)
 {
   vec_safe_push (pending_statics, decl);
 }
diff --git a/gcc/cp/module.cc b/gcc/cp/module.cc
index f26b2265bce5..6176801b7a74 100644
--- a/gcc/cp/module.cc
+++ b/gcc/cp/module.cc
@@ -11789,6 +11789,11 @@ trees_in::read_var_def (tree decl, tree maybe_template)
 	  DECL_INITIALIZED_P (decl) = true;
 	  if (maybe_dup && DECL_INITIALIZED_BY_CONSTANT_EXPRESSION_P (maybe_dup))
 	    DECL_INITIALIZED_BY_CONSTANT_EXPRESSION_P (decl) = true;
+	  if (DECL_IMPLICIT_INSTANTIATION (decl)
+	      || (DECL_CLASS_SCOPE_P (decl)
+		  && !DECL_VTABLE_OR_VTT_P (decl)
+		  && !DECL_TEMPLATE_INFO (decl)))
+	    note_vague_linkage_variable (decl);
 	}
       DECL_INITIAL (decl) = init;
       if (!dyn_init)
diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index 74013533b0f6..f5bf159a879f 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -27300,7 +27300,7 @@ instantiate_decl (tree d, bool defer_ok, bool expl_inst_class_mem_p)
     {
       set_instantiating_module (d);
       if (variable_template_p (gen_tmpl))
-	note_variable_template_instantiation (d);
+	note_vague_linkage_variable (d);
       instantiate_body (td, args, d, false);
     }
 
diff --git a/gcc/testsuite/g++.dg/modules/init-4_a.C b/gcc/testsuite/g++.dg/modules/init-4_a.C
new file mode 100644
index 000000000000..e0eb97b474e6
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/init-4_a.C
@@ -0,0 +1,9 @@
+// PR c++/112899
+// { dg-additional-options "-fmodules-ts" }
+// { dg-module-cmi M }
+
+export module M;
+
+export struct A {
+  static constexpr int x = -1;
+};
diff --git a/gcc/testsuite/g++.dg/modules/init-4_b.C b/gcc/testsuite/g++.dg/modules/init-4_b.C
new file mode 100644
index 000000000000..d28017a1d143
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/init-4_b.C
@@ -0,0 +1,11 @@
+// PR c++/112899
+// { dg-module-do run }
+// { dg-additional-options "-fmodules-ts" }
+
+import M;
+
+int main() {
+  const int& x = A::x;
+  if (x != -1)
+    __builtin_abort();
+}
diff --git a/gcc/testsuite/g++.dg/modules/init-6_a.H b/gcc/testsuite/g++.dg/modules/init-6_a.H
new file mode 100644
index 000000000000..1c3fe4535d40
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/init-6_a.H
@@ -0,0 +1,20 @@
+// { dg-additional-options "-fmodule-header" }
+// { dg-module-cmi {} }
+
+template <bool _DecOnly>
+struct __from_chars_alnum_to_val_table {
+  static inline int value = 42;
+};
+
+inline unsigned char
+__from_chars_alnum_to_val() {
+  return __from_chars_alnum_to_val_table<false>::value;
+}
+
+template <bool Foo>
+static inline int nonclass_value = 42;
+
+inline unsigned char
+get_nonclass_val() {
+  return nonclass_value<false>;
+}
diff --git a/gcc/testsuite/g++.dg/modules/init-6_b.C b/gcc/testsuite/g++.dg/modules/init-6_b.C
new file mode 100644
index 000000000000..d704968ec375
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/init-6_b.C
@@ -0,0 +1,9 @@
+// { dg-module-do link }
+// { dg-additional-options "-fmodules-ts" }
+
+import "init-6_a.H";
+
+int main() {
+  __from_chars_alnum_to_val();
+  get_nonclass_val();
+}