From: Nathaniel Shead <nathanieloshead@gmail.com>
Date: Sun, 26 Oct 2025 11:27:33 +0000 (+1100)
Subject: c++/modules: Track all static class variables [PR122421]
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=fd5c057c2d01346d69119f88ca94debf27842e4e;p=thirdparty%2Fgcc.git

c++/modules: Track all static class variables [PR122421]

The linker error in the PR is caused because when a static is defined
out of the class body, it doesn't yet have a definition and so
read_var_def (which would otherwise have noted it) never gets called.

This instead moves the responsibility for noting class-scope variables
to read_class_def.

	PR c++/122421

gcc/cp/ChangeLog:

	* module.cc (trees_in::read_var_def): Don't handle class-scope
	variables anymore.
	(trees_in::read_class_def): Handle them here instead.

gcc/testsuite/ChangeLog:

	* g++.dg/modules/inst-6_a.C: New test.
	* g++.dg/modules/inst-6_b.C: New test.

Signed-off-by: Nathaniel Shead <nathanieloshead@gmail.com>
Reviewed-by: Jason Merrill <jason@redhat.com>
---

diff --git a/gcc/cp/module.cc b/gcc/cp/module.cc
index 31f5c8146d6..e0b9efa02b6 100644
--- a/gcc/cp/module.cc
+++ b/gcc/cp/module.cc
@@ -13048,12 +13048,11 @@ trees_in::read_var_def (tree decl, tree maybe_template)
 	  if (DECL_EXPLICIT_INSTANTIATION (decl)
 	      && !DECL_EXTERNAL (decl))
 	    setup_explicit_instantiation_definition_linkage (decl);
-	  if (DECL_IMPLICIT_INSTANTIATION (decl)
-	      || (DECL_EXPLICIT_INSTANTIATION (decl)
-		  && !DECL_EXTERNAL (decl))
-	      || (DECL_CLASS_SCOPE_P (decl)
-		  && !DECL_VTABLE_OR_VTT_P (decl)
-		  && !DECL_TEMPLATE_INFO (decl)))
+	  /* Class static data members are handled in read_class_def.  */
+	  if (!DECL_CLASS_SCOPE_P (decl)
+	      && (DECL_IMPLICIT_INSTANTIATION (decl)
+		  || (DECL_EXPLICIT_INSTANTIATION (decl)
+		      && !DECL_EXTERNAL (decl))))
 	    note_vague_linkage_variable (decl);
 	}
       if (!dyn_init)
@@ -13467,6 +13466,10 @@ trees_in::read_class_def (tree defn, tree maybe_template)
 			DECL_ACCESS (d) = tree_cons (type, access, list);
 		    }
 		}
+
+	      if (TREE_CODE (decl) == VAR_DECL
+		  && TREE_CODE (maybe_template) != TEMPLATE_DECL)
+		note_vague_linkage_variable (decl);
 	    }
 	}
 
diff --git a/gcc/testsuite/g++.dg/modules/inst-6_a.C b/gcc/testsuite/g++.dg/modules/inst-6_a.C
new file mode 100644
index 00000000000..7f35cc161bf
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/inst-6_a.C
@@ -0,0 +1,14 @@
+// PR c++/122421
+// { dg-additional-options "-fmodules" }
+// { dg-module-cmi M }
+
+export module M;
+
+export template <typename T> struct Type {
+  static const int arr[3];
+};
+
+extern template const int Type<double>::arr[3];
+template <typename T> const int Type<T>::arr[] = { 42, 43, 44 };
+
+export Type<int> ti;
diff --git a/gcc/testsuite/g++.dg/modules/inst-6_b.C b/gcc/testsuite/g++.dg/modules/inst-6_b.C
new file mode 100644
index 00000000000..5a8092ccb14
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/inst-6_b.C
@@ -0,0 +1,12 @@
+// PR c++/122421
+// { dg-additional-options "-fmodules" }
+
+import M;
+
+int main() {
+  const int& a = Type<int>::arr[0];
+  const int& b = Type<double>::arr[0];
+}
+
+// { dg-final { scan-assembler {_ZNW1M4TypeIiE3arrE:} } }
+// { dg-final { scan-assembler-not {_ZNW1M4TypeIdE3arrE:} } }