From: Nathaniel Shead <nathanieloshead@gmail.com>
Date: Sat, 15 Nov 2025 04:11:55 +0000 (+1100)
Subject: c++/modules: Keep tracking instantiations of static class variable templates [PR122625]
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=4711901000ab141dbf3995ec4541f9d9a2351472;p=thirdparty%2Fgcc.git

c++/modules: Keep tracking instantiations of static class variable templates [PR122625]

r16-4930-gfd5c057c2d01 ensured that we noted all class-scope variables.
But I also added a clause to 'read_var_def' to skip all class-scope
instantiations, under the mistaken belief that this would be handled in
read_class_def.

But as the testcase shows, read_class_def cannot (and should not)
register instantiations of member variable templates, as when reading
the class it just sees the template declaration.  So this patch
re-enables tracking instantiations of class-scope variable templates.

	PR c++/122625

gcc/cp/ChangeLog:

	* module.cc (trees_in::read_var_def): Also track class-scope
	primary template specialisations.

gcc/testsuite/ChangeLog:

	* g++.dg/modules/inst-7_a.C: New test.
	* g++.dg/modules/inst-7_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 48ee7d1e790..017bacdf223 100644
--- a/gcc/cp/module.cc
+++ b/gcc/cp/module.cc
@@ -13074,8 +13074,10 @@ trees_in::read_var_def (tree decl, tree maybe_template)
 	  if (DECL_EXPLICIT_INSTANTIATION (decl)
 	      && !DECL_EXTERNAL (decl))
 	    setup_explicit_instantiation_definition_linkage (decl);
-	  /* Class static data members are handled in read_class_def.  */
-	  if (!DECL_CLASS_SCOPE_P (decl)
+	  /* Class non-template static members are handled in read_class_def.
+	     But still handle specialisations of member templates.  */
+	  if ((!DECL_CLASS_SCOPE_P (decl)
+	       || primary_template_specialization_p (decl))
 	      && (DECL_IMPLICIT_INSTANTIATION (decl)
 		  || (DECL_EXPLICIT_INSTANTIATION (decl)
 		      && !DECL_EXTERNAL (decl))))
diff --git a/gcc/testsuite/g++.dg/modules/inst-7_a.C b/gcc/testsuite/g++.dg/modules/inst-7_a.C
new file mode 100644
index 00000000000..7489edfa252
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/inst-7_a.C
@@ -0,0 +1,33 @@
+// PR c++/122625
+// { dg-additional-options "-fmodules" }
+// { dg-module-cmi M }
+
+export module M;
+struct integral_constant {
+  void f() const {}
+};
+struct span {
+  template <int> static constexpr integral_constant __v{};
+  template <int, int> static constexpr integral_constant partial{};
+};
+template <int x> constexpr integral_constant span::partial<x, 0>{};
+
+template <typename T>
+struct nested {
+  template <typename U> static const U arr[3];
+};
+template <typename T>
+struct nested<T*> {
+  template <typename U> static const U arr[3];
+};
+template <typename T> template <typename U> const U nested<T>::arr[3] = {};
+template <typename T> template <typename U> const U nested<T*>::arr[3] = {};
+template <typename T> template <typename U> const U nested<T*>::arr<U*>[3] = {};
+
+export inline void format() {
+  span::__v<1>.f();
+  span::partial<5, 0>.f();
+  nested<int>::arr<integral_constant>[0].f();
+  nested<int*>::arr<integral_constant>[0].f();
+  nested<int*>::arr<integral_constant*>[0].f();
+}
diff --git a/gcc/testsuite/g++.dg/modules/inst-7_b.C b/gcc/testsuite/g++.dg/modules/inst-7_b.C
new file mode 100644
index 00000000000..3a49b516bea
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/inst-7_b.C
@@ -0,0 +1,13 @@
+// PR c++/122625
+// { dg-additional-options "-fmodules" }
+
+import M;
+int main() {
+  format();
+}
+
+// { dg-final { scan-assembler {_ZNW1M4span3__vILi1EEE:} } }
+// { dg-final { scan-assembler {_ZNW1M4span7partialILi5ELi0EEE:} } }
+// { dg-final { scan-assembler {_ZNW1M6nestedIiE3arrIS_17integral_constantEE:} } }
+// { dg-final { scan-assembler {_ZNW1M6nestedIPiE3arrIS_17integral_constantEE:} } }
+// { dg-final { scan-assembler {_ZNW1M6nestedIPiE3arrIPS_17integral_constantEE:} } }