[gcc r14-5826] c++: Allow exporting const-qualified namespace-scope variables [PR99232]

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

https://gcc.gnu.org/g:726723c476800285cfbdfce612cedde4a9a7ad58

commit r14-5826-g726723c476800285cfbdfce612cedde4a9a7ad58
Author: Nathaniel Shead <nathanieloshead@gmail.com>
Date:   Wed Nov 15 20:50:53 2023 +1100

    c++: Allow exporting const-qualified namespace-scope variables [PR99232]
    
    By [basic.link] p3.2.1, a non-template non-volatile const-qualified
    variable is not necessarily internal linkage in a module declaration,
    and rather may have module linkage (or external linkage if it is
    exported, see p4.8).
    
            PR c++/99232
    
    gcc/cp/ChangeLog:
    
            * decl.cc (grokvardecl): Don't mark variables attached to
            modules as internal.
    
    gcc/testsuite/ChangeLog:
    
            * g++.dg/modules/pr99232_a.C: New test.
            * g++.dg/modules/pr99232_b.C: New test.
    
    Signed-off-by: Nathaniel Shead <nathanieloshead@gmail.com>

Diff:
---
 gcc/cp/decl.cc                           |  3 ++-
 gcc/testsuite/g++.dg/modules/pr99232_a.C | 12 ++++++++++++
 gcc/testsuite/g++.dg/modules/pr99232_b.C | 13 +++++++++++++
 3 files changed, 27 insertions(+), 1 deletion(-)

diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
index 16b04ebe0f8..ed1401591fa 100644
--- a/gcc/cp/decl.cc
+++ b/gcc/cp/decl.cc
@@ -11006,7 +11006,8 @@ grokvardecl (tree type,
 			    && (DECL_THIS_EXTERN (decl)
 				|| ! constp
 				|| volatilep
-				|| inlinep));
+				|| inlinep
+				|| module_attach_p ()));
       TREE_STATIC (decl) = ! DECL_EXTERNAL (decl);
     }
   /* Not at top level, only `static' makes a static definition.  */
diff --git a/gcc/testsuite/g++.dg/modules/pr99232_a.C b/gcc/testsuite/g++.dg/modules/pr99232_a.C
new file mode 100644
index 00000000000..097fb5e4403
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/pr99232_a.C
@@ -0,0 +1,12 @@
+// PR c++/99232
+// { dg-additional-options "-fmodules-ts" }
+// { dg-module-cmi pr99232 }
+
+export module pr99232;
+
+export const double lambda{ 1.3 };
+export constexpr int a = 42;
+
+export const double* get_lambda_addr() {
+  return &lambda;
+}
diff --git a/gcc/testsuite/g++.dg/modules/pr99232_b.C b/gcc/testsuite/g++.dg/modules/pr99232_b.C
new file mode 100644
index 00000000000..a36a76fa5b7
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/pr99232_b.C
@@ -0,0 +1,13 @@
+// PR c++/99232
+// { dg-module-do run }
+// { dg-additional-options "-fmodules-ts" }
+
+import pr99232;
+
+double foo() { return lambda * 2.0; }
+static_assert(a == 42);
+
+int main() {
+  if (&lambda != get_lambda_addr())
+    __builtin_abort();
+}