From f062a6b7985fcee82e02b626aada4e0824850bd0 Mon Sep 17 00:00:00 2001 From: Nathaniel Shead Date: Thu, 16 Oct 2025 22:51:23 +1100 Subject: [PATCH] c++: Don't constrain template visibility using no-linkage variables [PR122253] When finding the minimal visibility of a template, any reference to a dependent automatic variable will cause the instantiation to be marked as internal linkage. However, when processing the template decl we don't yet know whether that should actually be the case, as a given instantiation may not require referencing the local decl in its mangling. This patch fixes the issue by checking for no-linkage decls first, in which case we just constrain using the type of the entity. We can't use a check for lk_external/lk_internal in the other cases, as instantiations referring to internal types can still have external linkage as determined by the language, but should still constrain the visibility of any declarations that refer to them. PR c++/122253 gcc/cp/ChangeLog: * decl2.cc (min_vis_expr_r): Don't mark no-linkage declarations as VISIBILITY_ANON. gcc/testsuite/ChangeLog: * g++.dg/modules/internal-16.C: New test. Signed-off-by: Nathaniel Shead Reviewed-by: Patrick Palka Reviewed-by: Jason Merrill --- gcc/cp/decl2.cc | 7 ++++- gcc/testsuite/g++.dg/modules/internal-16.C | 30 ++++++++++++++++++++++ 2 files changed, 36 insertions(+), 1 deletion(-) create mode 100644 gcc/testsuite/g++.dg/modules/internal-16.C diff --git a/gcc/cp/decl2.cc b/gcc/cp/decl2.cc index 0073f83a10c..9e135af41b3 100644 --- a/gcc/cp/decl2.cc +++ b/gcc/cp/decl2.cc @@ -2885,7 +2885,12 @@ min_vis_expr_r (tree *tp, int */*walk_subtrees*/, void *data) break; } addressable: - if (! TREE_PUBLIC (t)) + if (decl_linkage (t) == lk_none) + tpvis = type_visibility (TREE_TYPE (t)); + /* Decls that have had their visibility constrained will report + as external linkage, but we still want to transitively constrain + if we refer to them, so just check TREE_PUBLIC instead. */ + else if (!TREE_PUBLIC (t)) tpvis = VISIBILITY_ANON; else tpvis = DECL_VISIBILITY (t); diff --git a/gcc/testsuite/g++.dg/modules/internal-16.C b/gcc/testsuite/g++.dg/modules/internal-16.C new file mode 100644 index 00000000000..4a928ae801b --- /dev/null +++ b/gcc/testsuite/g++.dg/modules/internal-16.C @@ -0,0 +1,30 @@ +// PR c++/122253 +// { dg-additional-options "-fmodules -Wtemplate-names-tu-local" } + +export module M; + +template struct ic {}; +struct S { + constexpr operator int() const { return 5; } + constexpr int operator&() const { return 8; } +}; + +template inline void a(T) { + T a; + static T b; + ic{}; + ic{}; + ic<&a>{}; + ic<&b>{}; +} + +template inline auto b(T x) { + return [&](auto y) { + return [=](auto z) { + return ic<(int)x + (int)&y + (int)z>{}; + }; + }; +} + +template void a(S); +ic<5 + 8 + 5> x = b(S{})(S{})(S{}); -- 2.47.3