On 9/23/24 7:43 PM, Nathaniel Shead wrote:
This patch intends no change in functionality apart from the mangling difference noted; more tests are in patch 4 of this series, which adds a way to actually check what the linkage of decl_linkage provides more directly.Bootstrapped and regtested on x86_64-pc-linux-gnu, OK for trunk? -- >8 -- Currently modules code uses a variety of ad-hoc methods to attempt to determine whether an entity has internal linkage, which leads to inconsistencies and some correctness issues as different edge cases are neglected. While investigating this I discovered 'decl_linkage', but it doesn't seem to have been updated to account for the C++11 clarification that all entities declared in an anonymous namespace are internal. I'm not convinced that even in C++98 it was intended that e.g. types in anonymous namespaces should be external, but some tests in the testsuite rely on this, so for compatibility I restricted those modifications to C++11 and later. This should have relatively minimal impact as not much seems to actually rely on decl_linkage, but does change the mangling of symbols in anonymous namespaces slightly. Previously, we had namespace { int x; // mangled as '_ZN12_GLOBAL__N_11xE' static int y; // mangled as '_ZN12_GLOBAL__N_1L1yE' } but with this patch the x is now mangled like y (with the extra 'L'). For contrast, Clang currently mangles neither x nor y with the 'L'. Since this only affects internal-linkage entities I don't believe this should break ABI in any observable fashion. gcc/cp/ChangeLog: * name-lookup.cc (do_namespace_alias): Propagate TREE_PUBLIC for namespace aliases. * tree.cc (decl_linkage): Update rules for C++11. gcc/testsuite/ChangeLog: * g++.dg/modules/mod-sym-4.C: Update test to account for non-static internal-linkage variables new mangling. Signed-off-by: Nathaniel Shead <nathanielosh...@gmail.com> --- gcc/cp/name-lookup.cc | 1 + gcc/cp/tree.cc | 92 +++++++++++++++--------- gcc/testsuite/g++.dg/modules/mod-sym-4.C | 4 +- 3 files changed, 60 insertions(+), 37 deletions(-) diff --git a/gcc/cp/name-lookup.cc b/gcc/cp/name-lookup.cc index c7a693e02d5..50e169eca43 100644 --- a/gcc/cp/name-lookup.cc +++ b/gcc/cp/name-lookup.cc @@ -6610,6 +6610,7 @@ do_namespace_alias (tree alias, tree name_space) DECL_NAMESPACE_ALIAS (alias) = name_space; DECL_EXTERNAL (alias) = 1; DECL_CONTEXT (alias) = FROB_CONTEXT (current_scope ()); + TREE_PUBLIC (alias) = TREE_PUBLIC (DECL_CONTEXT (alias)); set_originating_module (alias);pushdecl (alias);diff --git a/gcc/cp/tree.cc b/gcc/cp/tree.cc index f43febed124..28e14295de4 100644 --- a/gcc/cp/tree.cc +++ b/gcc/cp/tree.cc @@ -5840,7 +5840,7 @@ char_type_p (tree type) || same_type_p (type, wchar_type_node)); }-/* Returns the kind of linkage associated with the indicated DECL. Th+/* Returns the kind of linkage associated with the indicated DECL. The value returned is as specified by the language standard; it is independent of implementation details regarding template instantiation, etc. For example, it is possible that a declaration @@ -5857,53 +5857,75 @@ decl_linkage (tree decl) linkage first, and then transform that into a concrete implementation. */- /* Things that don't have names have no linkage. */- if (!DECL_NAME (decl)) - return lk_none; + /* An explicit type alias has no linkage. */ + if (TREE_CODE (decl) == TYPE_DECL + && !DECL_IMPLICIT_TYPEDEF_P (decl) + && !DECL_SELF_REFERENCE_P (decl)) + { + /* But this could be a typedef name for linkage purposes, in which + case we're interested in the linkage of the main decl. */
Perhaps we should move is_naming_typedef_decl out of dwarf2out.cc... Anyway, the patch is OK. Jason
