[libcxx-commits] [PATCH] D97802: [libc++] Fix incorrect typeinfo comparison on ARM64

Louis Dionne via Phabricator via libcxx-commits libcxx-commits at lists.llvm.org
Tue Mar 2 13:23:07 PST 2021

ldionne created this revision.
Herald added subscribers: jkorous, kristof.beyls.
ldionne requested review of this revision.
Herald added a project: libc++.
Herald added a subscriber: libcxx-commits.
Herald added a reviewer: libc++.

We are supposed to use deep string comparison when either the LHS or the
RHS can't be guaranteed to be unique, however the current implementation
was using deep comparison only when both the LHS and the RHS couldn't be
guaranteed to be unique.

See https://lists.llvm.org/pipermail/libcxx-dev/2020-December/001060.html.

  rG LLVM Github Monorepo



Index: libcxx/include/typeinfo
--- libcxx/include/typeinfo
+++ libcxx/include/typeinfo
@@ -248,13 +248,13 @@
     static bool __eq(__type_name_t __lhs, __type_name_t __rhs) _NOEXCEPT {
       if (__lhs == __rhs)
         return true;
-      if (__is_type_name_unique(__lhs, __rhs))
+      if (__is_type_name_unique(__lhs) && __is_type_name_unique(__rhs))
         return false;
       return __builtin_strcmp(__type_name_to_string(__lhs), __type_name_to_string(__rhs)) == 0;
     static bool __lt(__type_name_t __lhs, __type_name_t __rhs) _NOEXCEPT {
-      if (__is_type_name_unique(__lhs, __rhs))
+      if (__is_type_name_unique(__lhs) && __is_type_name_unique(__rhs))
         return __lhs < __rhs;
       return __builtin_strcmp(__type_name_to_string(__lhs), __type_name_to_string(__rhs)) < 0;
@@ -269,10 +269,6 @@
     static bool __is_type_name_unique(__type_name_t __lhs) _NOEXCEPT {
       return !(__lhs & __non_unique_rtti_bit::value);
-    static bool __is_type_name_unique(__type_name_t __lhs, __type_name_t __rhs) _NOEXCEPT {
-      return !((__lhs & __rhs) & __non_unique_rtti_bit::value);
-    }

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