[PATCH] D32838: [libcxx] Make __shared_weak_count VTable consistent across all build configurations

[Eric Fiselier via Phabricator via cfe-commits]

EricWF created this revision.

This patch ensures that `__shared_weak_count` provides a consistent vtable regardless of if RTTI is enabled or if we are targeting a static or shared libc++ build.

This patch is technically ABI breaking, but only for a very specific configuration that neither Apple nor FreeBSD should be shipping.

@dexonsmith @emaste can you confirm that you don't ship builds of libc++ that have both (A) RTTI disabled, and (B) Manually define `_LIBCPP_BUILD_STATIC`?

Note that `_LIBCPP_BUILD_STATIC` is not normally defined when building `libc++.a`, but instead it must be manually provided by the user or the `__config_site`.


https://reviews.llvm.org/D32838

Files:
  include/memory
  src/memory.cpp


Index: src/memory.cpp
===================================================================
--- src/memory.cpp
+++ src/memory.cpp
@@ -123,16 +123,12 @@
     return 0;
 }
 
-#if !defined(_LIBCPP_NO_RTTI) || !defined(_LIBCPP_BUILD_STATIC)
-
 const void*
 __shared_weak_count::__get_deleter(const type_info&) const _NOEXCEPT
 {
-    return 0;
+    return nullptr;
 }
 
-#endif  // _LIBCPP_NO_RTTI
-
 #if !defined(_LIBCPP_HAS_NO_ATOMIC_HEADER)
 
 _LIBCPP_SAFE_STATIC static const std::size_t __sp_mut_count = 16;
Index: include/memory
===================================================================
--- include/memory
+++ include/memory
@@ -3523,13 +3523,7 @@
     long use_count() const _NOEXCEPT {return __shared_count::use_count();}
     __shared_weak_count* lock() _NOEXCEPT;
 
-    // Define the function out only if we build static libc++ without RTTI.
-    // Otherwise we may break clients who need to compile their projects with
-    // -fno-rtti and yet link against a libc++.dylib compiled
-    // without -fno-rtti.
-#if !defined(_LIBCPP_NO_RTTI) || !defined(_LIBCPP_BUILD_STATIC)
     virtual const void* __get_deleter(const type_info&) const _NOEXCEPT;
-#endif
 private:
     virtual void __on_zero_shared_weak() _NOEXCEPT = 0;
 };


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