Make _LIBCPP_DEPRECATED_ABI_DISABLE_PAIR_TRIVIAL_COPY_CTOR user-settable

[dim]

Summary

In rL275749 the old _LIBCPP_TRIVIAL_PAIR_COPY_CTOR define was replaced
by _LIBCPP_DEPRECATED_ABI_DISABLE_PAIR_TRIVIAL_COPY_CTOR, which is also
auto-detected.

However, it is not overridable by the user, since you cannot use -U or
#undef to get rid of the define after __config was included, at least
not without gross hacks.

In the FreeBSD ports tree we have at least one libc++ consumer that
really needs to turn on the trivial constructor (chromium), see
https://bugs.freebsd.org/214654 for the details. So I would like to
propose making _LIBCPP_DEPRECATED_ABI_DISABLE_PAIR_TRIVIAL_COPY_CTOR
user-settable (to either zero, or nonzero).

[EricWF]

@dim Do you still need this to fix the chromium bug?

[dim]

No, let's drop it. In the FreeBSD ports bug I have posted a patch to use _LIBCPP_ABI_UNSTABLE instead, which appears to work fine. And at some point we'll update to _LIBCPP_ABI_VERSION 2, but not today. :)

include/__config

 // Fix undefined behavior in how __hash_table stores it's pointer types
 #define _LIBCPP_ABI_FIX_UNORDERED_NODE_POINTER_UB
 #define _LIBCPP_ABI_FORWARD_LIST_REMOVE_NODE_POINTER_UB
 #define _LIBCPP_ABI_FIX_UNORDERED_CONTAINER_SIZE_TYPE
 #define _LIBCPP_ABI_VARIADIC_LOCK_GUARD
 #elif _LIBCPP_ABI_VERSION == 1
 // Feature macros for disabling pre ABI v1 features. All of these options
 // are deprecated.
-#if defined(__FreeBSD__)
-#define _LIBCPP_DEPRECATED_ABI_DISABLE_PAIR_TRIVIAL_COPY_CTOR
-#endif
+# if !defined(_LIBCPP_DEPRECATED_ABI_DISABLE_PAIR_TRIVIAL_COPY_CTOR)
+#  if defined(__FreeBSD__)
+#   define _LIBCPP_DEPRECATED_ABI_DISABLE_PAIR_TRIVIAL_COPY_CTOR 1
+#  else
+#   define _LIBCPP_DEPRECATED_ABI_DISABLE_PAIR_TRIVIAL_COPY_CTOR 0
+#  endif
+# endif
 #endif
 
 #ifdef _LIBCPP_TRIVIAL_PAIR_COPY_CTOR
 #error "_LIBCPP_TRIVIAL_PAIR_COPY_CTOR" is no longer supported. \
        use _LIBCPP_DEPRECATED_ABI_DISABLE_PAIR_TRIVIAL_COPY_CTOR instead
 #endif
 
 #define _LIBCPP_CONCAT1(_LIBCPP_X,_LIBCPP_Y) _LIBCPP_X##_LIBCPP_Y

include/utility

 
 struct _LIBCPP_TYPE_VIS_ONLY piecewise_construct_t { };
 #if defined(_LIBCPP_HAS_NO_CONSTEXPR) || defined(_LIBCPP_BUILDING_UTILITY)
 extern const piecewise_construct_t piecewise_construct;// = piecewise_construct_t();
 #else
 constexpr piecewise_construct_t piecewise_construct = piecewise_construct_t();
 #endif
 
-#if defined(_LIBCPP_DEPRECATED_ABI_DISABLE_PAIR_TRIVIAL_COPY_CTOR)
+#if _LIBCPP_DEPRECATED_ABI_DISABLE_PAIR_TRIVIAL_COPY_CTOR != 0
 struct __non_trivially_copyable_base {
   _LIBCPP_CONSTEXPR _LIBCPP_INLINE_VISIBILITY
   __non_trivially_copyable_base() _NOEXCEPT {}
   _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
   __non_trivially_copyable_base(__non_trivially_copyable_base const&) _NOEXCEPT {}
 };
 #endif
 
 template <class _T1, class _T2>
 struct _LIBCPP_TYPE_VIS_ONLY pair
-#if defined(_LIBCPP_DEPRECATED_ABI_DISABLE_PAIR_TRIVIAL_COPY_CTOR)
+#if _LIBCPP_DEPRECATED_ABI_DISABLE_PAIR_TRIVIAL_COPY_CTOR != 0
 : private __non_trivially_copyable_base
 #endif
 {
     typedef _T1 first_type;
     typedef _T2 second_type;
 
     _T1 first;
     _T2 second;

test/libcxx/utilities/utility/pairs/pairs.pair/non_trivial_copy_move_ABI.pass.cpp

 
 // Test that we properly provide the trivial copy operations by default.
 
 // FreeBSD provides the old ABI. This test checks the new ABI so we need
 // to manually turn it on.
 #undef _LIBCPP_ABI_UNSTABLE
 #undef _LIBCPP_ABI_VERSION
 #define _LIBCPP_ABI_VERSION 1
-#define _LIBCPP_DEPRECATED_ABI_DISABLE_PAIR_TRIVIAL_COPY_CTOR
+#define _LIBCPP_DEPRECATED_ABI_DISABLE_PAIR_TRIVIAL_COPY_CTOR 1
 
 #include <utility>
 #include <type_traits>
 #include <cstdlib>
 #include <cassert>
 
 #include "test_macros.h"
 
-#if !defined(_LIBCPP_DEPRECATED_ABI_DISABLE_PAIR_TRIVIAL_COPY_CTOR)
+#if _LIBCPP_DEPRECATED_ABI_DISABLE_PAIR_TRIVIAL_COPY_CTOR == 0
 #error trivial ctor ABI macro defined
 #endif
 
 template <class T>
 struct HasNonTrivialABI : std::integral_constant<bool,
     !std::is_trivially_destructible<T>::value
     || (std::is_copy_constructible<T>::value && !std::is_trivially_copy_constructible<T>::value)
 #if TEST_STD_VER >= 11

test/libcxx/utilities/utility/pairs/pairs.pair/trivial_copy_move_ABI.pass.cpp

 
 #include <utility>
 #include <type_traits>
 #include <cstdlib>
 #include <cassert>
 
 #include "test_macros.h"
 
-#if defined(_LIBCPP_DEPRECATED_ABI_DISABLE_PAIR_TRIVIAL_COPY_CTOR)
+#if _LIBCPP_DEPRECATED_ABI_DISABLE_PAIR_TRIVIAL_COPY_CTOR != 0
 #error Non-trivial ctor ABI macro defined
 #endif
 
 template <class T>
 struct HasTrivialABI : std::integral_constant<bool,
     std::is_trivially_destructible<T>::value
     && (!std::is_copy_constructible<T>::value || std::is_trivially_copy_constructible<T>::value)
 #if TEST_STD_VER >= 11

test/std/utilities/utility/pairs/pairs.pair/trivial_copy_move.pass.cpp

struct Dummy {
   Dummy(Dummy &&) = default;
 };
 
 int main()
 {
     typedef std::pair<int, short> P;
     {
         static_assert(std::is_copy_constructible<P>::value, "");
-#if !defined(_LIBCPP_DEPRECATED_ABI_DISABLE_PAIR_TRIVIAL_COPY_CTOR)
+#if _LIBCPP_DEPRECATED_ABI_DISABLE_PAIR_TRIVIAL_COPY_CTOR == 0
         static_assert(std::is_trivially_copy_constructible<P>::value, "");
 #endif
     }
 #if TEST_STD_VER >= 11
     {
         static_assert(std::is_move_constructible<P>::value, "");
-#if !defined(_LIBCPP_DEPRECATED_ABI_DISABLE_PAIR_TRIVIAL_COPY_CTOR)
+#if _LIBCPP_DEPRECATED_ABI_DISABLE_PAIR_TRIVIAL_COPY_CTOR == 0
         static_assert(std::is_trivially_move_constructible<P>::value, "");
 #endif
     }
     {
         using P1 = std::pair<Dummy, int>;
         static_assert(!std::is_copy_constructible<P1>::value, "");
         static_assert(!std::is_trivially_copy_constructible<P1>::value, "");
         static_assert(std::is_move_constructible<P1>::value, "");
-#if !defined(_LIBCPP_DEPRECATED_ABI_DISABLE_PAIR_TRIVIAL_COPY_CTOR)
+#if _LIBCPP_DEPRECATED_ABI_DISABLE_PAIR_TRIVIAL_COPY_CTOR == 0
         static_assert(std::is_trivially_move_constructible<P1>::value, "");
 #endif
     }
 #endif
 }