[libcxx-commits] [libcxx] [libcxx][string] Allow fancy pointers in basic_string (PR #199264)

[A. Jiang via libcxx-commits]

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@@ -878,16 +880,91 @@ private:
 
   static_assert(sizeof(__short) == (sizeof(value_type) * (__min_cap + 1)), "__short has an unexpected size.");
 
-  union __rep {
+  template <typename _LongT, typename = void>
+  union __rep_t {
     __short __s;
-    __long __l;
+    _LongT __l;
 
-    __rep() = default;
-    _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 __rep(__short __r) : __s(__r) {}
-    _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 __rep(__long __r) : __l(__r) {}
-    _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 __rep(__uninitialized_tag) {}
+    _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 void __begin_long_lifetime() {}
+
+    __rep_t() = default;
+    _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 __rep_t(__short __r) : __s(__r) {}
+    _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 __rep_t(_LongT __r) : __l(__r) {}
+    _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 __rep_t(__uninitialized_tag) {}
   };
 
+  template <typename _LongT>
+  union __rep_t<_LongT,
+                typename std::enable_if<!is_trivially_constructible<_LongT>::value ||
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frederick-vs-ja wrote:

Let's use `__enable_if_t` here. Also, we shouldn't use `std::` for non-function components unless necessary.

https://github.com/llvm/llvm-project/pull/199264