[libcxx-commits] [libcxx] [libcxx] Fix ODR violation in iostream. (PR #132125)

[A. Jiang via libcxx-commits]

================
@@ -370,6 +372,8 @@ protected:
     // for the details.
   }
 
+  _LIBCPP_HIDE_FROM_ABI constexpr ios_base(uninitialized_ios) {} 
----------------
frederick-vs-ja wrote:

```suggestion
  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR ios_base(__uninitialized_ios_tag) {} 
```
Ditto for other `constexpr` functions.

https://github.com/llvm/llvm-project/pull/132125