[libcxx-commits] [PATCH] D65667: [libcxx] Avoid destructor call for error_category singletons

[Chris Bowler via Phabricator via libcxx-commits]

cebowleratibm added inline comments.


================
Comment at: libcxx/src/system_error.cpp:232-238
 const error_category&
 system_category() _NOEXCEPT
 {
-    static __system_error_category s;
-    return s;
+    _LIBCPP_SAFE_STATIC_AFTER_CXX11
+    static SystemErrorHelper s;
+    return s.system_error_category.new_system_error_category;
 }
----------------
Quuxplusone wrote:
> After rebasing, I would expect this would end up looking like
> ```
> const error_category&
> system_category() _NOEXCEPT
> {
>     union U {
>         __system_error_category s;
>         _LIBCPP_CONSTEXPR explicit U() : s() {}
>         ~U() {}  // Too bad this can't be trivial... or can it?
>     };
>     static _LIBCPP_CONSTINIT U u;
>     return u.s;
> }
> ```
> i.e. a very small diff against the left-hand side.
I think the constexpr version will hit this error:

error: constexpr variable cannot have non-literal type 'const U'


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D65667/new/

https://reviews.llvm.org/D65667