[libcxx-commits] [libcxx] [libc++] Refactor iostream.cpp (PR #121116)

[Louis Dionne via libcxx-commits]

================
@@ -8,91 +8,67 @@
 
 #include "std_stream.h"
 #include <__locale>
-#include <new>
-#include <string>
-
-#define _str(s) #s
-#define str(s) _str(s)
-#define _LIBCPP_ABI_NAMESPACE_STR str(_LIBCPP_ABI_NAMESPACE)
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-alignas(istream) _LIBCPP_EXPORTED_FROM_ABI char cin[sizeof(istream)]
-#if defined(_LIBCPP_ABI_MICROSOFT) && defined(__clang__)
-    __asm__("?cin@" _LIBCPP_ABI_NAMESPACE_STR "@std@@3V?$basic_istream at DU?$char_traits at D@" _LIBCPP_ABI_NAMESPACE_STR
-            "@std@@@12 at A")
-#endif
-        ;
-alignas(__stdinbuf<char>) static char __cin[sizeof(__stdinbuf<char>)];
 static mbstate_t mb_cin;
+static mbstate_t mb_cout;
+static mbstate_t mb_cerr;
 
 #if _LIBCPP_HAS_WIDE_CHARACTERS
-alignas(wistream) _LIBCPP_EXPORTED_FROM_ABI char wcin[sizeof(wistream)]
-#  if defined(_LIBCPP_ABI_MICROSOFT) && defined(__clang__)
-    __asm__("?wcin@" _LIBCPP_ABI_NAMESPACE_STR "@std@@3V?$basic_istream at _WU?$char_traits at _W@" _LIBCPP_ABI_NAMESPACE_STR
-            "@std@@@12 at A")
-#  endif
-        ;
-alignas(__stdinbuf<wchar_t>) static char __wcin[sizeof(__stdinbuf<wchar_t>)];
 static mbstate_t mb_wcin;
-#endif // _LIBCPP_HAS_WIDE_CHARACTERS
-
-alignas(ostream) _LIBCPP_EXPORTED_FROM_ABI char cout[sizeof(ostream)]
-#if defined(_LIBCPP_ABI_MICROSOFT) && defined(__clang__)
-    __asm__("?cout@" _LIBCPP_ABI_NAMESPACE_STR "@std@@3V?$basic_ostream at DU?$char_traits at D@" _LIBCPP_ABI_NAMESPACE_STR
-            "@std@@@12 at A")
+static mbstate_t mb_wcout;
+static mbstate_t mb_wcerr;
 #endif
-        ;
-alignas(__stdoutbuf<char>) static char __cout[sizeof(__stdoutbuf<char>)];
-static mbstate_t mb_cout;
 
-#if _LIBCPP_HAS_WIDE_CHARACTERS
-alignas(wostream) _LIBCPP_EXPORTED_FROM_ABI char wcout[sizeof(wostream)]
-#  if defined(_LIBCPP_ABI_MICROSOFT) && defined(__clang__)
-    __asm__("?wcout@" _LIBCPP_ABI_NAMESPACE_STR "@std@@3V?$basic_ostream at _WU?$char_traits at _W@" _LIBCPP_ABI_NAMESPACE_STR
-            "@std@@@12 at A")
-#  endif
-        ;
-alignas(__stdoutbuf<wchar_t>) static char __wcout[sizeof(__stdoutbuf<wchar_t>)];
-static mbstate_t mb_wcout;
-#endif // _LIBCPP_HAS_WIDE_CHARACTERS
+#if __has_cpp_attribute(clang::no_destroy)
+template <class T>
+using no_destroy_t = T;
 
-alignas(ostream) _LIBCPP_EXPORTED_FROM_ABI char cerr[sizeof(ostream)]
-#if defined(_LIBCPP_ABI_MICROSOFT) && defined(__clang__)
-    __asm__("?cerr@" _LIBCPP_ABI_NAMESPACE_STR "@std@@3V?$basic_ostream at DU?$char_traits at D@" _LIBCPP_ABI_NAMESPACE_STR
-            "@std@@@12 at A")
+#  define STREAM_ATTRS [[clang::no_destroy]] _LIBCPP_INIT_PRIORITY_MAX
+#else
+template <class T>
+using no_destroy_t = __no_destroy<T>;
+
+#  define STREAM_ATTRS _LIBCPP_INIT_PRIORITY_MAX
 #endif
-        ;
-alignas(__stdoutbuf<char>) static char __cerr[sizeof(__stdoutbuf<char>)];
-static mbstate_t mb_cerr;
 
-#if _LIBCPP_HAS_WIDE_CHARACTERS
-alignas(wostream) _LIBCPP_EXPORTED_FROM_ABI char wcerr[sizeof(wostream)]
-#  if defined(_LIBCPP_ABI_MICROSOFT) && defined(__clang__)
-    __asm__("?wcerr@" _LIBCPP_ABI_NAMESPACE_STR "@std@@3V?$basic_ostream at _WU?$char_traits at _W@" _LIBCPP_ABI_NAMESPACE_STR
-            "@std@@@12 at A")
-#  endif
-        ;
-alignas(__stdoutbuf<wchar_t>) static char __wcerr[sizeof(__stdoutbuf<wchar_t>)];
-static mbstate_t mb_wcerr;
-#endif // _LIBCPP_HAS_WIDE_CHARACTERS
+auto&& unwrap(auto& val) { return val; }
----------------
ldionne wrote:

```suggestion
inline auto&& unwrap(auto& val) { return val; }
```

If you decide to write this as an auto function, let's make the linkage clear by using `inline`.

https://github.com/llvm/llvm-project/pull/121116