[libc++] Split off iostreams explicit instantiations into its own source file

This makes it cleaner to add more instantiations without cluttering the
actual implementation of ios.

Author: ldionne

libcxx/src/CMakeLists.txt

@@ -64,6 +64,7 @@ endif()
 if (LIBCXX_ENABLE_LOCALIZATION)
   list(APPEND LIBCXX_SOURCES
     ios.cpp
+    ios.instantiations.cpp
     iostream.cpp
     locale.cpp
     regex.cpp

libcxx/src/ios.cpp

@@ -15,30 +15,14 @@
 #include "__locale"
 #include "algorithm"
 #include "include/config_elast.h"
-#include "istream"
 #include "limits"
 #include "memory"
 #include "new"
-#include "streambuf"
 #include "string"
 #include "__undef_macros"
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-template class _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS basic_ios<char>;
-template class _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS basic_ios<wchar_t>;
-
-template class _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS basic_streambuf<char>;
-template class _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS basic_streambuf<wchar_t>;
-
-template class _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS basic_istream<char>;
-template class _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS basic_istream<wchar_t>;
-
-template class _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS basic_ostream<char>;
-template class _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS basic_ostream<wchar_t>;
-
-template class _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS basic_iostream<char>;
-
 class _LIBCPP_HIDDEN __iostream_category
     : public __do_message
 {

libcxx/src/ios.instantiations.cpp

@@ -0,0 +1,31 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "__config"
+#include "ios"
+#include "istream"
+#include "ostream"
+#include "streambuf"
+
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+// Original explicit instantiations provided in the library
+template class _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS basic_ios<char>;
+template class _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS basic_ios<wchar_t>;
+template class _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS basic_streambuf<char>;
+template class _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS basic_streambuf<wchar_t>;
+template class _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS basic_istream<char>;
+template class _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS basic_istream<wchar_t>;
+template class _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS basic_ostream<char>;
+template class _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS basic_ostream<wchar_t>;
+template class _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS basic_iostream<char>;
+
+// Add more here if needed...
+
+_LIBCPP_END_NAMESPACE_STD