Remove the state_types array

[ed]

Summary

If we want to add support for making std::cin and std::cout optional, it is impractical to have all of the mbstate_t objects in one array. This would mean that if std::cin and std::cout are omitted, the state_types array is only used partially.

Solve this by using separate global variables. These are placed right next to the iostream object and the buffer, meaning we can easily #ifdef them away.

[jroelofs]

Hi @ed,

This looks fine, but as a reminder of the developer policy: http://llvm.org/docs/DeveloperPolicy.html#id11 the right thing to do is to ping your patches weekly until you get feedback or a "LGTM", rather than committing them after the review has gone stagnant. Pinging helps remind us about the reviews... sorry I forgot about yours.

Cheers,

Jon

[ed]

In D8359#147290, @jroelofs wrote:

This looks fine, but as a reminder of the developer policy: http://llvm.org/docs/DeveloperPolicy.html#id11 the right thing to do is to ping your patches weekly until you get feedback or a "LGTM", rather than committing them after the review has gone stagnant. Pinging helps remind us about the reviews... sorry I forgot about yours.

And sorry from my side for being a bit impatient. I should have pinged. :-)

libcxx/trunk/src/iostream.cpp

 //===------------------------ iostream.cpp --------------------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is dual licensed under the MIT and the University of Illinois Open
 // Source Licenses. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 
 #include "__std_stream"
 #include "string"
 #include "new"
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-static mbstate_t state_types[6] = {};
-
 _ALIGNAS_TYPE (istream)  _LIBCPP_FUNC_VIS char cin [sizeof(istream)];
 _ALIGNAS_TYPE (__stdinbuf<char> ) static char __cin [sizeof(__stdinbuf <char>)];
+static mbstate_t mb_cin;
 _ALIGNAS_TYPE (wistream) _LIBCPP_FUNC_VIS char wcin [sizeof(wistream)];
 _ALIGNAS_TYPE (__stdinbuf<wchar_t> ) static char __wcin [sizeof(__stdinbuf <wchar_t>)];
+static mbstate_t mb_wcin;
 
 _ALIGNAS_TYPE (ostream)  _LIBCPP_FUNC_VIS char cout[sizeof(ostream)];
 _ALIGNAS_TYPE (__stdoutbuf<char>) static char __cout[sizeof(__stdoutbuf<char>)];
+static mbstate_t mb_cout;
 _ALIGNAS_TYPE (wostream) _LIBCPP_FUNC_VIS char wcout[sizeof(wostream)];
 _ALIGNAS_TYPE (__stdoutbuf<wchar_t>) static char __wcout[sizeof(__stdoutbuf<wchar_t>)];
+static mbstate_t mb_wcout;
 
 _ALIGNAS_TYPE (ostream)  _LIBCPP_FUNC_VIS char cerr[sizeof(ostream)];
 _ALIGNAS_TYPE (__stdoutbuf<char>) static char __cerr[sizeof(__stdoutbuf<char>)];
+static mbstate_t mb_cerr;
 _ALIGNAS_TYPE (wostream) _LIBCPP_FUNC_VIS char wcerr[sizeof(wostream)];
 _ALIGNAS_TYPE (__stdoutbuf<wchar_t>) static char __wcerr[sizeof(__stdoutbuf<wchar_t>)];
+static mbstate_t mb_wcerr;
 
 _ALIGNAS_TYPE (ostream)  _LIBCPP_FUNC_VIS char clog[sizeof(ostream)];
 _ALIGNAS_TYPE (wostream) _LIBCPP_FUNC_VIS char wclog[sizeof(wostream)];
 
 ios_base::Init __start_std_streams;
 
 ios_base::Init::Init()
 {
-    istream* cin_ptr  = ::new(cin)  istream(::new(__cin)  __stdinbuf <char>(stdin, state_types+0) );
-    wistream* wcin_ptr  = ::new(wcin)  wistream(::new(__wcin)  __stdinbuf <wchar_t>(stdin, state_types+3) );
-    ostream* cout_ptr = ::new(cout) ostream(::new(__cout) __stdoutbuf<char>(stdout, state_types+1));
-    wostream* wcout_ptr = ::new(wcout) wostream(::new(__wcout) __stdoutbuf<wchar_t>(stdout, state_types+4));
-    ostream* cerr_ptr = ::new(cerr) ostream(::new(__cerr) __stdoutbuf<char>(stderr, state_types+2));
+    istream* cin_ptr  = ::new(cin)  istream(::new(__cin)  __stdinbuf <char>(stdin, &mb_cin));
+    wistream* wcin_ptr  = ::new(wcin)  wistream(::new(__wcin)  __stdinbuf <wchar_t>(stdin, &mb_wcin));
+    ostream* cout_ptr = ::new(cout) ostream(::new(__cout) __stdoutbuf<char>(stdout, &mb_cout));
+    wostream* wcout_ptr = ::new(wcout) wostream(::new(__wcout) __stdoutbuf<wchar_t>(stdout, &mb_wcout));
+    ostream* cerr_ptr = ::new(cerr) ostream(::new(__cerr) __stdoutbuf<char>(stderr, &mb_cerr));
                         ::new(clog) ostream(cerr_ptr->rdbuf());
-    wostream* wcerr_ptr = ::new(wcerr) wostream(::new(__wcerr) __stdoutbuf<wchar_t>(stderr, state_types+5));
+    wostream* wcerr_ptr = ::new(wcerr) wostream(::new(__wcerr) __stdoutbuf<wchar_t>(stderr, &mb_wcerr));
                           ::new(wclog) wostream(wcerr_ptr->rdbuf());
 
     cin_ptr->tie(cout_ptr);
     wcin_ptr->tie(wcout_ptr);
     _VSTD::unitbuf(*cerr_ptr);
     _VSTD::unitbuf(*wcerr_ptr);
     cerr_ptr->tie(cout_ptr);
     wcerr_ptr->tie(wcout_ptr);