Make the presence of stdin and stdout optional.

The idea behind Nuxi CloudABI is that it is targeted at (but not limited to)
running networked services in a sandboxed environment. The model behind stdin,
stdout and stderr is strongly focused on interactive tools in a command shell.
CloudABI does not support the notion of stdin and stdout, as 'standard
input/output' does not apply to services. The concept of stderr does makes
sense though, as services do need some mechanism to log error messages in a
uniform way.

This patch extends libc++ in such a way that std::cin and std::cout and the
associated <cstdio>/<cwchar> functions can be disabled through the flags
_LIBCPP_HAS_NO_STDIN and _LIBCPP_HAS_NO_STDOUT, respectively. At the same time
it attempts to clean up src/iostream.cpp a bit. Instead of using a single array
of mbstate_t objects and hardcoding the array indices, it creates separate
objects that declared next to the iostream objects and their buffers. The code
is also restructured by interleaving the construction and setup of c* and wc*
objects. That way it is more obvious that this is done identically.

The c* and wc* objects already have separate unit tests. Make use of this fact
by adding XFAILs in case libcpp-has-no-std* is set. That way the tests work in
both directions. If stdin or stdout is disabled, these tests will therefore
test for the absence of c* and wc*.

Differential Revision:	http://reviews.llvm.org/D8340

llvm-svn: 233275

1 files changed, 14 insertions, 0 deletions

diff --git a/libcxx/src/iostream.cpp b/libcxx/src/iostream.cpp
index e404535a36f..e073aec6ead 100644
--- a/libcxx/src/iostream.cpp
+++ b/libcxx/src/iostream.cpp
@@ -13,19 +13,23 @@
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
+#ifndef _LIBCPP_HAS_NO_STDIN
 _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;
+#endif
 
+#ifndef _LIBCPP_HAS_NO_STDOUT
 _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;
+#endif
 
 _ALIGNAS_TYPE (ostream)  _LIBCPP_FUNC_VIS char cerr[sizeof(ostream)];
 _ALIGNAS_TYPE (__stdoutbuf<char>) static char __cerr[sizeof(__stdoutbuf<char>)];
@@ -41,29 +45,39 @@ ios_base::Init __start_std_streams;
 
 ios_base::Init::Init()
 {
+#ifndef _LIBCPP_HAS_NO_STDIN
     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));
+#endif
+#ifndef _LIBCPP_HAS_NO_STDOUT
     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));
+#endif
     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, &mb_wcerr));
                           ::new(wclog) wostream(wcerr_ptr->rdbuf());
 
+#if !defined(_LIBCPP_HAS_NO_STDIN) && !defined(_LIBCPP_HAS_NO_STDOUT)
     cin_ptr->tie(cout_ptr);
     wcin_ptr->tie(wcout_ptr);
+#endif
     _VSTD::unitbuf(*cerr_ptr);
     _VSTD::unitbuf(*wcerr_ptr);
+#ifndef _LIBCPP_HAS_NO_STDOUT
     cerr_ptr->tie(cout_ptr);
     wcerr_ptr->tie(wcout_ptr);
+#endif
 }
 
 ios_base::Init::~Init()
 {
+#ifndef _LIBCPP_HAS_NO_STDOUT
     ostream* cout_ptr = reinterpret_cast<ostream*>(cout);
     wostream* wcout_ptr = reinterpret_cast<wostream*>(wcout);
     cout_ptr->flush();
     wcout_ptr->flush();
+#endif
 
     ostream* clog_ptr = reinterpret_cast<ostream*>(clog);
     wostream* wclog_ptr = reinterpret_cast<wostream*>(wclog);