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

17 files changed, 158 insertions, 55 deletions

diff --git a/libcxx/CMakeLists.txt b/libcxx/CMakeLists.txt
index 07373572317..82a35e0c6b6 100644
--- a/libcxx/CMakeLists.txt
+++ b/libcxx/CMakeLists.txt
@@ -55,6 +55,8 @@ option(LIBCXX_ENABLE_WERROR "Fail and stop if a warning is triggered." OFF)
 option(LIBCXX_ENABLE_CXX1Y "Enable -std=c++1y and use of c++1y language features if the compiler supports it." OFF)
 option(LIBCXX_ENABLE_SHARED "Build libc++ as a shared library." ON)
 option(LIBCXX_ENABLE_GLOBAL_FILESYSTEM_NAMESPACE "Build libc++ with support for the global filesystem namespace." ON)
+option(LIBCXX_ENABLE_STDIN "Build libc++ with support for stdin/std::cin." ON)
+option(LIBCXX_ENABLE_STDOUT "Build libc++ with support for stdout/std::cout." ON)
 option(LIBCXX_ENABLE_THREADS "Build libc++ with support for threads." ON)
 option(LIBCXX_BUILD_32_BITS "Build 32 bit libc++" OFF)
 option(LIBCXX_ENABLE_MONOTONIC_CLOCK
@@ -259,6 +261,16 @@ if (NOT LIBCXX_ENABLE_GLOBAL_FILESYSTEM_NAMESPACE)
   add_definitions(-D_LIBCPP_HAS_NO_GLOBAL_FILESYSTEM_NAMESPACE)
 endif()
 
+# LIBCXX_ENABLE_STDIN configuration
+if (NOT LIBCXX_ENABLE_STDIN)
+  add_definitions(-D_LIBCPP_HAS_NO_STDIN)
+endif()
+
+# LIBCXX_ENABLE_STDOUT configuration
+if (NOT LIBCXX_ENABLE_STDOUT)
+  add_definitions(-D_LIBCPP_HAS_NO_STDOUT)
+endif()
+
 # LIBCXX_ENABLE_THREADS configuration
 if (NOT LIBCXX_ENABLE_THREADS)
   add_definitions(-D_LIBCPP_HAS_NO_THREADS)
diff --git a/libcxx/include/__config b/libcxx/include/__config
index 33c386b18dc..97c66c85e38 100644
--- a/libcxx/include/__config
+++ b/libcxx/include/__config
@@ -740,6 +740,13 @@ extern "C" void __sanitizer_annotate_contiguous_container(
 #define _LIBCPP_HAS_NO_GLOBAL_FILESYSTEM_NAMESPACE
 #endif
 
+// CloudABI is intended for running networked services. Processes do not
+// have standard input and output channels.
+#ifdef __CloudABI__
+#define _LIBCPP_HAS_NO_STDIN
+#define _LIBCPP_HAS_NO_STDOUT
+#endif
+
 #if defined(__ANDROID__) || defined(__CloudABI__)
 #define _LIBCPP_PROVIDES_DEFAULT_RUNE_TABLE
 #endif
diff --git a/libcxx/include/cstdio b/libcxx/include/cstdio
index 8c4e627fc74..d8ba6c2ef38 100644
--- a/libcxx/include/cstdio
+++ b/libcxx/include/cstdio
@@ -144,34 +144,20 @@ using ::FILE;
 using ::fpos_t;
 using ::size_t;
 
-#ifndef _LIBCPP_HAS_NO_GLOBAL_FILESYSTEM_NAMESPACE
-using ::remove;
-using ::rename;
-using ::tmpfile;
-using ::tmpnam;
-#endif
 using ::fclose;
 using ::fflush;
-#ifndef _LIBCPP_HAS_NO_GLOBAL_FILESYSTEM_NAMESPACE
-using ::fopen;
-using ::freopen;
-#endif
 using ::setbuf;
 using ::setvbuf;
 using ::fprintf;
 using ::fscanf;
-using ::printf;
-using ::scanf;
 using ::snprintf;
 using ::sprintf;
 using ::sscanf;
 #ifndef _LIBCPP_MSVCRT
 using ::vfprintf;
 using ::vfscanf;
-using ::vscanf;
 using ::vsscanf;
 #endif // _LIBCPP_MSVCRT
-using ::vprintf;
 using ::vsnprintf;
 using ::vsprintf;
 using ::fgetc;
@@ -179,13 +165,7 @@ using ::fgets;
 using ::fputc;
 using ::fputs;
 using ::getc;
-using ::getchar;
-#if _LIBCPP_STD_VER <= 11
-using ::gets;
-#endif
 using ::putc;
-using ::putchar;
-using ::puts;
 using ::ungetc;
 using ::fread;
 using ::fwrite;
@@ -199,6 +179,31 @@ using ::feof;
 using ::ferror;
 using ::perror;
 
+#ifndef _LIBCPP_HAS_NO_GLOBAL_FILESYSTEM_NAMESPACE
+using ::fopen;
+using ::freopen;
+using ::remove;
+using ::rename;
+using ::tmpfile;
+using ::tmpnam;
+#endif
+
+#ifndef _LIBCPP_HAS_NO_STDIN
+using ::getchar;
+#if _LIBCPP_STD_VER <= 11
+using ::gets;
+#endif
+using ::scanf;
+using ::vscanf;
+#endif
+
+#ifndef _LIBCPP_HAS_NO_STDOUT
+using ::printf;
+using ::putchar;
+using ::puts;
+using ::vprintf;
+#endif
+
 _LIBCPP_END_NAMESPACE_STD
 
 #endif  // _LIBCPP_CSTDIO
diff --git a/libcxx/include/cwchar b/libcxx/include/cwchar
index 9f51587caa5..797a1777c22 100644
--- a/libcxx/include/cwchar
+++ b/libcxx/include/cwchar
@@ -126,24 +126,18 @@ using ::fwscanf;
 using ::swprintf;
 using ::vfwprintf;
 using ::vswprintf;
-using ::vwprintf;
 #ifndef _LIBCPP_MSVCRT
 using ::swscanf;
 using ::vfwscanf;
 using ::vswscanf;
-using ::vwscanf;
 #endif // _LIBCPP_MSVCRT
-using ::wprintf;
-using ::wscanf;
 using ::fgetwc;
 using ::fgetws;
 using ::fputwc;
 using ::fputws;
 using ::fwide;
 using ::getwc;
-using ::getwchar;
 using ::putwc;
-using ::putwchar;
 using ::ungetwc;
 using ::wcstod;
 #ifndef _LIBCPP_MSVCRT
@@ -212,6 +206,20 @@ using ::wcrtomb;
 using ::mbsrtowcs;
 using ::wcsrtombs;
 
+#ifndef _LIBCPP_HAS_NO_STDIN
+using ::getwchar;
+#ifndef _LIBCPP_MSVCRT
+using ::vwscanf;
+#endif // _LIBCPP_MSVCRT
+using ::wscanf;
+#endif
+
+#ifndef _LIBCPP_HAS_NO_STDOUT
+using ::putwchar;
+using ::vwprintf;
+using ::wprintf;
+#endif
+
 _LIBCPP_END_NAMESPACE_STD
 
 #endif  // _LIBCPP_CWCHAR
diff --git a/libcxx/include/iostream b/libcxx/include/iostream
index ddf24841144..136a849777f 100644
--- a/libcxx/include/iostream
+++ b/libcxx/include/iostream
@@ -46,13 +46,17 @@ extern wostream wclog;
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
+#ifndef _LIBCPP_HAS_NO_STDIN
 extern _LIBCPP_FUNC_VIS istream cin;
-extern _LIBCPP_FUNC_VIS ostream cout;
-extern _LIBCPP_FUNC_VIS ostream cerr;
-extern _LIBCPP_FUNC_VIS ostream clog;
 extern _LIBCPP_FUNC_VIS wistream wcin;
+#endif
+#ifndef _LIBCPP_HAS_NO_STDOUT
+extern _LIBCPP_FUNC_VIS ostream cout;
 extern _LIBCPP_FUNC_VIS wostream wcout;
+#endif
+extern _LIBCPP_FUNC_VIS ostream cerr;
 extern _LIBCPP_FUNC_VIS wostream wcerr;
+extern _LIBCPP_FUNC_VIS ostream clog;
 extern _LIBCPP_FUNC_VIS wostream wclog;
 
 _LIBCPP_END_NAMESPACE_STD
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);
diff --git a/libcxx/test/CMakeLists.txt b/libcxx/test/CMakeLists.txt
index cb78fcf231e..707acd1d479 100644
--- a/libcxx/test/CMakeLists.txt
+++ b/libcxx/test/CMakeLists.txt
@@ -43,6 +43,8 @@ if (LIT_EXECUTABLE)
   pythonize_bool(LIBCXX_ENABLE_SHARED)
   pythonize_bool(LIBCXX_BUILD_32_BITS)
   pythonize_bool(LIBCXX_ENABLE_GLOBAL_FILESYSTEM_NAMESPACE)
+  pythonize_bool(LIBCXX_ENABLE_STDIN)
+  pythonize_bool(LIBCXX_ENABLE_STDOUT)
   pythonize_bool(LIBCXX_ENABLE_THREADS)
   pythonize_bool(LIBCXX_ENABLE_MONOTONIC_CLOCK)
   # The tests shouldn't link to any ABI library when it has been linked into
diff --git a/libcxx/test/libcxx/test/config.py b/libcxx/test/libcxx/test/config.py
index 71cc9f014fb..b86a1ef4edf 100644
--- a/libcxx/test/libcxx/test/config.py
+++ b/libcxx/test/libcxx/test/config.py
@@ -349,6 +349,8 @@ class Configuration(object):
         self.configure_compile_flags_exceptions()
         self.configure_compile_flags_rtti()
         self.configure_compile_flags_no_global_filesystem_namespace()
+        self.configure_compile_flags_no_stdin()
+        self.configure_compile_flags_no_stdout()
         enable_32bit = self.get_lit_bool('enable_32bit', False)
         if enable_32bit:
             self.cxx.flags += ['-m32']
@@ -406,6 +408,18 @@ class Configuration(object):
             self.cxx.compile_flags += [
                 '-D_LIBCPP_HAS_NO_GLOBAL_FILESYSTEM_NAMESPACE']
 
+    def configure_compile_flags_no_stdin(self):
+        enable_stdin = self.get_lit_bool('enable_stdin', True)
+        if not enable_stdin:
+            self.config.available_features.add('libcpp-has-no-stdin')
+            self.cxx.compile_flags += ['-D_LIBCPP_HAS_NO_STDIN']
+
+    def configure_compile_flags_no_stdout(self):
+        enable_stdout = self.get_lit_bool('enable_stdout', True)
+        if not enable_stdout:
+            self.config.available_features.add('libcpp-has-no-stdout')
+            self.cxx.compile_flags += ['-D_LIBCPP_HAS_NO_STDOUT']
+
     def configure_compile_flags_no_threads(self):
         self.cxx.compile_flags += ['-D_LIBCPP_HAS_NO_THREADS']
         self.config.available_features.add('libcpp-has-no-threads')
diff --git a/libcxx/test/lit.site.cfg.in b/libcxx/test/lit.site.cfg.in
index db79581fd24..31eb73be0eb 100644
--- a/libcxx/test/lit.site.cfg.in
+++ b/libcxx/test/lit.site.cfg.in
@@ -9,6 +9,8 @@ config.enable_rtti              = "@LIBCXX_ENABLE_RTTI@"
 config.enable_shared            = "@LIBCXX_ENABLE_SHARED@"
 config.enable_32bit             = "@LIBCXX_BUILD_32_BITS@"
 config.enable_global_filesystem_namespace = "@LIBCXX_ENABLE_GLOBAL_FILESYSTEM_NAMESPACE@"
+config.enable_stdin             = "@LIBCXX_ENABLE_STDIN@"
+config.enable_stdout            = "@LIBCXX_ENABLE_STDOUT@"
 config.enable_threads           = "@LIBCXX_ENABLE_THREADS@"
 config.enable_monotonic_clock   = "@LIBCXX_ENABLE_MONOTONIC_CLOCK@"
 config.cxx_abi                  = "@LIBCXX_CXX_ABI_LIBNAME@"
diff --git a/libcxx/test/std/input.output/file.streams/c.files/cstdio.pass.cpp b/libcxx/test/std/input.output/file.streams/c.files/cstdio.pass.cpp
index 2ea09bc7bec..ec4ad8a3bbc 100644
--- a/libcxx/test/std/input.output/file.streams/c.files/cstdio.pass.cpp
+++ b/libcxx/test/std/input.output/file.streams/c.files/cstdio.pass.cpp
@@ -88,31 +88,17 @@ int main()
     std::size_t s = 0;
     char* cp = 0;
     std::va_list va;
-#ifndef _LIBCPP_HAS_NO_GLOBAL_FILESYSTEM_NAMESPACE
-    static_assert((std::is_same<decltype(std::remove("")), int>::value), "");
-    static_assert((std::is_same<decltype(std::rename("","")), int>::value), "");
-    static_assert((std::is_same<decltype(std::tmpfile()), std::FILE*>::value), "");
-    static_assert((std::is_same<decltype(std::tmpnam(cp)), char*>::value), "");
-#endif
     static_assert((std::is_same<decltype(std::fclose(fp)), int>::value), "");
     static_assert((std::is_same<decltype(std::fflush(fp)), int>::value), "");
-#ifndef _LIBCPP_HAS_NO_GLOBAL_FILESYSTEM_NAMESPACE
-    static_assert((std::is_same<decltype(std::fopen("", "")), std::FILE*>::value), "");
-    static_assert((std::is_same<decltype(std::freopen("", "", fp)), std::FILE*>::value), "");
-#endif
     static_assert((std::is_same<decltype(std::setbuf(fp,cp)), void>::value), "");
     static_assert((std::is_same<decltype(std::vfprintf(fp,"",va)), int>::value), "");
     static_assert((std::is_same<decltype(std::fprintf(fp," ")), int>::value), "");
     static_assert((std::is_same<decltype(std::fscanf(fp,"")), int>::value), "");
-    static_assert((std::is_same<decltype(std::printf(" ")), int>::value), "");
-    static_assert((std::is_same<decltype(std::scanf(" ")), int>::value), "");
     static_assert((std::is_same<decltype(std::snprintf(cp,0," ")), int>::value), "");
     static_assert((std::is_same<decltype(std::sprintf(cp," ")), int>::value), "");
     static_assert((std::is_same<decltype(std::sscanf("","")), int>::value), "");
     static_assert((std::is_same<decltype(std::vfprintf(fp,"",va)), int>::value), "");
     static_assert((std::is_same<decltype(std::vfscanf(fp,"",va)), int>::value), "");
-    static_assert((std::is_same<decltype(std::vprintf(" ",va)), int>::value), "");
-    static_assert((std::is_same<decltype(std::vscanf("",va)), int>::value), "");
     static_assert((std::is_same<decltype(std::vsnprintf(cp,0," ",va)), int>::value), "");
     static_assert((std::is_same<decltype(std::vsprintf(cp," ",va)), int>::value), "");
     static_assert((std::is_same<decltype(std::vsscanf("","",va)), int>::value), "");
@@ -121,13 +107,7 @@ int main()
     static_assert((std::is_same<decltype(std::fputc(0,fp)), int>::value), "");
     static_assert((std::is_same<decltype(std::fputs("",fp)), int>::value), "");
     static_assert((std::is_same<decltype(std::getc(fp)), int>::value), "");
-    static_assert((std::is_same<decltype(std::getchar()), int>::value), "");
-#if _LIBCPP_STD_VER <= 11
-    static_assert((std::is_same<decltype(std::gets(cp)), char*>::value), "");
-#endif
     static_assert((std::is_same<decltype(std::putc(0,fp)), int>::value), "");
-    static_assert((std::is_same<decltype(std::putchar(0)), int>::value), "");
-    static_assert((std::is_same<decltype(std::puts("")), int>::value), "");
     static_assert((std::is_same<decltype(std::ungetc(0,fp)), int>::value), "");
     static_assert((std::is_same<decltype(std::fread((void*)0,0,0,fp)), std::size_t>::value), "");
     static_assert((std::is_same<decltype(std::fwrite((const void*)0,0,0,fp)), std::size_t>::value), "");
@@ -140,4 +120,29 @@ int main()
     static_assert((std::is_same<decltype(std::feof(fp)), int>::value), "");
     static_assert((std::is_same<decltype(std::ferror(fp)), int>::value), "");
     static_assert((std::is_same<decltype(std::perror("")), void>::value), "");
+
+#ifndef _LIBCPP_HAS_NO_GLOBAL_FILESYSTEM_NAMESPACE
+    static_assert((std::is_same<decltype(std::fopen("", "")), std::FILE*>::value), "");
+    static_assert((std::is_same<decltype(std::freopen("", "", fp)), std::FILE*>::value), "");
+    static_assert((std::is_same<decltype(std::remove("")), int>::value), "");
+    static_assert((std::is_same<decltype(std::rename("","")), int>::value), "");
+    static_assert((std::is_same<decltype(std::tmpfile()), std::FILE*>::value), "");
+    static_assert((std::is_same<decltype(std::tmpnam(cp)), char*>::value), "");
+#endif
+
+#ifndef _LIBCPP_HAS_NO_STDIN
+    static_assert((std::is_same<decltype(std::getchar()), int>::value), "");
+#if _LIBCPP_STD_VER <= 11
+    static_assert((std::is_same<decltype(std::gets(cp)), char*>::value), "");
+#endif
+    static_assert((std::is_same<decltype(std::scanf(" ")), int>::value), "");
+    static_assert((std::is_same<decltype(std::vscanf("",va)), int>::value), "");
+#endif
+
+#ifndef _LIBCPP_HAS_NO_STDOUT
+    static_assert((std::is_same<decltype(std::printf(" ")), int>::value), "");
+    static_assert((std::is_same<decltype(std::putchar(0)), int>::value), "");
+    static_assert((std::is_same<decltype(std::puts("")), int>::value), "");
+    static_assert((std::is_same<decltype(std::vprintf(" ",va)), int>::value), "");
+#endif
 }
diff --git a/libcxx/test/std/input.output/iostream.objects/narrow.stream.objects/cerr.pass.cpp b/libcxx/test/std/input.output/iostream.objects/narrow.stream.objects/cerr.pass.cpp
index 9206d173fc0..cdf53f86277 100644
--- a/libcxx/test/std/input.output/iostream.objects/narrow.stream.objects/cerr.pass.cpp
+++ b/libcxx/test/std/input.output/iostream.objects/narrow.stream.objects/cerr.pass.cpp
@@ -19,7 +19,11 @@ int main()
 #if 0
     std::cerr << "Hello World!\n";
 #else
+#ifdef _LIBCPP_HAS_NO_STDOUT
+    assert(std::cerr.tie() == NULL);
+#else
     assert(std::cerr.tie() == &std::cout);
+#endif
     assert(std::cerr.flags() & std::ios_base::unitbuf);
 #endif  // 0
 }
diff --git a/libcxx/test/std/input.output/iostream.objects/narrow.stream.objects/cin.pass.cpp b/libcxx/test/std/input.output/iostream.objects/narrow.stream.objects/cin.pass.cpp
index 3481598aed9..1ce04ffb156 100644
--- a/libcxx/test/std/input.output/iostream.objects/narrow.stream.objects/cin.pass.cpp
+++ b/libcxx/test/std/input.output/iostream.objects/narrow.stream.objects/cin.pass.cpp
@@ -7,6 +7,8 @@
 //
 //===----------------------------------------------------------------------===//
 
+// XFAIL: libcpp-has-no-stdin
+
 // <iostream>
 
 // istream cin;
@@ -23,6 +25,10 @@ int main()
     std::cin >> i;
     std::cout << "The number is : " << i << '\n';
 #else  // 0
+#ifdef _LIBCPP_HAS_NO_STDOUT
+    assert(std::cin.tie() == NULL);
+#else
     assert(std::cin.tie() == &std::cout);
 #endif
+#endif
 }
diff --git a/libcxx/test/std/input.output/iostream.objects/narrow.stream.objects/cout.pass.cpp b/libcxx/test/std/input.output/iostream.objects/narrow.stream.objects/cout.pass.cpp
index 6000ae274b9..e5887e1625d 100644
--- a/libcxx/test/std/input.output/iostream.objects/narrow.stream.objects/cout.pass.cpp
+++ b/libcxx/test/std/input.output/iostream.objects/narrow.stream.objects/cout.pass.cpp
@@ -7,6 +7,8 @@
 //
 //===----------------------------------------------------------------------===//
 
+// XFAIL: libcpp-has-no-stdout
+
 // <iostream>
 
 // istream cout;
diff --git a/libcxx/test/std/input.output/iostream.objects/wide.stream.objects/wcerr.pass.cpp b/libcxx/test/std/input.output/iostream.objects/wide.stream.objects/wcerr.pass.cpp
index 19a1dcdcdb4..b050781671e 100644
--- a/libcxx/test/std/input.output/iostream.objects/wide.stream.objects/wcerr.pass.cpp
+++ b/libcxx/test/std/input.output/iostream.objects/wide.stream.objects/wcerr.pass.cpp
@@ -19,7 +19,11 @@ int main()
 #if 0
     std::wcerr << L"Hello World!\n";
 #else
+#ifdef _LIBCPP_HAS_NO_STDOUT
+    assert(std::wcerr.tie() == NULL);
+#else
     assert(std::wcerr.tie() == &std::wcout);
+#endif
     assert(std::wcerr.flags() & std::ios_base::unitbuf);
 #endif  // 0
 }
diff --git a/libcxx/test/std/input.output/iostream.objects/wide.stream.objects/wcin.pass.cpp b/libcxx/test/std/input.output/iostream.objects/wide.stream.objects/wcin.pass.cpp
index 90a56685a67..6abd6afa81c 100644
--- a/libcxx/test/std/input.output/iostream.objects/wide.stream.objects/wcin.pass.cpp
+++ b/libcxx/test/std/input.output/iostream.objects/wide.stream.objects/wcin.pass.cpp
@@ -7,6 +7,8 @@
 //
 //===----------------------------------------------------------------------===//
 
+// XFAIL: libcpp-has-no-stdin
+
 // <iostream>
 
 // istream wcin;
@@ -23,6 +25,10 @@ int main()
     std::wcin >> i;
     std::wcout << L"The number is : " << i << L'\n';
 #else  // 0
+#ifdef _LIBCPP_HAS_NO_STDOUT
+    assert(std::wcin.tie() == NULL);
+#else
     assert(std::wcin.tie() == &std::wcout);
 #endif
+#endif
 }
diff --git a/libcxx/test/std/input.output/iostream.objects/wide.stream.objects/wcout.pass.cpp b/libcxx/test/std/input.output/iostream.objects/wide.stream.objects/wcout.pass.cpp
index 7a546aa528d..6543e0aa56a 100644
--- a/libcxx/test/std/input.output/iostream.objects/wide.stream.objects/wcout.pass.cpp
+++ b/libcxx/test/std/input.output/iostream.objects/wide.stream.objects/wcout.pass.cpp
@@ -7,6 +7,8 @@
 //
 //===----------------------------------------------------------------------===//
 
+// XFAIL: libcpp-has-no-stdout
+
 // <iostream>
 
 // istream wcout;
diff --git a/libcxx/test/std/strings/c.strings/cwchar.pass.cpp b/libcxx/test/std/strings/c.strings/cwchar.pass.cpp
index d0481b70610..c3d868fbc3b 100644
--- a/libcxx/test/std/strings/c.strings/cwchar.pass.cpp
+++ b/libcxx/test/std/strings/c.strings/cwchar.pass.cpp
@@ -50,19 +50,13 @@ int main()
     static_assert((std::is_same<decltype(std::vfwscanf(fp, L"", va)), int>::value), "");
     static_assert((std::is_same<decltype(std::vswprintf(ws, s, L"", va)), int>::value), "");
     static_assert((std::is_same<decltype(std::vswscanf(L"", L"", va)), int>::value), "");
-    static_assert((std::is_same<decltype(std::vwprintf(L"", va)), int>::value), "");
-    static_assert((std::is_same<decltype(std::vwscanf(L"", va)), int>::value), "");
-    static_assert((std::is_same<decltype(std::wprintf(L"")), int>::value), "");
-    static_assert((std::is_same<decltype(std::wscanf(L"")), int>::value), "");
     static_assert((std::is_same<decltype(std::fgetwc(fp)), std::wint_t>::value), "");
     static_assert((std::is_same<decltype(std::fgetws(ws, 0, fp)), wchar_t*>::value), "");
     static_assert((std::is_same<decltype(std::fputwc(L' ', fp)), std::wint_t>::value), "");
     static_assert((std::is_same<decltype(std::fputws(L"", fp)), int>::value), "");
     static_assert((std::is_same<decltype(std::fwide(fp, 0)), int>::value), "");
     static_assert((std::is_same<decltype(std::getwc(fp)), std::wint_t>::value), "");
-    static_assert((std::is_same<decltype(std::getwchar()), std::wint_t>::value), "");
     static_assert((std::is_same<decltype(std::putwc(L' ', fp)), std::wint_t>::value), "");
-    static_assert((std::is_same<decltype(std::putwchar(L' ')), std::wint_t>::value), "");
     static_assert((std::is_same<decltype(std::ungetwc(L' ', fp)), std::wint_t>::value), "");
     static_assert((std::is_same<decltype(std::wcstod(L"", (wchar_t**)0)), double>::value), "");
     static_assert((std::is_same<decltype(std::wcstof(L"", (wchar_t**)0)), float>::value), "");
@@ -106,4 +100,16 @@ int main()
     static_assert((std::is_same<decltype(std::wcrtomb(ns, L' ', &mb)), std::size_t>::value), "");
     static_assert((std::is_same<decltype(std::mbsrtowcs(ws, (const char**)0, s, &mb)), std::size_t>::value), "");
     static_assert((std::is_same<decltype(std::wcsrtombs(ns, (const wchar_t**)0, s, &mb)), std::size_t>::value), "");
+
+#ifndef _LIBCPP_HAS_NO_STDIN
+    static_assert((std::is_same<decltype(std::getwchar()), std::wint_t>::value), "");
+    static_assert((std::is_same<decltype(std::vwscanf(L"", va)), int>::value), "");
+    static_assert((std::is_same<decltype(std::wscanf(L"")), int>::value), "");
+#endif
+
+#ifndef _LIBCPP_HAS_NO_STDOUT
+    static_assert((std::is_same<decltype(std::putwchar(L' ')), std::wint_t>::value), "");
+    static_assert((std::is_same<decltype(std::vwprintf(L"", va)), int>::value), "");
+    static_assert((std::is_same<decltype(std::wprintf(L"")), int>::value), "");
+#endif
 }