[libc++] Implement P0487R1 - Fixing operator>>(basic_istream&, CharT*)

Summary:
Avoid buffer overflow by replacing the pointer interface with an array reference interface in C++2a.
Tentatively ready on Batavia2018.

 https://wg21.link/lwg2499
 https://wg21.link/p0487

Reviewers: mclow.lists, ldionne, EricWF

Reviewed By: ldionne

Subscribers: libcxx-commits, cfe-commits, christof

Differential Revision: https://reviews.llvm.org/D51268

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@347377 91177308-0d34-0410-b5e6-96231b3b80d8

test/std/input.output/iostream.format/input.streams/istream.formatted/istream_extractors/signed_char_pointer.pass.cpp

@@ -61,6 +61,17 @@ int main()
         assert(std::string((char*)s) == "abc");
         assert(is.width() == 0);
     }
+#if TEST_STD_VER > 17
+    {
+        testbuf<char> sb("   abcdefghijk    ");
+        std::istream is(&sb);
+        signed char s[4];
+        is >> s;
+        assert(!is.eof());
+        assert(!is.fail());
+        assert(std::string((char*)s) == "abc");
+    }
+#endif
     {
         testbuf<char> sb("   abcdefghijk");
         std::istream is(&sb);
@@ -82,4 +93,15 @@ int main()
         assert(std::string((char*)s) == "");
         assert(is.width() == 0);
     }
+#if TEST_STD_VER > 17
+    {
+        testbuf<char> sb("   abcdefghijk");
+        std::istream is(&sb);
+        signed char s[1];
+        is >> s;
+        assert(!is.eof());
+        assert( is.fail());
+        assert(std::string((char*)s) == "");
+    }
+#endif
 }

test/std/input.output/iostream.format/input.streams/istream.formatted/istream_extractors/unsigned_char_pointer.pass.cpp

@@ -61,6 +61,17 @@ int main()
         assert(std::string((char*)s) == "abc");
         assert(is.width() == 0);
     }
+#if TEST_STD_VER > 17
+    {
+        testbuf<char> sb("   abcdefghijk    ");
+        std::istream is(&sb);
+        unsigned char s[4];
+        is >> s;
+        assert(!is.eof());
+        assert(!is.fail());
+        assert(std::string((char*)s) == "abc");
+    }
+#endif
     {
         testbuf<char> sb("   abcdefghijk");
         std::istream is(&sb);
@@ -82,4 +93,15 @@ int main()
         assert(std::string((char*)s) == "");
         assert(is.width() == 0);
     }
+#if TEST_STD_VER > 17
+    {
+        testbuf<char> sb("   abcdefghijk");
+        std::istream is(&sb);
+        unsigned char s[1];
+        is >> s;
+        assert(!is.eof());
+        assert( is.fail());
+        assert(std::string((char*)s) == "");
+    }
+#endif
 }

test/std/input.output/iostream.format/input.streams/istream.formatted/istream_extractors/wchar_t_pointer.pass.cpp

@@ -50,6 +50,17 @@ int main()
         assert(!is.fail());
         assert(std::string(s) == "abcdefghijk");
     }
+#if TEST_STD_VER > 17
+    {
+        testbuf<char> sb("   abcdefghijk    ");
+        std::istream is(&sb);
+        char s[4];
+        is >> s;
+        assert(!is.eof());
+        assert(!is.fail());
+        assert(std::string(s) == "abc");
+    }
+#endif
     {
         testbuf<wchar_t> sb(L"   abcdefghijk    ");
         std::wistream is(&sb);
@@ -71,6 +82,17 @@ int main()
         assert(std::wstring(s) == L"abcdefghijk");
         assert(is.width() == 0);
     }
+#if TEST_STD_VER > 17
+    {
+        testbuf<wchar_t> sb(L"   abcdefghijk");
+        std::wistream is(&sb);
+        wchar_t s[4];
+        is >> s;
+        assert(!is.eof());
+        assert(!is.fail());
+        assert(std::wstring(s) == L"abc");
+    }
+#endif
     {
         testbuf<char> sb("   abcdefghijk");
         std::istream is(&sb);
@@ -82,4 +104,15 @@ int main()
         assert(std::string(s) == "");
         assert(is.width() == 0);
     }
+#if TEST_STD_VER > 17
+    {
+        testbuf<char> sb("   abcdefghijk");
+        std::istream is(&sb);
+        char s[1];
+        is >> s;
+        assert(!is.eof());
+        assert( is.fail());
+        assert(std::string(s) == "");
+    }
+#endif
 }