Remove arithmetic +/-127 on chars; results in UB when dealing with signed chars. Thanks to STL@microsoft for the report.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@271897 91177308-0d34-0410-b5e6-96231b3b80d8

test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char/lt.pass.cpp

@@ -1,6 +1,6 @@
 //===----------------------------------------------------------------------===//
 //
-//                     The LLVM Compiler Infrastructure
+//					   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.
@@ -18,11 +18,16 @@
 
 int main()
 {
-    char c = '\0';
-    assert(!std::char_traits<char>::lt('a', 'a'));
-    assert( std::char_traits<char>::lt('A', 'a'));
-    assert(!std::char_traits<char>::lt('A' + 127, 'a'));
-    assert(!std::char_traits<char>::lt('A' - 127, 'a'));
-    assert( std::char_traits<char>::lt('A', 'a' + 127));
-    assert( std::char_traits<char>::lt('A', 'a' - 127));
+	assert( std::char_traits<char>::lt('\0', 'A'));
+	assert(!std::char_traits<char>::lt('A', '\0'));
+
+	assert(!std::char_traits<char>::lt('a', 'a'));
+	assert( std::char_traits<char>::lt('A', 'a'));
+	assert(!std::char_traits<char>::lt('a', 'A'));
+	
+	assert( std::char_traits<char>::lt('a', 'z'));
+	assert( std::char_traits<char>::lt('A', 'Z'));
+
+	assert( std::char_traits<char>::lt(' ', 'A'));
+	assert( std::char_traits<char>::lt('A', '~'));
 }