Fixing utf16 to utf8 bug where 0x10000 was accidentially bitwise OR'ed instead of added.

Author: stgates

Release/src/utilities/asyncrt_utils.cpp

@@ -387,7 +387,7 @@ std::string __cdecl conversions::utf16_to_utf8(const utf16string &w)
             uint32_t codePoint = highSurrogate - H_SURROGATE_START;
             codePoint <<= 10;
             codePoint |= lowSurrogate - L_SURROGATE_START;
-            codePoint |= SURROGATE_PAIR_START;
+            codePoint += SURROGATE_PAIR_START;
 
             // 4 bytes need using 21 bits
             dest.push_back(char((codePoint >> 18) | 0xF0));                 // leading 3 bits

Release/tests/functional/utils/strings.cpp

@@ -133,6 +133,20 @@ TEST(utf16_to_utf8)
 #else
     VERIFY_ARE_EQUAL(conversion.to_bytes(input), result);
 #endif
+
+    // surrogate pair - covering regression bug where 0x10000 was accidentally bitwise OR'ed instead of added.
+    input.clear();
+    input.push_back(0xD840);
+    input.push_back(0xDC00);
+    result = utility::conversions::utf16_to_utf8(input);
+#if defined(__GLIBCXX__)
+    VERIFY_ARE_EQUAL(240u, static_cast<unsigned char>(result[0]));
+    VERIFY_ARE_EQUAL(160u, static_cast<unsigned char>(result[1]));
+    VERIFY_ARE_EQUAL(128u, static_cast<unsigned char>(result[2]));
+    VERIFY_ARE_EQUAL(128u, static_cast<unsigned char>(result[3]));
+#else
+    VERIFY_ARE_EQUAL(conversion.to_bytes(input), result);
+#endif
 }
 
 TEST(utf8_to_utf16)