Fix C++20 compatibility bug.

This was shown to work for C++14, C++17, and C++20 after patched into googletest for the protobuf repo's CI.

Closes #3659

PiperOrigin-RevId: 544795507
Change-Id: I3e0a94f675e78a6ee9aeccae86c23d940efed8eb

Author: mkruskal-google

googletest/include/gtest/gtest-printers.h

@@ -475,7 +475,7 @@ GTEST_API_ void PrintTo(char32_t c, ::std::ostream* os);
 inline void PrintTo(char16_t c, ::std::ostream* os) {
   PrintTo(ImplicitCast_<char32_t>(c), os);
 }
-#ifdef __cpp_char8_t
+#ifdef __cpp_lib_char8_t
 inline void PrintTo(char8_t c, ::std::ostream* os) {
   PrintTo(ImplicitCast_<char32_t>(c), os);
 }
@@ -588,7 +588,7 @@ inline void PrintTo(const unsigned char* s, ::std::ostream* os) {
 inline void PrintTo(unsigned char* s, ::std::ostream* os) {
   PrintTo(ImplicitCast_<const void*>(s), os);
 }
-#ifdef __cpp_char8_t
+#ifdef __cpp_lib_char8_t
 // Overloads for u8 strings.
 GTEST_API_ void PrintTo(const char8_t* s, ::std::ostream* os);
 inline void PrintTo(char8_t* s, ::std::ostream* os) {
@@ -908,7 +908,7 @@ void UniversalPrintArray(const T* begin, size_t len, ::std::ostream* os) {
 GTEST_API_ void UniversalPrintArray(const char* begin, size_t len,
                                     ::std::ostream* os);
 
-#ifdef __cpp_char8_t
+#ifdef __cpp_lib_char8_t
 // This overload prints a (const) char8_t array compactly.
 GTEST_API_ void UniversalPrintArray(const char8_t* begin, size_t len,
                                     ::std::ostream* os);

googletest/include/gtest/internal/gtest-port.h

@@ -1998,7 +1998,7 @@ inline bool IsUpper(char ch) {
 inline bool IsXDigit(char ch) {
   return isxdigit(static_cast<unsigned char>(ch)) != 0;
 }
-#ifdef __cpp_char8_t
+#ifdef __cpp_lib_char8_t
 inline bool IsXDigit(char8_t ch) {
   return isxdigit(static_cast<unsigned char>(ch)) != 0;
 }

googletest/src/gtest-printers.cc

@@ -216,7 +216,7 @@ static const char* GetCharWidthPrefix(signed char) { return ""; }
 
 static const char* GetCharWidthPrefix(unsigned char) { return ""; }
 
-#ifdef __cpp_char8_t
+#ifdef __cpp_lib_char8_t
 static const char* GetCharWidthPrefix(char8_t) { return "u8"; }
 #endif
 
@@ -232,7 +232,7 @@ static CharFormat PrintAsStringLiteralTo(char c, ostream* os) {
   return PrintAsStringLiteralTo(ToChar32(c), os);
 }
 
-#ifdef __cpp_char8_t
+#ifdef __cpp_lib_char8_t
 static CharFormat PrintAsStringLiteralTo(char8_t c, ostream* os) {
   return PrintAsStringLiteralTo(ToChar32(c), os);
 }
@@ -395,7 +395,7 @@ void UniversalPrintArray(const char* begin, size_t len, ostream* os) {
   UniversalPrintCharArray(begin, len, os);
 }
 
-#ifdef __cpp_char8_t
+#ifdef __cpp_lib_char8_t
 // Prints a (const) char8_t array of 'len' elements, starting at address
 // 'begin'.
 void UniversalPrintArray(const char8_t* begin, size_t len, ostream* os) {
@@ -438,7 +438,7 @@ void PrintCStringTo(const Char* s, ostream* os) {
 
 void PrintTo(const char* s, ostream* os) { PrintCStringTo(s, os); }
 
-#ifdef __cpp_char8_t
+#ifdef __cpp_lib_char8_t
 void PrintTo(const char8_t* s, ostream* os) { PrintCStringTo(s, os); }
 #endif