enh(cmake): Add option POCO_ENABLE_CPP20 to enable C++20 when compiling Poco (#4956)

* enh(cmake): Add option POCO_CXX20 to enable standard C++20 and related changes.

* chore(cmake): do not allow C++20 setting for compilers that do not support it properly.

* fix(NetSSL_Win): indentation.

CMakeLists.txt

@@ -36,18 +36,48 @@ list(APPEND CMAKE_MODULE_PATH ${CMAKE_CURRENT_SOURCE_DIR}/cmake)
 # Setup C/C++ compiler options
 #################################################################################
 
-# C++17 compiler flags
+# Detect if compiler supports at least C++17 standard
 include(CXX1x)
 check_for_cxx17_compiler(CXX17_COMPILER)
 
-# If a C++17 compiler is available, then set the appropriate flags
-if(CXX17_COMPILER)
-	set(CMAKE_CXX_STANDARD 17)
-	set(CMAKE_CXX_STANDARD_REQUIRED ON)
-else()
+if(NOT CXX17_COMPILER)
 	message(FATAL_ERROR "Compiler does not support C++17.")
 endif()
 
+# If a C++17 compiler is available, then set the appropriate flags
+
+option(POCO_ENABLE_CPP20 "Build Poco with C++20 standard" ON)
+
+if (EMSCRIPTEN)
+	set(POCO_ENABLE_CPP20 OFF CACHE BOOL "Build Poco with C++20 standard" FORCE)
+else()
+
+# https://libcxx.llvm.org/Status/Cxx20.html
+# https://en.wikipedia.org/wiki/Xcode#Toolchain_versions
+
+	if (CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
+		if (CMAKE_CXX_COMPILER_VERSION VERSION_LESS 18.0)
+			# Does not fully support C++20 yet
+			set(POCO_ENABLE_CPP20 OFF CACHE BOOL "Build Poco with C++20 standard" FORCE)
+		endif ()
+	elseif (CMAKE_CXX_COMPILER_ID STREQUAL "AppleClang")
+		if (CMAKE_CXX_COMPILER_VERSION VERSION_LESS 17.0)
+			# Does not fully support C++20 yet
+			set(POCO_ENABLE_CPP20 OFF CACHE BOOL "Build Poco with C++20 standard" FORCE)
+		endif ()
+	endif()
+endif()
+
+if (POCO_ENABLE_CPP20)
+	set(CMAKE_CXX_STANDARD 20)
+	message(STATUS "Building Poco with C++20 standard")
+else()
+	set(CMAKE_CXX_STANDARD 17)
+	message(STATUS "Building Poco with C++17 standard")
+endif()
+set(CMAKE_CXX_STANDARD_REQUIRED ON)
+
+
 if(NOT CMAKE_BUILD_TYPE)
 	set(CMAKE_BUILD_TYPE "RelWithDebInfo")
 endif()

Foundation/CMakeLists.txt

@@ -128,17 +128,33 @@ target_include_directories(Foundation
 target_compile_definitions(Foundation
 	PUBLIC
 		$<$<CONFIG:Debug>:_DEBUG>
-		$<$<BOOL:${DISABLE_CPP14}>:POCO_DISABLE_CPP14>
-		$<$<NOT:$<BOOL:${DISABLE_CPP14}>>:POCO_ENABLE_CPP14>
-		$<$<BOOL:${DISABLE_CPP11}>:POCO_DISABLE_CPP11>
-		$<$<NOT:$<BOOL:${DISABLE_CPP11}>>:POCO_ENABLE_CPP11>
+		$<$<BOOL:${POCO_ENABLE_CPP20}>:POCO_ENABLE_CPP20>
 )
 target_compile_features(Foundation
 	PUBLIC
 		$<$<NOT:$<BOOL:${DISABLE_CPP11}>>:cxx_defaulted_move_initializers>
 )
-if(NOT DISABLE_CPP14 AND CMAKE_VERSION VERSION_GREATER "3.8")
-	target_compile_features(Foundation PUBLIC cxx_std_14)
+
+#
+# Set target C++ standard compile features for exported target.
+#
+target_compile_features(Foundation PUBLIC cxx_std_17)
+if (POCO_ENABLE_CPP20)
+	target_compile_features(Foundation PUBLIC cxx_std_20)
+endif()
+
+if (POCO_ENABLE_CPP20 AND NOT EMSCRIPTEN)
+	if (CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
+		if (CMAKE_CXX_COMPILER_VERSION VERSION_LESS 20.0)
+			# Some C++20 features must be enabled explicitly in clang
+			target_compile_options(Foundation PUBLIC -fexperimental-library)
+		endif ()
+	elseif (CMAKE_CXX_COMPILER_ID STREQUAL "AppleClang")
+		if (CMAKE_CXX_COMPILER_VERSION VERSION_LESS 18.0)
+			# Some C++20 features must be enabled explicitly in clang
+			target_compile_options(Foundation PUBLIC -fexperimental-library)
+		endif ()
+	endif()
 endif()
 
 if(NOT BUILD_SHARED_LIBS)

Foundation/include/Poco/Config.h

@@ -186,6 +186,8 @@
 #endif
 
 #define POCO_HAVE_CPP17_COMPILER (__cplusplus >= 201703L)
+#define POCO_HAVE_CPP20_COMPILER (__cplusplus >= 202002L)
+#define POCO_HAVE_CPP23_COMPILER (__cplusplus >= 202302L)
 
 // Option to silence deprecation warnings.
 #ifndef POCO_SILENCE_DEPRECATED

Foundation/include/Poco/UTFString.h

@@ -260,12 +260,6 @@ struct UTF32CharTraits
 };
 
 
-//#if defined(POCO_ENABLE_CPP11) //TODO
-	//	using char16_t       UTF16Char;
-	//	using std::u16string UTF16String;
-	//	using char32_t       UTF32Char;
-	//	using std::u32string UTF32String;
-//#else
 	#ifdef POCO_NO_WSTRING
 		using UTF16Char = Poco::UInt16;
 		using UTF16String = std::basic_string<UTF16Char, UTF16CharTraits>;
@@ -301,7 +295,6 @@ struct UTF32CharTraits
 			#define POCO_USE_STRING16
 		#endif //POCO_OS_FAMILY_WINDOWS
 	#endif //POCO_NO_WSTRING
-//#endif // POCO_ENABLE_CPP11
 
 
 } // namespace Poco

Foundation/src/Format.cpp

@@ -252,23 +252,23 @@ namespace
 std::string format(const std::string& fmt, const Any& value)
 {
 	std::string result;
-	format(result, fmt, value);
+	Poco::format(result, fmt, value);
 	return result;
 }
 
 
 void format(std::string& result, const char *fmt, const std::vector<Any>& values)
 {
-	format(result, std::string(fmt), values);
+	Poco::format(result, std::string(fmt), values);
 }
 
 
 void format(std::string& result, const std::string& fmt, const std::vector<Any>& values)
 {
-	std::string::const_iterator itFmt  = fmt.begin();
-	std::string::const_iterator endFmt = fmt.end();
-	std::vector<Any>::const_iterator itVal  = values.begin();
-	std::vector<Any>::const_iterator endVal = values.end();
+	auto itFmt  = fmt.begin();
+	const auto endFmt = fmt.end();
+	auto itVal  = values.begin();
+	const auto endVal = values.end();
 	while (itFmt != endFmt)
 	{
 		switch (*itFmt)
@@ -283,7 +283,7 @@ void format(std::string& result, const std::string& fmt, const std::vector<Any>&
 					std::size_t index = parseIndex(itFmt, endFmt);
 					if (index < values.size())
 					{
-						std::vector<Any>::const_iterator it = values.begin() + index;
+						auto it = values.begin() + index;
 						formatOne(result, itFmt, endFmt, it);
 					}
 					else throw InvalidArgumentException("format argument index out of range", fmt);

Foundation/testsuite/src/AnyTest.cpp

@@ -233,7 +233,7 @@ void AnyTest::testAnySwap()
 		Poco::UInt64 eight = 8;
 		Poco::UInt64 nine = 9;
 
-		bool operator==(const BigObject& other)
+		bool operator==(const BigObject& other) const
 		{
 			return one == other.one &&
 				two == other.two &&

Foundation/testsuite/src/FormatTest.cpp

@@ -29,9 +29,7 @@ FormatTest::FormatTest(const std::string& name): CppUnit::TestCase(name)
 }
 
 
-FormatTest::~FormatTest()
-{
-}
+FormatTest::~FormatTest() = default;
 
 
 void FormatTest::testChar()
@@ -256,7 +254,7 @@ void FormatTest::testBool()
 	bv.push_back(true);
 
 	s.clear();
-	format(s, "%b%b%b%b%b%b%b%b%b%b", bv);
+	Poco::format(s, "%b%b%b%b%b%b%b%b%b%b", bv);
 	assertTrue (s == "0101010101");
 }
 
@@ -571,7 +569,7 @@ void FormatTest::testAny()
 
 	s.clear();
 	std::vector<Any> av{ 42, std::string("42"), 42. };
-	format(s, "%d '%s' %f", av);
+	Poco::format(s, "%d '%s' %f", av);
 	assertTrue (s.find("42 '42' 42.0") == 0);
 }
 

Net/src/SSPINTLMCredentials.cpp

@@ -69,7 +69,8 @@ public:
 	bool available()
 	{
 		PSecPkgInfoW pSecPkgInfo;
-		SECURITY_STATUS status = _pSecFunTable->QuerySecurityPackageInfoW(L"NTLM", &pSecPkgInfo);
+		::SEC_WCHAR package[] = L"NTLM";
+		SECURITY_STATUS status = _pSecFunTable->QuerySecurityPackageInfoW(package, &pSecPkgInfo);
 		if (status == SEC_E_OK)
 		{
 			_pSecFunTable->FreeContextBuffer(pSecPkgInfo);
@@ -81,7 +82,8 @@ public:
 	Poco::SharedPtr<NTLMContext> createNTLMContext(const std::string& host, const std::string& service)
 	{
 		PSecPkgInfoW pSecPkgInfo;
-		SECURITY_STATUS status = _pSecFunTable->QuerySecurityPackageInfoW(L"NTLM", &pSecPkgInfo);
+		::SEC_WCHAR package[] = L"NTLM";
+		SECURITY_STATUS status = _pSecFunTable->QuerySecurityPackageInfoW(package, &pSecPkgInfo);
 		if (status != SEC_E_OK) throw Poco::SystemException("NTLM SSPI not available", status);
 
 		std::size_t maxTokenSize = pSecPkgInfo->cbMaxToken;
@@ -93,7 +95,7 @@ public:
 		TimeStamp expiry;
 		status = _pSecFunTable->AcquireCredentialsHandleW(
 			NULL,
-			L"NTLM",
+			package,
 			SECPKG_CRED_OUTBOUND,
 			NULL,
 			NULL,

NetSSL_Win/src/Context.cpp

@@ -174,8 +174,10 @@ void Context::loadCertificate()
 	}
 	if (!_hCertStore) throw CertificateException("Failed to open certificate store", _certStoreName, GetLastError());
 
+
 	CERT_RDN_ATTR cert_rdn_attr;
-	cert_rdn_attr.pszObjId = szOID_COMMON_NAME;
+	char cmnName[] = szOID_COMMON_NAME;
+	cert_rdn_attr.pszObjId = cmnName;
 	cert_rdn_attr.dwValueType = CERT_RDN_ANY_TYPE;
 	cert_rdn_attr.Value.cbData = (DWORD) _certNameOrPath.size();
 	cert_rdn_attr.Value.pbData = (BYTE *) _certNameOrPath.c_str();
@@ -270,7 +272,7 @@ void Context::acquireSchannelCredentials(CredHandle& credHandle) const
 	if (_pCert)
 	{
 		schannelCred.cCreds = 1; // how many cred are stored in &pCertContext
-		schannelCred.paCred = &const_cast<PCCERT_CONTEXT>(_pCert);
+        schannelCred.paCred = const_cast<PCCERT_CONTEXT*>(&_pCert);
 	}
 
 	schannelCred.grbitEnabledProtocols = proto();
@@ -312,9 +314,10 @@ void Context::acquireSchannelCredentials(CredHandle& credHandle) const
 
 	TimeStamp tsExpiry;
 	tsExpiry.LowPart = tsExpiry.HighPart = 0;
+    ::SEC_WCHAR name[] = UNISP_NAME_W;
 	SECURITY_STATUS status = _securityFunctions.AcquireCredentialsHandleW(
 		NULL,
-		UNISP_NAME_W,
+        name,
 		isForServerUse() ? SECPKG_CRED_INBOUND : SECPKG_CRED_OUTBOUND,
 		NULL,
 		&schannelCred,

NetSSL_Win/src/X509Certificate.cpp

@@ -396,7 +396,8 @@ void X509Certificate::loadCertificate(const std::string& certName, const std::st
 	if (!hCertStore) throw CertificateException("Failed to open certificate store", certStoreName, GetLastError());
 
 	CERT_RDN_ATTR cert_rdn_attr;
-	cert_rdn_attr.pszObjId = szOID_COMMON_NAME;
+	char cmnName[] = szOID_COMMON_NAME;
+	cert_rdn_attr.pszObjId = cmnName;
 	cert_rdn_attr.dwValueType = CERT_RDN_ANY_TYPE;
 	cert_rdn_attr.Value.cbData = static_cast<DWORD>(certName.size());
 	cert_rdn_attr.Value.pbData = reinterpret_cast<BYTE*>(const_cast<char*>(certName.c_str()));

Util/src/ServerApplication.cpp

@@ -333,7 +333,8 @@ int ServerApplication::run(int argc, wchar_t** argv)
 bool ServerApplication::isService()
 {
 	SERVICE_TABLE_ENTRYW svcDispatchTable[2];
-	svcDispatchTable[0].lpServiceName = L"";
+	wchar_t name[] = L"";
+	svcDispatchTable[0].lpServiceName = name;
 	svcDispatchTable[0].lpServiceProc = ServiceMain;
 	svcDispatchTable[1].lpServiceName = NULL;
 	svcDispatchTable[1].lpServiceProc = NULL;

cmake/CXX1x.cmake

@@ -22,9 +22,15 @@
 macro(check_for_cxx17_compiler _VAR)
 	message(STATUS "Checking for C++17 compiler")
 	set(${_VAR})
-    try_compile(_COMPILER_TEST_RESULT ${PROJECT_BINARY_DIR} ${PROJECT_SOURCE_DIR}/cmake/test_compiler.cpp CMAKE_FLAGS -DCMAKE_CXX_STANDARD=17 -DCMAKE_CXX_STANDARD_REQUIRED=ON)
+	try_compile(
+		_COMPILER_TEST_RESULT ${PROJECT_BINARY_DIR} ${PROJECT_SOURCE_DIR}/cmake/test_compiler.cpp
+		CMAKE_FLAGS -DCMAKE_CXX_STANDARD=17 -DCMAKE_CXX_STANDARD_REQUIRED=ON
+	)
 	if(NOT _COMPILER_TEST_RESULT AND CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
-      try_compile(_COMPILER_TEST_RESULT ${PROJECT_BINARY_DIR} ${PROJECT_SOURCE_DIR}/cmake/test_compiler.cpp CMAKE_FLAGS -DCMAKE_CXX_FLAGS="-stdlib=libc++" -DCMAKE_CXX_STANDARD=17 -DCMAKE_CXX_STANDARD_REQUIRED=ON)
+		try_compile(
+			_COMPILER_TEST_RESULT ${PROJECT_BINARY_DIR} ${PROJECT_SOURCE_DIR}/cmake/test_compiler.cpp
+			CMAKE_FLAGS -DCMAKE_CXX_FLAGS="-stdlib=libc++" -DCMAKE_CXX_STANDARD=17 -DCMAKE_CXX_STANDARD_REQUIRED=ON
+		)
 		if(_COMPILER_TEST_RESULT)
 			set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -stdlib=libc++")
 		else()