Add support for programmatically providing runtime values for configuration option values (#520)

* Configuration ${varname} values can be set programatically prior to loading a configuration file

* The current executable's file name and its components are available for use in a configuration file
and the LOG4CXX_CONFIGURATION environment variable

* Simplify multiprocessrollingtest

* Update to latest version of vcpkg

* Also start a watchdog when using DefaultConfigurator::configureFromFile

* Support for disabling the expansion of ${varname} instances in LOG4CXX_CONFIGURATION environment variable

* Update config3.cpp for MacOS 15

* Prevent MacOS 14 failure by installing CMake from brew to 'force' the usage of CMake Version 4 when using g++ on MacOS

* The Configurator implementation is responsible for doing 'repository->setConfigured(true)'

* Always warn when the configuration file exists and cannot be used

* Use DefaultConfigurator::configureFromFile in a unit test

* Ensure unit test work when std::filesystem::path is unavailable an when logchar_t != char

* Improve unit test completeness/robustness

* Fix compilation error

* Ensure FileWatchdog::checkAndConfigure always calls doOnChange() after FileWatchdog::setFile()

* Always return the name of the found configuration file from configureFromFile

* Show the combinatorial behaviour of DefaultConfigurator::configureFromFile more explicitly

Author: swebb2066

.github/workflows/log4cxx-macos.yml

@@ -56,6 +56,9 @@ jobs:
         if [ ${{ matrix.os }} != macos-13 ]; then brew install apr-util; fi
         if [ ${{ matrix.odbc }} == ON ]; then brew install unixodbc; fi
         if [ ${{ matrix.qt }} == ON ]; then brew install qt; fi
+        if [ ${{ matrix.cxx }} == "g++-14" -a $(cmake --version | head -1 | awk '{split($3, a, "."); print a[1]}') -lt 4 ]
+        then brew install cmake ninja
+        fi
 
     - name: 'configure and build'
       run: |

.github/workflows/log4cxx-windows-static.yml

@@ -50,7 +50,7 @@ jobs:
       with:
         repository: microsoft/vcpkg
         path: vcpkg
-        ref: 2024.01.12
+        ref: 2025.07.25
 
     - name: 'Configure Dependencies'
       if: steps.restore-vcpkg-cache.outputs.cache-hit != 'true'

.github/workflows/log4cxx-windows.yml

@@ -50,7 +50,7 @@ jobs:
       with:
         repository: microsoft/vcpkg
         path: vcpkg
-        ref: 2024.01.12
+        ref: 2025.07.25
 
     - name: 'Configure Dependencies'
       if: steps.restore-vcpkg-cache.outputs.cache-hit != 'true'

CMakeLists.txt

@@ -109,6 +109,13 @@ else()
     set(ENABLE_FMT_LAYOUT "OFF")
 endif()
 
+option(LOG4CXX_CONFIG_VAR_EXPANSION "Expand \${varname} instances in LOG4CXX_CONFIGURATION" ON)
+if(LOG4CXX_CONFIG_VAR_EXPANSION)
+    set(EXPAND_CONFIG_ENV_VAR 1)
+else()
+    set(EXPAND_CONFIG_ENV_VAR 0)
+endif(LOG4CXX_CONFIG_VAR_EXPANSION)
+
 # Request C++20, if available
 # This *should* fallback to an older standard if it is not available
 if( NOT "${CMAKE_CXX_STANDARD}")

src/examples/cpp/CMakeLists.txt

@@ -46,7 +46,7 @@ foreach(exampleName IN LISTS ALL_LOG4CXX_EXAMPLES)
         target_link_libraries(${PROGRAM_NAME} PRIVATE log4cxx-qt)
     endif()
     if(${exampleName} STREQUAL auto-configured)
-        target_sources(${PROGRAM_NAME} PRIVATE com/foo/config3.cpp )
+        target_sources(${PROGRAM_NAME} PRIVATE com/foo/config4.cpp )
     endif()
     target_compile_definitions(${PROGRAM_NAME} PRIVATE ${EXAMPLE_COMPILE_DEFINITIONS} ${LOG4CXX_COMPILE_DEFINITIONS} ${APR_COMPILE_DEFINITIONS} ${APR_UTIL_COMPILE_DEFINITIONS} )
     target_include_directories(${PROGRAM_NAME} PRIVATE ${CMAKE_CURRENT_LIST_DIR} $<TARGET_PROPERTY:log4cxx,INCLUDE_DIRECTORIES>)

src/examples/cpp/auto-configured.xml

@@ -3,7 +3,7 @@
   <appender name="ConsoleAppender" class="org.apache.log4j.ConsoleAppender">
     <param name="Target" value="System.out"/>
     <layout class="org.apache.log4j.PatternLayout">
-      <param name="ConversionPattern" value="[%d{yyyy-MM-dd HH:mm:ss}] %c %-5p - %m%n"/>
+      <param name="ConversionPattern" value="${CURRENT_VENDOR_FOLDER}.${CURRENT_PRODUCT_FOLDER}: [%d{yyyy-MM-dd HH:mm:ss}]  %c %-5p - %m%n"/>
     </layout>
   </appender>
 

src/examples/cpp/com/foo/config3.cpp

@@ -52,6 +52,7 @@ auto DefaultConfigurationFileNames(std::string& altPrefix) -> std::vector<std::s
 	GetModuleFileName(NULL, buf, bufSize);
 	pathSepar = '\\';
 #elif defined(__APPLE__)
+	bufCount = bufSize;
 	_NSGetExecutablePath(buf, &bufCount);
 #elif (defined(_XOPEN_SOURCE) && _XOPEN_SOURCE >= 500) || (defined(_POSIX_C_SOURCE) && _POSIX_C_SOURCE >= 200112L)
 	std::ostringstream exeLink;

src/examples/cpp/com/foo/config4.cpp

@@ -0,0 +1,72 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+#include "config.h"
+#include "product_version.h" // Provides getVendorFolder() and getProductFolder()
+#include <log4cxx/logmanager.h>
+#include <log4cxx/defaultconfigurator.h>
+#include <log4cxx/basicconfigurator.h>
+#include <log4cxx/helpers/transcoder.h>
+#include <vector>
+
+namespace com { namespace foo {
+
+// Retrieve the \c name logger pointer.
+// Configure Log4cxx on the first call.
+auto getLogger(const std::string& name) -> LoggerPtr {
+	using namespace log4cxx;
+	static struct log4cxx_initializer {
+		log4cxx_initializer() {
+			auto vendorFolder = getVendorFolder();
+			auto productFolder = getProductFolder();
+			LOG4CXX_DECODE_CHAR(lsVendorFolder, vendorFolder);
+			LOG4CXX_DECODE_CHAR(lsProductFolder, productFolder);
+
+			// Allow expansion of ${CURRENT_VENDOR_FOLDER} and ${CURRENT_PRODUCT_FOLDER}
+			// when loading a configuration from a file
+			auto& props = spi::Configurator::properties();
+			props.setProperty(LOG4CXX_STR("CURRENT_VENDOR_FOLDER"), lsVendorFolder);
+			props.setProperty(LOG4CXX_STR("CURRENT_PRODUCT_FOLDER"), lsProductFolder);
+
+			// Check every 5 seconds for configuration file changes
+			DefaultConfigurator::setConfigurationWatchSeconds(5);
+
+			// Look for a configuration file in the current working directory
+			// and the same directory as the program
+			std::vector<LogString> paths
+				{ LOG4CXX_STR(".")
+				, LOG4CXX_STR("${PROGRAM_FILE_PATH.PARENT_PATH}")
+				};
+			std::vector<LogString> names
+				{ LOG4CXX_STR("${PROGRAM_FILE_PATH.STEM}.xml")
+				, LOG4CXX_STR("${PROGRAM_FILE_PATH.STEM}.properties")
+				};
+			auto status       = spi::ConfigurationStatus::NotConfigured;
+			auto selectedPath = LogString();
+			std::tie(status, selectedPath) = DefaultConfigurator::configureFromFile(paths, names);
+			if (status == spi::ConfigurationStatus::NotConfigured)
+				BasicConfigurator::configure(); // Send events to the console
+		}
+		~log4cxx_initializer() {
+			LogManager::shutdown();
+		}
+	} initialiser;
+	return name.empty()
+		? LogManager::getRootLogger()
+		: LogManager::getLogger(name);
+}
+
+} } // namespace com::foo

src/examples/cpp/com/foo/product_version.h

@@ -0,0 +1,25 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+std::string getVendorFolder()
+{
+  return "ApacheSoftwareFoundation";
+}
+std::string getProductFolder()
+{
+  return "Logging";
+}

src/main/cpp/configurator.cpp

@@ -19,15 +19,44 @@
 #include <log4cxx/spi/configurator.h>
 #include <assert.h>
 #include <log4cxx/logger.h>
+#include <log4cxx/helpers/singletonholder.h>
+#include <log4cxx/helpers/system.h>
+
+#if !defined(LOG4CXX)
+	#define LOG4CXX 1
+#endif
+#include <log4cxx/helpers/aprinitializer.h>
 
 using namespace LOG4CXX_NS;
 using namespace LOG4CXX_NS::spi;
 
 IMPLEMENT_LOG4CXX_OBJECT(Configurator)
 
 
+namespace
+{
+	struct ConfiguratorTag {};
+	using ConfiguratorProperties = std::pair<ConfiguratorTag, helpers::Properties>;
 
+	ConfiguratorProperties& getInstance()
+	{
+		using ConfiguratorObject = helpers::SingletonHolder<ConfiguratorProperties>;
+		auto result = helpers::APRInitializer::getOrAddUnique<ConfiguratorObject>
+			( []() -> helpers::ObjectPtr
+				{ return std::make_shared<ConfiguratorObject>(); }
+			);
+		return result->value();
+	}
+}
 
 Configurator::Configurator()
 {
 }
+
+helpers::Properties& Configurator::properties()
+{
+	auto& result = getInstance().second;
+	if (result.isEmpty())
+		helpers::System::addProgramFilePathComponents(result);
+	return result;
+}