这个问题通常是由于缺少链接日志库引起的。您可以通过在主Makefile或在编译器字符串中添加-llog4cxx来修复它。

例如，在使用gcc编译器时，您可以这样编写：

g++ -o myprogram myprogram.cpp -llog4cxx

以下是在使用自定义策略和log4cxx 0.10.0版本时编写策略的示例代码：

#include #include #include #include #include

class MyCustomLogPolicy : public log4cxx::spi::LoggingEvent { public: MyCustomLogPolicy() {}

MyCustomLogPolicy(const log4cxx::LoggerPtr& logger,
          const log4cxx::LevelPtr& level,
          const log4cxx::String& message) :
          log4cxx::spi::LoggingEvent(logger, level, message) {}

MyCustomLogPolicy(const log4cxx::LoggerPtr& logger,
          const log4cxx::spi::LocationInfo& locationInfo,
          const log4cxx::LevelPtr& level,
          const log4cxx::String& message,
          const log4cxx::helpers::ThrowablePtr& throwable) :
          log4cxx::spi::LoggingEvent(logger, locationInfo, level, message, throwable) {}

virtual ~MyCustomLogPolicy() {}

virtual log4cxx::helpers::ObjectPtr getProperty(const log4cxx::String& name) const {
    return NULL;
}

virtual void getPropertyList(log4cxx::helpers::ObjectList& pList) const {}

virtual void setProperty(const log4cxx::String& name, const log4cxx::helpers::ObjectPtr& value) {}

virtual void readExternal(log4cxx::helpers::ObjectInput& in) throw (log4cxx::helpers::IOException, log4cxx::helpers::ClassNotFoundException) {}

virtual void writeExternal(log4cxx::helpers::ObjectOutput& out) const throw (log4cxx