I've committed changes that should restore the ability to use the <<
operator in the message fragment of LOGCXX_INFO and similar macros.
It had been removed 3 years ago when the ability to have both char*
and wchar_t* messages processed in the same log4cxx build since the
log4cxx 0.9.7 macro definition wasn't compatible with wchar_t based
messages.
The log4cxx 0.9.7 definition was:
#define LOG4CXX_INFO(logger, message) { \
if (logger->isInfoEnabled()) {\
::log4cxx::StringBuffer oss; \
oss << message; \
logger->forcedLog(::log4cxx::Level::INFO, oss.str(), __FILE__,
__LINE__); }}
where ::log4cxx::StringBuffer is effectively std::ostringstream.
The current SVN HEAD definition is:
#define LOG4CXX_INFO(logger, message) { \
if (logger->isInfoEnabled()) {\
::log4cxx::helpers::MessageBuffer buf; \
logger->forcedLog(::log4cxx::Level::getInfo(), buf.str
(buf << message), LOG4CXX_LOCATION); }}
The MessageBuffer class was designed specifically for this usage
pattern and hopefully the class and macro combine so that:
1. log requests using the << operator that worked in 0.9.7 still work
2. log requests that have a simple message (char*, std::string,
wchar_t*, std::wstring) work but avoid the overhead of
std::ostringstream construction (which can be surprisingly expensive)
3. log requests that are simply concatenation of strings using
operator<< also avoid std::ostringstream construction.
4. log requests that contain a ((char*) 0) or ((wchar_t*) 0) will be
converted to "null" when std::ostringstream construction is avoided.
5. log requests where the first part of the expression is wchar_t
based will use std::basic_ostringstream<wchar_t>.
So all the following should work as expected:
//
// no std::ostringstream construction
//
LOG4CXX_INFO(logger, "Hello");
LOG4CXX_INFO(logger, L"Hello");
LOG4CXX_INFO(logger, "Hello" << ", World");
LOG4CXX_INFO(logger, L"Hello" << L", World");
LOG4CXX_INFO(logger, "null:" << ((char*) 0)");
//
// uses std::ostringstream
//
LOG4CXX_INFO(logger, "Iteration " << i);
LOG4CXX_INFO(logger, std::scientific << "pi=" << 3.1415926);
//
// uses std::basic_ostringstream<wchar_t>
//
LOG4CXX_INFO(logger, L"Iteration " << i);
I haven't tried a Windows build yet which will have to wait till
tomorrow. I'd appreciate any feedback, particularly with any code
base that made extensive use of operator<< in messages.
If this works effectively, then we should remove LogStream from SVN
HEAD as it was never particularly satisfying. If somebody really
wants it to stay, we could leave it in and mark it deprecated.
