I'm making a simple threaded server application in C++, thing is, I use libconfig++ to parse my configuration files. Well, libconfig doesn't support multithreading, thus I'm using two wrapper classes in order to accomplish "support". Point is, one of them fails:
class app_config {
friend class app_config_lock;
public:
app_config(char *file) :
cfg(new libconfig::Config()),
mutex(new boost::mutex())
{
cfg->readFile(file);
}
private:
boost::shared_ptr<libconfig::Config> cfg;
boost::shared_ptr<boost::mutex> mutex;
};
Fails horribly when called from my main.cpp file:
app_main::app_main(int c, char **v) : argc(c), argv(v) {
// here need code to parse arguments and pass configuration file!.
try {
config = app_config("mscs.cfg");
} catch (libconfig::ParseException &e) {
cout << "Parse error at line " << e.getLine() << ": " << e.getError() << endl;
throw;
} catch (libconfig::FileIOException &e) {
cout << "Configuration file not found." << endl;
throw;
}
}
And it says:
main.cpp: In constructor ‘app_main::app_main(int, char**)’:
main.cpp:38:54: error: no matching function for call to ‘app_config::app_config()’
main.cpp:38:54: note: candidates are:
../include/app_config.h:15:5: note: app_config::app_config(char*)
../include/app_config.h:15:5: note: candidate expects 1 argument, 0 provided
../include/app_config.h:12:7: note: app_config::app_config(const app_config&)
../include/app_config.h:12:7: note: candidate expects 1 argument, 0 provided
main.cpp:41:39: warning: deprecated conversion from string constant to ‘char*’ [-Wwrite-strings] (THIS CAN BE IGNORED, I WAS USING STD::STRING, YET CHANGED IT FOR TESTING PURPOSES)
Which is weird because I'm clearly passing an argument, and moreover its a char *
!.
Well, as always, any help will be appreciated.
Julian.
You're trying to default-construct your config, and then assign to it later. But you don't have a default constructor.
The correct way to pass an argument to the constructor of a member variable is:
app_main::app_main(int c, char **v) : argc(c), argv(v), config("mscs.cfg")
You can still trap the exception, by using what's known as a function try-block. See http://www.gotw.ca/gotw/066.htm
Final code:
app_main::app_main(int c, char **v)
try : argc(c), argv(v), config("mscs.cfg")
{
// more constructor logic here
} catch (libconfig::ParseException &e) {
cout << "Parse error at line " << e.getLine() << ": " << e.getError() << endl;
throw;
} catch (libconfig::FileIOException &e) {
cout << "Configuration file not found." << endl;
throw;
}