I can't use spdlog loggers in a loop

Question

I want to create log over a loop. Here is a simple exampe:

#include <iostream>
#include "logging.hpp"

int main(int argc,char* argv[]){

        for(int i=1; i<argc; i++)
                Logger l(argv[i]);
        return 0;
}

And this is logging.hpp file content :

#include "spdlog/spdlog.h"
#include "spdlog/sinks/stdout_color_sinks.h"
#include <iostream>

class Logger{
        public:
                Logger(std::string msg){
                        auto console = spdlog::stdout_color_mt("console");
                        console->info(msg);
                }
};

it compiles with no problem but when I run program with more than one arguments it occurs error:

[2020-10-14 20:12:30.067] [console] [info] .<first-argument>
terminate called after throwing an instance of 'spdlog::spdlog_ex'
  what():  logger with name 'console' already exists
Aborted (core dumped)

I think the error message is clear : you're only allowed to create one instance. You could make the `console` logger `static`, for example. That will ensure there's only one instance in the entire program named "console" — Botje, Oct 14 '20 at 16:47
Are you trying to log multiple messages to `ONE` log, or to create multiple logs and write one message to each (as you do now)? — Vlad Feinstein, Oct 14 '20 at 17:04

score 2 · Accepted Answer · answered Oct 14 '20 at 17:02

2

The very quick and dirty fix is to do:

static auto console = spdlog::stdout_color_mt("console");

This will ensure there is only ever one instance, as the initializer is executed exactly once.

answered Oct 14 '20 at 17:02

Botje

26,269
3
31
41

I find your solution quick and clean :) (If that's what OP wanted) – Vlad Feinstein Oct 14 '20 at 17:06
Why it's dirty? – Amir reza Riahi Oct 14 '20 at 17:07
1

Generally you want to configure loggers before you start using them, this implicit initialization makes that harder to get right. – Botje Oct 14 '20 at 17:09

I can't use spdlog loggers in a loop

1 Answers1