Why Qt Creator's application output does not print from spdlog logger

Question

I have working logging in Visual studio project using spdlog. I used the same project in Qt creator, then the spdlog logging does not output anything. But the std::cout still works and prints to Qt creator's application output window.

std::vector<spdlog::sink_ptr> sinks;
sinks.push_back(std::make_shared<spdlog::sinks::stdout_color_sink_mt>());
sinks.push_back(std::make_shared<spdlog::sinks::basic_file_sink_mt>("multisink.txt", true));
auto appLogger = std::make_shared<spdlog::logger>("appLogger", begin(sinks), end(sinks));
appLogger->set_level(spdlog::level::debug);
spdlog::register_logger(appLogger);
spdlog::flush_on(spdlog::level::debug);    
appLogger->warn("this should appear in both console and file");

Do you happen to have a debugger attached when running the program? — Jaa-c, Sep 12 '18 at 12:07
I ran with debugger and also without debugger, both does not output the spdlogging. — Main, Sep 12 '18 at 12:08
Do you have any other debuggers/IDEs running? Perhaps the platform debug output (Windows has one) can only be consumed by one receiver? — Kuba hasn't forgotten Monica, Sep 12 '18 at 12:29

score 1 · Accepted Answer · answered Sep 13 '18 at 06:51

Yes, the application output does not output the spdlogs. But, I manage to output to terminal by following steps.

Go to Projects, then choose Run configuration for selected kit
In run settings, check the "Run in terminal" option
Next, add console to CONFIG in Project pro file
Clean the project
Build and run.

If these steps don't help, you can delete entire build directory and run the steps again.

score 1 · Answer 2 · answered Oct 11 '18 at 19:03

I had the same issue, and only way I could get the log messages to appear in the application output tab was to use the msvc logger.

auto sink   = std::make_shared<spdlog::sinks::msvc_sink_mt>();
auto logger = std::make_shared<spdlog::logger>("msvc_logger", sink);

The flip side of this logger is that it doesn't print to the console/terminal.

To write to both the application output and the console using the same logger you could create a distributed sink as this:

auto console_sink = std::make_shared<spdlog::sinks::stdout_color_sink_mt>();
auto msvc_sink    = std::make_shared<spdlog::sinks::msvc_sink_mt>();
auto dist_sink    = std::make_shared<spdlog::sinks::dist_sink_st>();
dist_sink->add_sink(msvc_sink);
dist_sink->add_sink(console_sink);
auto logger = std::make_shared<spdlog::logger>("multi_sink", dist_sink)
logger->info("testing multiple sinks");

Why Qt Creator's application output does not print from spdlog logger

2 Answers2