Cannot see debug messages in a unix environment

[KShots]

Does your program actually do what it is supposed to? It looks like it just exits.

Yeah, it does. It spawns a gui, connects to a remote server, and if I run it in a console, it tells me all about the various stages it's going through with the network traffic. When run in Qt-Creator, the above is all I get (with the application itself running).

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Added after 4 minutes:

One reason I can think of is that the new Qt detected your system is using journald for logging and directed the output there.
You can force logging to the console by setting QT_LOGGING_TO_CONSOLE=1, e.g. in the project's run environment.

Cheers,
_

I had almost forgotten about that. I built it from the gentoo ebuild, which may or may not have redirected the log to journald (I do run systemd). That appears to have resolved it, though. Thanks!

[EDIT]

I'm rather confused why this worked. Why am I getting output in my consoles without the environment variable? I was under the impression that nothing would hit stdout/stderr if journald was used, yet I have messages in my console. Am I misunderstanding how the journald interface works?

[JasonC]

I'm rather confused why this worked. Why am I getting output in my consoles without the environment variable? I was under the impression that nothing would hit stdout/stderr if journald was used, yet I have messages in my console. Am I misunderstanding how the journald interface works?

When QT_LOGGING_TO_CONSOLE is not specified, Qt essentially tries to guess if you're running in a terminal or not to determine where to send the logs. Terminal = stderr, anything else = whatever your Qt installation is configured to support (e.g. journald).

Afaict, this behavior was introduced in Qt 5.4. See https://codereview.qt-project.org/#/c/89357/, in particular:

This commit adds logic similar to Windows's: if the application has a controlling TTY, we'll use stderr. Otherwise, we'll use the system log. This is technically a change in behavior: previously, we would always use the system log, unless the environment variable told us not to.

The environment variable can always be specified to force one or the other, but if it's not specified, a choice is made automatically.

For more information see:
http://lists.qt-project.org/pipermai...ly/017588.html (discussion with some rationale for above change)
http://stackoverflow.com/questions/2...-default-on-qt (a mostly good summary)