GTK+ Forums

jasonkb · Posted: Sat Apr 21, 2007 11:18 am Post subject: g_print versus printf

Was wondering why printf() will not work until the application shuts down, but g_print() will work anytime? Is there something in GTK+ that blocks console output? Does GTK+ block any other C standard library functions or block any UNIX standards?

I tried to contrust a directory and set user permissions from the C program using libs from <sys/stat.h> and that worked fine during the app. So why does printf() not work?

PS- I'm not annoyed at this, it's mainly a question out of curiosity because similar things happen in other GUI toolkits for C++ like wx or Qt. THere seems to be something in the architecture that I find interesting and wanted to know why. (I'm a Java developer and got used to System.out.println to debug apps)

Interested for replies by anyone!

Regards- Jason
(native language noob)

openldev · Posted: Sat Apr 21, 2007 2:42 pm Post subject:

You are right; GLib does block printf() from executing until the end of your application. This is due to how the main loop works. GLib provides a number of message logging functions such as g_print, g_message, g_critical, and g_warning. g_printf is also provided if you include <glib/gstdio.h>. It all comes down to the main loop function, which blocks printf because of how it is designed. However, if you are designing a GTK+ application, you can just use GLib's message functions.

jasonkb · Posted: Sat Apr 21, 2007 3:49 pm Post subject:

Thankyou very much for explaining this to me. I feel much happier now I know what was causing that behaviour.

I noticed you had placed a <glib/gstdio.h> include statement. That suggests that the normal stdio.h is affected by the event loop. Does this mean that scanf etc will not work? Are there any other C standards affected by this? More importantly will this affect the standard Unix system calls?

Sorry for asking so many questions as I am a complete stranger to native language programming.

Final question: will this event loop prevent me from using 3rd party libraries for C/C++? I was hoping to use sound libraries and xml libraries but if nothing executes untill the program terminates the event loop...

It looks as though I will have much experimenting to do! I must say though I like the simplicity of the GTK+ API. Seems very structured when using it in conjuction with C making it nice and simple to follow the program state. Warrants giving it a good try.

thanks again.

Jason.

openldev · Posted: Sat Apr 21, 2007 11:18 pm Post subject:

As to your stdio.h question, it really all depends on the function. Generally, when using GTK+, you should use the GLib wrapper functions if available because they are cross-platform.

The loop affects standard output, but you are fine beyond that. I haven't found any external libraries that have been affected by this. You should be fine using most libraries.

jasonkb · Posted: Sun Apr 22, 2007 4:37 am Post subject:

Thanks very much for your assistance!!!

Regards,
Jason.