QB64.org Forum
Active Forums => QB64 Discussion => Topic started by: 40wattstudio on March 03, 2020, 09:36:41 pm
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I've been using _Loadimage quite a bit and from reading the Wiki it sounds like one should preferably use it in conjunction with _Freeimage to prevent memory errors.
_Freeimage seems pretty easy to implement, but how does one test to see that it's actually working?
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Easiest way is just to watch memory usage in Task Manager for your program. Without it, you’ll have a memory leak and resources will increase endlessly until your program crashes. (Depending on program flow, of course. Loading an image once without freeing it won’t crash a program, but to load an image inside a loop repeatedly, definitely will.)
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Ok that sounds pretty simple. Is there a way to monitor it in-program as well, like by printing to the screen a list of loaded and freed images?
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Ok that sounds pretty simple. Is there a way to monitor it in-program as well, like by printing to the screen a list of loaded and freed images?
You might be able to monitor the image handles. Every image has an unique handle which we use to reference it in memory (Handle = _LOADIMAGE(...stuff)).
I *believe* that the first image handle usually starts around -11 and increases by -1 for each image loaded after that. (I’m not at my PC currently, so I can’t test to be certain.)
So load one image, it’s handle value is usually -11. The next image handle value is -12. Then -13....
Free an image and those handles should be recycled when you load a new one.
First image loaded has a handle of -11. Second is -12. Third is -13....
Now, FREE the second image from memory (-12), LOAD a new image, and it *should* recycle that freed handle and have a value of -12...
So let’s say I’m loading up to 10 images in memory. IF I’m loading and freeing them properly, as simple check of something like this would make an easy warning:
SUB ValidateHandle (Handle AS LONG)
IF Handle < -100 THEN
CLS
PRINT “IMAGE MEMORY LEAK IN PROCESS!!”
END
END IF
END SUB
An endless loading and unloading of images would generate more than -100 handles, trip the IF, and report itself as an error for you.
**At least, I think it should work. As I said above, I’m not at the PC currently for 100% testing.