[linrad] Re: Memory leakage.

[Leif Asbrink <sm5bsz.com; leif@xxxxxxxxxxxxxxxx>]

Hi Richard,

> I cant speak as an accomplished programmer, having only done simple 
> projects in C++
> Still the code seems to be part of a routine. It looks like
> 
>  cross_cursor is an object of class XCreateFontCursor
Yes. XCreateFontCursor allocates memory to a pointer but
XFreeCursor frees the memory again.

If I omit XFreeCursor, valgrind reports some still reachable
leakage but the number of definitely lost memory stays the same.

> Maybe this is not being destroyed after use?
> 
> I havent the faintest how you would find the class code for this
> X11 on my machine appears to be all C, though I cant locate 
> source - I have just loaded Mandrake from a CD 
I do not understand what "the class code for this" means. 
Not at all being a programmer I become confused.

When reading about C++ (which I find alien and impractical)
I get the impression that Class is simply a data structure,
a list of variables that could contain data or pointers
to data, pointers or routines.

It seems to me that XCreateFontCursor does not only allocate
memory to cross_cursor which I can free with XFreeCursor,
it must also allocate something else - maybe routines needed
by the pointers to routines in the list of pointers constituting
the data of cross_cursor. My problem is that I can not find out
whether I should call some XCloseCursorThings (or whatever) after
having freed the last cursor. Finding XFreeCursor was not
a trivial thing. One would expect the man page about 
XCreateFontCursor to give a hint - but it does not:-(

I was hoping someone could tell me proper name of 
XCloseCursorThings if something like that exists - or
tell me that the code below is perfectly correct and complete
and that I should disregard the valgrind output.

73

Leif / SM5BSZ





> 
> No doubt there are more accomplished programmers who could advise..
> 
> Richard
> 
> 
> Leif Asbrink wrote:
> 
> >Hello Richard,
> >
> >  
> >
> >>Lost memory is allocated when an object in C++ is created , but not 
> >>released when the object is destroyed. This is usually performed by the 
> >>destructor for the class if the class has been written properly.
> >>    
> >>
> >???????????????
> >I have seen similar text before, but it does not tell me anything
> >at all. I have for example this problem. Only four simple statements:
> >
> >xdis = XOpenDisplay(":0");
> >cross_cursor = XCreateFontCursor(xdis, XC_diamond_cross);
> >XFreeCursor(xdis, cross_cursor);
> >XCloseDisplay(xdis);
> >return 0;
> >
> >If I comment out the second and the third statement all is ok,
> >but with both of them in place I get this report from valgrind:
> >==9031== LEAK SUMMARY:
> >==9031==    definitely lost: 8 bytes in 1 blocks.
> >==9031==    indirectly lost: 104 bytes in 4 blocks.
> >
> >  
> >
> >>This results in increasing useless RAM utilization and eventually disk 
> >>swapping, slowing everything down.
> >>    
> >>
> >How can I detect whether it happened? 
> >
> >  
> >
> >>(hope I am not telling you things you already know.. :)  )
> >>    
> >>
> >You told things I kind of heard about but that I do not
> >understand how to deal with. Did I make a mistake in the
> >example above or is X11 not quite ok yet? Do you know?
> >Using pthreads is much worse..............
> >
> >73
> >
> >Leif
> >
> >
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