[Gambas-user] Crash with Free()

[Demosthenes Koptsis]

:) Pointers are tricky!
And may be this subject is difficult for BASIC programmers like me.
But in time we can learn their tricks and pay attention to such cases.

In my book i simulate and describe such cases based on
http://www.yolinux.com/TUTORIALS/C++MemoryCorruptionAndMemoryLeaks.html

i do not make exact port of the C code to Gambas3 and i know that it
cannot be done but i can make some remarks for the usage of pointers and
common mistakes.

Jussi you can also use this page to write code for your Tester.
For example this crash you saw was

"Freeing memory that was not allocated."

 

On Thu, 2011-01-13 at 22:07 +0200, Jussi Lahtinen wrote:
> Aaaa... of course, pointer is not correct to free after "pp += 4".
> Though, result shouldn't be signal 11.
> 
> Jussi
> 
> 
> 2011/1/13 Benoît Minisini <gambas at ...1...>
> 
> > > Hi!
> > > I was adding some test for pointer arithmetic when noticing this.
> > > GambasTester will pass, but when you close main form, signal 11 will
> > rise.
> > > Commenting out Free(pp) from mTest: line 1070, will prevent crash.
> > >
> > > Gambas 3 rev 3452 @ Ubuntu 10.10 64bit
> > >
> > > Jussi
> >
> > You are calling Free(pp) whereas pp is not the pointer returned by Alloc()
> > anymore. So you get a crash...
> >
> > --
> > Benoît Minisini
> >
> >
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-- 
Regards,
Demosthenes