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Date:	Fri, 26 Jul 2013 04:14:17 -0700 (PDT)
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Subject:	Re: Beta Test: CWSDPMI r7 - 4GB support
From:	Georg Potthast <dosusb AT googlemail DOT com>
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Thank you very much for the information. I did not know about these functions and will try that.

Georg

Am Freitag, 26. Juli 2013 02:04:22 UTC+2 schrieb Charles Sandmann:
> >"Georg Potthast" <dosusb AT googlemail DOT com> wrote in message 
> 
> >news:788e2b72-ab43-4ae4-8401-97db486d2615 AT googlegroups DOT com...
> 
> >I have a question which I do not know if this related to CWSDPMI. I develop 
> 
> >my programs in a Windows XP DOS box and they >work fine there. When I then 
> 
> >try them in real mode DOS they crash due to uninitialized pointers. So I 
> 
> >have to work through the >program again and fix that. But some of these 
> 
> >problems I may not find and my users observe crashes.
> 
> 
> 
> >Does Windows DPMI set the allocated memory to zero for you while CWSDPMI 
> 
> >does not? Then a "char* mystring;" is set to >NULL by Windows.
> 
> 
> 
> CWSDPMI does not initialize the memory (to improve performance).  On a 
> 
> single process system, there is no need to do this if the program is 
> 
> properly written (no security issues leaking data).
> 
> 
> 
> To find these pointers (or to simply fix it), DJGPP has two features which 
> 
> allow you to fill the memory, see crt0.h:
> 
> 
> 
> /* If set, fill sbrk()'d memory with a constant value.  If not, memory
> 
> ** gets whatever happens to have been in there, which breaks some
> 
> ** applications. */
> 
> #define _CRT0_FLAG_FILL_SBRK_MEMORY             0x0020
> 
> 
> 
> /* If set, fill memory (above) with 0xdeadbeef, else fill with zero.
> 
> ** This is especially useful for debugging uninitialized memory problems. */
> 
> #define _CRT0_FLAG_FILL_DEADBEEF                0x0040

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