Mail Archives: djgpp/1996/04/15/02:04:15
On 14 Apr 1996, Paul Derbyshire wrote:
> In DJGPP 2.0, the 0xD0000000 address for video memory was removed. This
> will break virtually all my already written programs, requiring me to
> rewrite all their video functions to use the slower libgr that routines,
> and requiring me to completely rewrite programs that use a blitting
> function I wrote.
V2.0 offers several options to deal with this. The fastest (if a bit
dangerous) is the so-called `nearptr' facility that essentially lets you
write to any absolute memory address; that is the feature you were
(ab)using in v1.x. It is a bit dangerous because it effectively disables
memory protection for the window of time that you use that direct access,
so a buggy program can destroy everything on your machine.
There are other options, a bit more slow, all of them described in the v2
FAQ (v2/faq200b.zip from the same place you intend to get v2), which see.
> Is there any way to upgrade and preserve backward compatibility for these
> programs? (In fact it seems rather irresponsible, at least in hindsight,
> to make a feature on a program only to remove it later such that people
It seems to me rather irresponsible to make such inferences without as
much as waiting for your question to be answered. At least you could read
the FAQ for v2, I'm sure it won't leave many of your questions unanswered.
> have to rewrite lots of stuff... Was it known in advance when you made the
> D0000000 thing that it wasn't permanent, as my docs never said not to use
> it...?)
Does your docs include the FAQ for v1.x? The latest version of that FAQ
(faq102.zip from the same place you get DJGPP v1.x) explicitly tells you
in section 18.9 that this feature will disappear in v2.0.
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