Re: Pascal Calling Convention

["Randy Brukardt" <randy@rrsoftware.com>]

"Robert A Duff" <bobduff@shell01.TheWorld.com> wrote in message 
news:wccsju4i6f2.fsf@shell01.TheWorld.com...
> tmoran@acm.org writes:
>
>>    What does software/hardware Data Excecution Prevention do on Vista 
>> etc?
>
> I believe DEP causes the operating system to set per-page protections so
> data is not executable, by default.  The checks are done in hardware.
> And of course code pages are not writeable by default.  A process can
> request other page protections.  Requires newer versions of x86.

Right. This moves the permissions from the segments (where Intel had put 
them) to the page table, because OS writers didn't want to take advantage of 
the possibilities of segments. (We wouldn't need 64-bit OSes, with all of 
their incompatibilities, anywhere near as soon had the OSes used segments in 
the first place.)

The two approaches are equivalent, except for the irrational fears of 
certain developers. The effect was to make the X86 much less safe that it 
could have been.

>> (Other than generate spurious errors.)
>
> We eliminated almost all trampolines from GNAT, so newer versions
> won't cause such spurious errors.

Glad to hear it. I turned on DEP on my machine, since I knew that Janus/Ada 
couldn't cause problems with it (and if it did, I wanted to fix them). But I 
couldn't run GNAT very successfully, so I had to turn it back off.

                       Randy.