winfave@dutrun2.tudelft.nl (Alexander Verbraeck) (05/16/91)
I have a very strange problem using the EXEC-procedure under
Turbo Pascal 5.0. The problem is that the computer locks sometimes
when executing the Exec-call. At first, the problem occurred when
using an Exec after a heap-compress, and I thought the problem was
with the heap-compression procedure, and not with the Exec-call.
I could, however, reproduce part of the error with a very small
Turbo Pascal program that does not compress the heap.
The program is as follows (and YES, I KNOW it should not run!)
------------------------------------------------------------------------
program testmswp;
{$M $4000,0,655360}
uses Crt, Dos;
procedure ItemFileEdit;
var
DosErrorCode : word;
begin
SwapVectors;
Exec(GetEnv('COMSPEC'),'/C MS-WP.EXE item.txt');
SwapVectors; { The above ^ program does not exist. No problem }
if DosError<>0 then
writeln('EXEC ERROR NUMBER ',DosError);
end;
begin
ItemFileEdit;
end.
------------------------------------------------------------------------
The program does not have enough memory to execute, and therefore a
DosError=8 should occur. This happens in most cases. When I run this
program from a directory with a pathname longer than 20 characters,
the computer locks up, violates CMOS Setup memory, and does other
strange things. So:
C:\TEST> testmsw2 [Enter] works fine, but
C:\TESTTEST.TST\TESTTEST.TST> testmswp [Enter] locks up the computer...
I am not sure it behaves this way on ALL types of computers and versions
of MSDOS. I tested it on three different types of AT and 386 computers,
running MSDOS 4.01, 3.1 and 3.3. It behaved in the same strange way on
ALL three computers. But: not always, not from the IDE, but always from
a "clean" dos version.
When running it under the Turbo Debugger, the problem does NOT occur.
When running it under TD386, the debugger locks after performing the
Exec. I also got an 'Exception 12, Error 0' once.
When loading one or two extra versions of COMMAND.COM, the problem does not
occur, so I think it only happens using the primary copy of MSDOS, which
is the one that was loaded during the boot process.
HELP! Does anyone know what is happening? The program should generate a
DosError=8, independent from the directory it was called from!
Any ideas or pointers to a solution are appreciated!
Sincerely,
-------------------------------------------------------------------------
Alexander Verbraeck e-mail: winfave@duticai.tudelft.nl
Delft University of Technology winfave@hdetud1.bitnet
Department of Information Systems winfave@duticai.uucp
PO Box 356, 2600 AJ The Netherlands winfave@dutrun.tudelft.nl
Tel: +31 15 783805 Fax: +31 15 786632/787022 winfave@dutrun.uucp
-------------------------------------------------------------------------