FPC 3.3.1 Error 216 General Protection fault for abs with GO32V2 /
SSE2
lazarus / 64-FPC development

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Gammatester · 2018-12-01 19:48

There is a problem with the abs function for FPC3.3.1/GO32V2 when
using SSE2. FPC was installed from
go32v2-fpc-3.3.1.x86_64-linux.tar.gz. The following program
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i program
t_abssse;var  x: double;begin  writeln('Abs bug with SSE/GO32V2');  x
:= -1;  writeln('x=',x);  writeln('sin(x)=',sin(x)); 
writeln('abs(x)=',abs(x));end. works as expected under Window XP and
Windows 8 without SSE and throws a runtime error 216 when compiled
with  -CfSSE2.  Should this be reported as an issue in the bugtracker?
Code: [Select]Windows XP

D:\FPC331D\bin\go32v2>fpc
Free Pascal Compiler version 3.3.1-r20:40421 [2018/11/30] for i386
Copyright (c) 1993-2018 by Florian Klaempfl and others

D:\FPC331D\bin\go32v2>ver
Microsoft Windows XP [Version 5.1.2600]

D:\FPC331D\bin\go32v2>fpc.exe t_abssse.pas

D:\FPC331D\bin\go32v2>t_abssse.exe
Abs bug with SSE/GO32V2
x=-1.0000000000000000E+000
sin(x)=-8.41470984807896506665E-0001
abs(x)= 1.0000000000000000E+000

D:\FPC331D\bin\go32v2>fpc -CfSSE2 t_abssse.pas

D:\FPC331D\bin\go32v2>t_abssse.exe
Abs bug with SSE/GO32V2
x=-1.0000000000000000E+000
sin(x)=-8.41470984807896506665E-0001
Runtime error 216 at $000018B2
  $000018B2
  $00001795

abs(x)=
D:\FPC331D\bin\go32v2>

Windows 8

C:\FPC331D\bin\go32v2>fpc.exe
Free Pascal Compiler version 3.3.1-r20:40421 [2018/11/30] for i386
Copyright (c) 1993-2018 by Florian Klaempfl and others

C:\FPC331D\bin\go32v2>ver
Microsoft Windows [Version 6.2.8400]

C:\FPC331D\bin\go32v2>fpc t_abssse.pas

C:\FPC331D\bin\go32v2>t_abssse.exe
Abs bug with SSE/GO32V2
x=-1.0000000000000000E+000
sin(x)=-8.41470984807896506665E-0001
abs(x)= 1.0000000000000000E+000

C:\FPC331D\bin\go32v2>fpc -CfSSE2 t_abssse.pas

C:\FPC331D\bin\go32v2>t_abssse.exe
Abs bug with SSE/GO32V2
x=-1.0000000000000000E+000
sin(x)=-8.41470984807896506665E-0001
Runtime error 216 at $000018B2
  $000018B2
  $00001795

abs(x)=
C:\FPC331D\bin\go32v2>

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lucamar · 2018-12-01 20:32

Have you tried in an actual DOS box? It may be a strange interaction
between the extender and the OS treatment of the FPU.

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Gammatester · 2018-12-01 21:06

Quote from: lucamar on December 01, 2018, 09:32:42 pmHave you tried in
an actual DOS box? It may be a strange interaction between the
extender and the OS treatment of the FPU.
This makes no difference, here the results for Windows 98 and DOSBox
(the first runs are without SSE the second with SSE):
Code: [Select]C:\TMP>ver
Windows 98 [Version 4.10.1998]

C:\TMP>t_abs.exe
Abs bug with SSE/GO32V2
x=-1.0000000000000000E+000
sin(x)=-8.41470984807896506665E-0001
abs(x)= 1.0000000000000000E+000

C:\TMP>T_ABSSSE.EXE
Abs bug with SSE/GO32V2
x=-1.0000000000000000E+000
sin(x)=-8.41470984807896506665E-0001
Runtime error 216 at $000018B2
  $000018B2
  $00001795

abs(x)=
C:\TMP>

DOSBox version 0.74-2. Reported DOS version 5.00.
Abs bug with SSE/GO32V2
x=-1.0000000000000000E+000
sin(x)=-8.41470984807896506665E-0001
abs(x)= 1.0000000000000000E+000

Abs bug with SSE/GO32V2
x=-1.0000000000000000E+000
sin(x)=-8.41470984807896506665E-0001
abs(x)=
Error and error addr only displayed on screen, could not be redirected
with DOSBox

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lucamar · 2018-12-01 21:58

Sorry, by "DOS box" I meant a computer with a real DOS (as in MS-DOS,
DR-DOS, FreeDOS, ...) in it, not the emulator  But Windows 98 (boot-up
with no GUI, I hope?) is enough test.

I kinfd of remember there was some problem with the FPU control word
but I haven't been able to find the reference, sorry again.

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Gammatester · 2018-12-01 22:22

Quote from: lucamar on December 01, 2018, 10:58:54 pmSorry, by "DOS
box" I meant a computer with a real DOS (as in MS-DOS, DR-DOS,
FreeDOS, ...) in it, not the emulator  But Windows 98 (boot-up with no
GUI, I hope?) is enough test.Again no difference, same output for
Win98 GUI / NoGUI, and the results for
Code: [Select]MS-DOS Version 6.22

Abs bug with SSE/GO32V2
x=-1.0000000000000000E+000
sin(x)=-8.41470984807896506665E-0001
abs(x)= 1.0000000000000000E+000

Abs bug with SSE/GO32V2
x=-1.0000000000000000E+000
sin(x)=-8.41470984807896506665E-0001
abs(x)=
DOS version run from floppy on real hardware (Pentium 4).