Bug#891682: [Pkg-pascal-devel] Bug#891682: castle-game-engine: FTBFS on arm64: assorted test suite errors and failures

[Punit Agrawal]

block 891682 by 895693

On Sat, Apr 14, 2018 at 7:29 PM, Paul Gevers  wrote:
> Hi Punit,
>
> Thanks for your work.
>
> On 14-04-18 19:25, Punit Agrawal wrote:
>> I'll file a bug against the debian fpc package. What would be the best
>> way to bring this to upstream's attention?
>
> Upstream bug tracker lives here:
> https://bugs.freepascal.org/my_view_page.php

Thanks for the pointer.

Bugs filed both in debian[0] and upstream[0].

[0] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=895693
[1] https://bugs.freepascal.org/view.php?id=33607

Bug#891682: [Pkg-pascal-devel] Bug#891682: castle-game-engine: FTBFS on arm64: assorted test suite errors and failures

[Paul Gevers]

Hi Punit,

Thanks for your work.

On 14-04-18 19:25, Punit Agrawal wrote:
> I'll file a bug against the debian fpc package. What would be the best
> way to bring this to upstream's attention?

Upstream bug tracker lives here:
https://bugs.freepascal.org/my_view_page.php

Paul



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Bug#891682: [Pkg-pascal-devel] Bug#891682: castle-game-engine: FTBFS on arm64: assorted test suite errors and failures

[Punit Agrawal]

On Sat, Apr 14, 2018 at 1:56 PM, Michalis Kamburelis
 wrote:
>  2018-04-14 12:42 GMT+02:00 Punit Agrawal :
>> At this point, I suspect it's a compiler issue. I've created a
>> reproducer (attached) that highlights the problem and behaves
>> differently on arm64 and x86.
>>
>> Note: I am not at all familiar with Pascal. Input from somebody more
>> familiar with the language ecosystem will be greatly appreciated.
>>
>
> Great job!
>
> Note that in your testcase, the minimized "TRectangle.ScaleAround0"
> does not set Result.Width, Result.Left in some cases. And, since this
> is a record, the uninitialized fields are undefined (may contain
> memory garbage).
>
> It should not matter for the result (from what I see, the
> TRectangle.Width is always guaranteed to be 0 when calling this). But
> maybe writing something like
>
> """
>if Width <= 0 then
>begin
>   Result.Width  := Width;
>   Result.Left   := Left;
>end else
>   Writeln('This should never happen');
> """
>
> would make this clearer?

I updated the reproducer as you suggested. The behaviour is unchanged as below.

>
> The testcase definitely makes sense to me, and if you get different
> results on different CPUs -- then indeed we have nicely reproducible
> FPC bug.

The output on arm64

arm64:~/src/fpc-test$ ./test
S.Width=0 R.ScaleAround0(2).Width=214748364800

and on x86-64

x86-64$ ./test
S.Width=0 R.ScaleAround0(2).Width=0

I'll file a bug against the debian fpc package. What would be the best
way to bring this to upstream's attention?

>
> (P.S. I'm the castle-game-engine upstream author.)

Cool! Thanks a lot for looking over the findings. Very much appreciated.


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Bug#891682: [Pkg-pascal-devel] Bug#891682: castle-game-engine: FTBFS on arm64: assorted test suite errors and failures

[Michalis Kamburelis]

 2018-04-14 12:42 GMT+02:00 Punit Agrawal :
> At this point, I suspect it's a compiler issue. I've created a
> reproducer (attached) that highlights the problem and behaves
> differently on arm64 and x86.
>
> Note: I am not at all familiar with Pascal. Input from somebody more
> familiar with the language ecosystem will be greatly appreciated.
>

Great job!

Note that in your testcase, the minimized "TRectangle.ScaleAround0"
does not set Result.Width, Result.Left in some cases. And, since this
is a record, the uninitialized fields are undefined (may contain
memory garbage).

It should not matter for the result (from what I see, the
TRectangle.Width is always guaranteed to be 0 when calling this). But
maybe writing something like

"""
   if Width <= 0 then
   begin
  Result.Width  := Width;
  Result.Left   := Left;
   end else
  Writeln('This should never happen');
"""

would make this clearer?

The testcase definitely makes sense to me, and if you get different
results on different CPUs -- then indeed we have nicely reproducible
FPC bug.

(P.S. I'm the castle-game-engine upstream author.)
Regards,
Michalis