hi,

yesbird wrote:
> Greetings !
>
> I am trying to build official beta from this tarball:
> povunix-v3.8.0-beta.2-src.tar.gz.
>
> Build is successful, but on runtime I am getting following error:
> Illegal instruction (core dumped).
>
> I guess that by default 'configure' turns on support for modern
> instructions, that my CPU is not supported, so what is the best way
> to control them and avoid this error ?
>
> My present environment is following:
> Intel(R) Core(TM) i5 CPU  750  @ 2.67GHz
> Ubuntu 24.04.3 LTS
> --
> YB

I published build scripts once or twice, see link.  write if further problems.
<news.povray.org/web.660c3b34a01057ea1686e436cde94f1%40news.povray.org>


regards, jr.

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On 08/11/2025 10:11, jr wrote:
> I published build scripts once or twice, see link.  write if further problems.
> <news.povray.org/web.660c3b34a01057ea1686e436cde94f1%40news.povray.org>

Thanks, jr, for the fast reply, I will try it, but this solution looks
like, a hack. I'd prefer 'official' method to control usage of advanced
CPU instructions, via config parameters.

Don't you know, if it's possible ?
-- 
YB

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yesbird wrote:
> ...
> Thanks, jr, for the fast reply, I will try it, but this solution looks
> like, a hack.

well, it is for WFP's "yuqk" fork :-).


> I'd prefer 'official' method to control usage of advanced
> CPU instructions, via config parameters.
> Don't you know, if it's possible ?

unsure even what you mean.  there are some bits of the source which are
"hand-optimised" for specific CPU types, but the detection & inclusion is
automatic.

either way, I've attached another "hack"[*] </grin>, a beta.2 build script.

[*] anyway, works.  </shrug>


regards, jr.

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Attachments:
Download 'povray.slackbuild.txt' (1 KB)

On 08/11/2025 12:32, jr wrote:
> unsure even what you mean.  there are some bits of the source which are
> "hand-optimised" for specific CPU types, but the detection & inclusion is
> automatic.
> 
> either way, I've attached another "hack"[*] </grin>, a beta.2 build script.
> 
> [*] anyway, works.  </shrug>


Unfortunately results is the same: "no result".
---------------------------------------------------------------------
./unix/povray +i./scenes/advanced/biscuit.pov -f +d +p +v +w320 +h240 
+a0.3 +L./include
make: *** [Makefile:1089: check] Illegal instruction (core dumped)
---------------------------------------------------------------------
YB

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On 11/8/25 02:55, yesbird wrote:
> On 08/11/2025 12:32, jr wrote:
>> unsure even what you mean.  there are some bits of the source which are
>> "hand-optimised" for specific CPU types, but the detection & inclusion is
>> automatic.
>>
>> either way, I've attached another "hack"[*] </grin>, a beta.2 build 
>> script.
>>
>> [*] anyway, works.  </shrug>
> 
> 
> Unfortunately results is the same: "no result".
> ---------------------------------------------------------------------
> ./unix/povray +i./scenes/advanced/biscuit.pov -f +d +p +v +w320 +h240 
> +a0.3 +L./include
> make: *** [Makefile:1089: check] Illegal instruction (core dumped)
> ---------------------------------------------------------------------
> YB
> 

There can be many causes for what you are seeing. Things you might try:

1) Download the latest yuqk tarball at:

https://news.povray.org/povray.binaries.programming/thread/%3C67eba626%40news.povray.org%3E/

Unpack it and run:

./configure -q COMPILED_BY="YB_yuqk" CXXFLAGS="-std=c++17"
make -j4
make check

The yuqk fork ships without any compiler optimizations during 
./configure - aside from the cpu specific noise code where it has fixed 
some 'gnu compiler broken' cpu detection code.

2) Both the default unix build and the build script jr provided use 
-ffast-math. There are a number of flaky fails due recent compiler 
changes to what -ffast-math does. Change that flag to: -fno-fast-math or 
add the flag -fno-finite-math-only to your CXXFLAGS and try another build.

3) You can try a configure with the defines:

-DDISABLE_OPTIMIZED_NOISE_AVXFMA4 -DDISABLE_OPTIMIZED_NOISE_AVX2FMA3 
-DISABLE_OPTIMIZED_NOISE_AVX

Which 'should' turn off any use of the cpu target specific hand 
optimized code - but they might not turn off the dynamic cpu detection 
code which runs ahead of the hand optimized code (I don't remember).

There is too a -DDISABLE_OPTIMIZED_NOISE_AVX_PORTABLE, but my memory is 
fuzzy as to what that means - probably harmless to add it to those above.

4) At a terminal after a illegal instruction problem build, are you able 
to run:

./unix/povray --help

If so, try each of:

touch bogus.pov; ./unix/povray bogus.pov -d +p

touch bogus.pov; ./unix/povray bogus.pov -d -p

touch bogus.pov; ./unix/povray bogus.pov -d +p -fn

Bill P.

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On 08/11/2025 14:59, William F Pokorny wrote:
> There can be many causes for what you are seeing. Things you might try:
> ... 

Many thanks for such a detailed response, I will put these tips to my
'internal storage' ).

The .configure option that helps was '-disable-optimiz'.
Probably I was too lazy to run:
./configure --help

and examine output, instead of disturbing the community, sorry for
inconvenience.
-- 
YB

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hi,

William F Pokorny <ano### [at] anonymousorg> wrote:
> ...
> 2) Both the default unix build and the build script jr provided use
> -ffast-math. There are a number of flaky fails due recent compiler
> changes to what -ffast-math does. Change that flag to: -fno-fast-math or
> add the flag -fno-finite-math-only to your CXXFLAGS and try another build.

thanks !


@yesbird
> The .configure option that helps was '-disable-optimiz'.

good that you found a work-around.


regards, jr.

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On 08/11/2025 16:58, jr wrote:
> good that you found a work-around.

Yes, I did with the help of the community, but don't you think that
it would be better to turn off this optimization by default to
preserve other users from similar issues in future ?
--
YB

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hi,

William F Pokorny <ano### [at] anonymousorg> wrote:
> ...
> 2) Both the default unix build and the build script jr provided use
> -ffast-math. There are a number of flaky fails due recent compiler
> changes to what -ffast-math does. Change that flag to: -fno-fast-math or
> add the flag -fno-finite-math-only to your CXXFLAGS and try another build.

in light of yesbird asking whether optimisation should be turned off perhaps, I
think it would be beneficial if (at least) the build flags for default *NIX were
appended / updated to include the '-fno-finite-math-only'.  can do ?


regards, jr.

Post a reply to this message

On 11/10/25 04:52, jr wrote:
> hi,
> 
> William F Pokorny <ano### [at] anonymousorg> wrote:
>> ...
>> 2) Both the default unix build and the build script jr provided use
>> -ffast-math. There are a number of flaky fails due recent compiler
>> changes to what -ffast-math does. Change that flag to: -fno-fast-math or
>> add the flag -fno-finite-math-only to your CXXFLAGS and try another build.
> 
> in light of yesbird asking whether optimisation should be turned off perhaps, I
> think it would be beneficial if (at least) the build flags for default *NIX were
> appended / updated to include the '-fno-finite-math-only'.  can do ?
> 

No(*), not easily.

---

It's true I did some github things a year or so ago to get bumped to a 
developer with the idea I might do a few quick commits like this, but my 
github upgrade from contributor to developer didn't go well. Best I 
could tell, I ended up with developer permission to one hidden / 
developer only fork / branch about which I know nothing.

None of the automated, github, build, check and release stuff is 
currently working. I never understood that set up beyond checking 
results of the auto-build-check fails. I have now not used github 
itself, except for occasionally commenting on issues posted there, for 
more than 5 years.

I cannot help with or support any windows specific development.

The suggested change should be made in at least 3 github branches. The 
github support infrastructure is really nice when it's all working - but 
even then, the simplest change takes non-trivial 'git / github' time.

---

My Unix/Linux only yuqk fork is different. The Unix build system itself 
is substantially different. I don't even have the --disable-optimiz 
configure option YB used(**) to build on his machine, for example.

---

Lastly, of late, real life is leaving me with much less time for my 
POV-Ray hobby :-(.

Bill P.


(*) - You're likely guessing correctly that YB's core issue comes down 
to the -ffast-math changes. The --disable-optimize option almost 
certainly turns off fast math.

(**) - Completely non-optimized POV-Ray builds are slow. (Though, it is 
a workaround for the gnu compiler optimizations breaking the dynamic cpu 
detection code issue (fixed in yuqk no matter the compiler optimization 
level))

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