problem with output of the program on different OS

[pereges]

I have a C program which I created on Windows machine. I have compiled
and executed the program on windows machine and it gives me the
consistent output every time i run it. for eg.

input a = 2, b =3

lets say a sum operation is to be performed, then:

output: 5

The output is always consistent and correct with regards to input.

I tried to run the program on my linux machine. The program compiles
and executes but I'm getting strange results. For eg. for the problem
of addition above:

input a = 2 b = 3

output: 1

i execute the program again:

input a = 2 b = 3

output: 6

and again:

input a = 2 b= 3

output 0

What is happening ?

[Richard Heathfield]

Re: problem with output of the program on different OS

pereges said:

I have a C program which I created on Windows machine. [...]
>
The output is always consistent and correct with regards to input.
>
I tried to run the program on my linux machine. The program compiles
and executes but I'm getting strange results. [...]
>
What is happening ?

Classic case of undefined behaviour. For a more detailed diagnosis, please
provide source code.

--
Richard Heathfield <http://www.cpax.org.uk >
Email: -http://www. +rjh@
Google users: <http://www.cpax.org.uk/prg/writings/googly.php>
"Usenet is a strange place" - dmr 29 July 1999

[pereges]

Re: problem with output of the program on different OS

On May 8, 1:26 pm, Richard Heathfield <r...@see.sig.i nvalidwrote:
<snip>

Classic case of undefined behaviour. For a more detailed diagnosis, please
provide source code.
>

The code is 650 lines and it is divided in many modules. I don't mind
posting it but most people will resent it.

Do yout think problems like this one can arise by using non standard
compilers like PellesC ?

[Ian Collins]

Re: problem with output of the program on different OS

pereges wrote:

On May 8, 1:26 pm, Richard Heathfield <r...@see.sig.i nvalidwrote:
<snip>

>Classic case of undefined behaviour. For a more detailed diagnosis, please
>provide source code.
>>

>
The code is 650 lines and it is divided in many modules. I don't mind
posting it but most people will resent it.
>
Do yout think problems like this one can arise by using non standard
compilers like PellesC ?
>

More likely undefined behaviour in the code that relies on the
behaviour of the original compiler.

Try and distill a short example that demonstrates the problem.

--
Ian Collins.

[pereges]

Re: problem with output of the program on different OS

On May 8, 1:42 pm, Ian Collins <ian-n...@hotmail.co mwrote:

Do yout think problems like this one can arise by using non standard
compilers like PellesC ?

>
More likely undefined behaviour in the code that relies on the
behaviour of the original compiler.
>
Try and distill a short example that demonstrates the problem.

The original compiler I had used was Pelles C (to get a working
output). I will try to post a small version of my code and describe
where I think the problem lies.

[Richard Heathfield]

Re: problem with output of the program on different OS

pereges said:

On May 8, 1:26 pm, Richard Heathfield <r...@see.sig.i nvalidwrote:
<snip>

>Classic case of undefined behaviour. For a more detailed diagnosis,
>please provide source code.

>
The code is 650 lines and it is divided in many modules. I don't mind
posting it but most people will resent it.

Zip up all the .c and .h files and any data required for reproducing the
problem, stick it on the Web somewhere, and post a URL. That way, anyone
who wants to look can do so, without inconveniencing anyone who doesn't
want to.

Don't include executable images or object files in the zip file; nobody
will use them anyway, so they'd just be a waste of bandwidth.

--
Richard Heathfield <http://www.cpax.org.uk >
Email: -http://www. +rjh@
Google users: <http://www.cpax.org.uk/prg/writings/googly.php>
"Usenet is a strange place" - dmr 29 July 1999

[Nick Keighley]

Re: problem with output of the program on different OS

On 8 May, 09:20, pereges <Brol...@gmail. comwrote:

I have a C program which I created on Windows machine. I have compiled
and executed the program on windows machine and it gives me the
consistent output every time i run it. for eg.
>
input a = 2, b =3
>
lets say a sum operation is to be performed, then:
>
output: 5
>
The output is always consistent and correct with regards to input.
>
I tried to run the program on my linux machine. The program compiles
and executes but I'm getting strange results. For eg. for the problem
of addition above:
>
input a = 2 b = 3
>
output: 1
>
i execute the program again:
>
input a = 2 b = 3
>
output: 6
>
and again:
>
input a = 2 b= 3
>
output 0
>
What is happening ?

there is an instance of Undefined Behaviour on line 42

--
Nick Keighley

[jacob navia]

Re: problem with output of the program on different OS

pereges wrote:

On May 8, 1:26 pm, Richard Heathfield <r...@see.sig.i nvalidwrote:
<snip>

>Classic case of undefined behaviour. For a more detailed diagnosis, please
>provide source code.
>>

>
The code is 650 lines and it is divided in many modules. I don't mind
posting it but most people will resent it.
>
Do yout think problems like this one can arise by using non standard
compilers like PellesC ?
>
>

Pelles C is a very standard compiler (ansic 89), and it is derived from
lcc, that is very strictly conforming to C 89. Do not blame the compiler
unless you are very sure of your code.


--
jacob navia
jacob at jacob point remcomp point fr
logiciels/informatique

http://www.cs.virginia.edu/~lcc-win32

[Bart]

Re: problem with output of the program on different OS

On May 8, 9:20 am, pereges <Brol...@gmail. comwrote:

I have a C program which I created on Windows machine. I have compiled
and executed the program on windows machine and it gives me the
consistent output every time i run it. for eg.
>
input a = 2, b =3
>
lets say a sum operation is to be performed, then:
>
output: 5
>
The output is always consistent and correct with regards to input.
>
I tried to run the program on my linux machine. The program compiles
and executes but I'm getting strange results. For eg. for the problem
of addition above:
>
input a = 2 b = 3
>
output: 1
>
i execute the program again:
>
input a = 2 b = 3
>
output: 6
>
and again:
>
input a = 2 b= 3
>
output 0
>
What is happening ?

Well, you can forget about the Windows version and just try some
debugging! Your program clearly isn't producing the output you expect.

Or, to save some work, compile with something like gcc with every
possible warning. Perhaps like:

gcc -W -Wall -ansi -pedantic -Wformat-nonliteral -Wcast-align -
Wpointer-arith -Wbad-function-cast -Wmissing-prototypes -Wstrict-
prototypes -Wmissing-declarations -Winline -Wundef -Wnested-externs -
Wcast-qual -Wshadow -Wconversion -Wwrite-strings -ffloat-store -fno-
builtin -O2 -g -pg YOURPROG.c

(with thanks to R. Heathfield).

Then it might give some clues as to what might be wrong. Maybe some
array is too small; just double each one. It might help, or it might
also hide the real error.

650 lines isn't very big, why many modules? Sometimes separating into
modules can introduce more errors. Perhaps try temporarily combining
into one big file.

--
Bartc

[pereges]

Re: problem with output of the program on different OS

On May 8, 6:45 pm, Bart <b...@freeuk.co mwrote:

Well, you can forget about the Windows version and just try some
debugging! Your program clearly isn't producing the output you expect.

Can you please tell me about a good debugger ? Is there some
preliminary stuff I should read about debugging in C prior to using a
debugger ?

650 lines isn't very big, why many modules? Sometimes separating into
modules can introduce more errors. Perhaps try temporarily combining
into one big file.

well, I have a total of 9 modules in my program(countin g the .c and
the corresponding .h as 1 module).I was told to write the code in
sucha way that the individual modules can be reused in some other
programs.

[Richard Heathfield]

Re: problem with output of the program on different OS

pereges said:

On May 8, 6:45 pm, Bart <b...@freeuk.co mwrote:
>

>Well, you can forget about the Windows version and just try some
>debugging! Your program clearly isn't producing the output you expect.

>
Can you please tell me about a good debugger ? Is there some
preliminary stuff I should read about debugging in C prior to using a
debugger ?

Debuggers are over-rated by some people, and can be a huge time sink if
used flailingly.

>650 lines isn't very big, why many modules? Sometimes separating into
>modules can introduce more errors. Perhaps try temporarily combining
>into one big file.

>
well, I have a total of 9 modules in my program(countin g the .c and
the corresponding .h as 1 module).I was told to write the code in
sucha way that the individual modules can be reused in some other
programs.

Yes, I agree with you that the comment about design was misguided. Module
boundaries should be drawn to reflect differences in functionality. The
idea that you have some kind of Procrustean source bed, such that any file
longer than N lines must be split, is silly.

Is that zip file ready yet?

--
Richard Heathfield <http://www.cpax.org.uk >
Email: -http://www. +rjh@
Google users: <http://www.cpax.org.uk/prg/writings/googly.php>
"Usenet is a strange place" - dmr 29 July 1999

[pereges]

Re: problem with output of the program on different OS

On May 9, 10:52 am, Richard Heathfield <r...@see.sig.i nvalidwrote:

Debuggers are over-rated by some people, and can be a huge time sink if
used flailingly.

Yes, I agree with you that the comment about design was misguided. Module
boundaries should be drawn to reflect differences in functionality. The
idea that you have some kind of Procrustean source bed, such that any file
longer than N lines must be split, is silly.

Is that zip file ready yet?

http://www.savefile.com/files/1547165

Can you please provide some general tips as to how I can improve my
style of coding ?

thanks

[Richard Heathfield]

Re: problem with output of the program on different OS

pereges said:

On May 9, 10:52 am, Richard Heathfield <r...@see.sig.i nvalidwrote:
>

<snip>

>

>Is that zip file ready yet?

>
http://www.savefile.com/files/1547165

A somewhat cumbersome interface to a somewhat awkward RAR file. Not your
fault, of course - you take the Web space you can get - but I've bundled
up the files as an easily accessible .zip file, which others may find more
convenient:

http://www.cpax.org.uk/scratch/raytrace.zip

Can you please provide some general tips as to how I can improve my
style of coding ?

Yes, but that reply will take some time to write. *This* reply is really
just to facilitate easy access to your code, for the convenience of others
who may want to help you too. I'll get back to you - watch this space.

--
Richard Heathfield <http://www.cpax.org.uk >
Email: -http://www. +rjh@
Google users: <http://www.cpax.org.uk/prg/writings/googly.php>
"Usenet is a strange place" - dmr 29 July 1999

[Spiros Bousbouras]

Re: problem with output of the program on different OS

On 9 May, 07:20, pereges <Brol...@gmail. comwrote:

On May 9, 10:52 am, Richard Heathfield <r...@see.sig.i nvalidwrote:
>

Debuggers are over-rated by some people, and can be a huge time sink if
used flailingly.
Yes, I agree with you that the comment about design was misguided. Module
boundaries should be drawn to reflect differences in functionality. The
idea that you have some kind of Procrustean source bed, such that any file
longer than N lines must be split, is silly.
Is that zip file ready yet?

>
http://www.savefile.com/files/1547165

I've been to the page ; I don't see how to download
your file. I tried both Firefox and Lynx.

[Richard Heathfield]

Re: problem with output of the program on different OS

Spiros Bousbouras said:

On 9 May, 07:20, pereges <Brol...@gmail. comwrote:

>On May 9, 10:52 am, Richard Heathfield <r...@see.sig.i nvalidwrote:
>>

Debuggers are over-rated by some people, and can be a huge time sink
if used flailingly.
Yes, I agree with you that the comment about design was misguided.
Module boundaries should be drawn to reflect differences in
functionality. The idea that you have some kind of Procrustean source
bed, such that any file longer than N lines must be split, is silly.
Is that zip file ready yet?

>>
>http://www.savefile.com/files/1547165

>
I've been to the page ; I don't see how to download
your file. I tried both Firefox and Lynx.

I struggled too, but managed it in the end. I copied it to my site, from
where you can easily get it:

http://www.cpax.org.uk/scratch/raytrace.zip

--
Richard Heathfield <http://www.cpax.org.uk >
Email: -http://www. +rjh@
Google users: <http://www.cpax.org.uk/prg/writings/googly.php>
"Usenet is a strange place" - dmr 29 July 1999