[Cocci] EXN question

[Cocci] EXN question

[Stan Sieler]

Hi,

I'm new to coccinelle.  I've just run spatch over about 300,000 lines of compiling C programs.
and was curious what the following meant:

   ...
   HANDLING: ./misc/pasnet.c
   EXN:Failure("lexing: empty token")
   ...

I did a binary search exercise :) ... and got the error down to one line:

   foo ('');

where foo was not declared (and had not been used earlier).

So, why was this code in there?  (I.e., how could it compile in C?)

Because it was within "#if 0 / #endif"!

It was Pascal code that was still to be translated to C.  
Thus, it was "commented out" (not actually a comment, of course, but similar effect).

We were quite surprised that spatch / coccinelle isn't ignoring stuff
(I won't say "code", because it's often non-code English text)
within "#if 0 / #endif" blocks, and feel this is a design flaw.

(BTW, I'm not referring to a macro that happens to evaluate to 0 ...
it's the five characters "#", "i", "f", " ", "0")

So far, I've only tested for the "!E & C" case, and it caught none (until I injected one as a test ... it properly caught that).

thanks,

Stan Sieler
sieler at allegro.com

[Cocci] EXN question

[Julia Lawall]

On Tue, 24 Feb 2015, Stan Sieler wrote:

> Hi,
> 
> I'm new to coccinelle.  I've just run spatch over about 300,000 lines of compiling C programs.
> and was curious what the following meant:
> 
>    ...
>    HANDLING: ./misc/pasnet.c
>    EXN:Failure("lexing: empty token")
>    ...
> 
> I did a binary search exercise :) ... and got the error down to one line:
> 
>    foo ('');
> 
> where foo was not declared (and had not been used earlier).
> 
> So, why was this code in there?  (I.e., how could it compile in C?)
> 
> Because it was within "#if 0 / #endif"!

Coccinelle is supposed to skip what is under if 0.  There has been a lot 
of changes to the management of ifdefs recently, and so this flag may have 
gotten inadvertently ignored.  I'll look into it.

julia

> It was Pascal code that was still to be translated to C.  
> Thus, it was "commented out" (not actually a comment, of course, but similar effect).
> 
> We were quite surprised that spatch / coccinelle isn't ignoring stuff
> (I won't say "code", because it's often non-code English text)
> within "#if 0 / #endif" blocks, and feel this is a design flaw.
> 
> (BTW, I'm not referring to a macro that happens to evaluate to 0 ...
> it's the five characters "#", "i", "f", " ", "0")
> 
> So far, I've only tested for the "!E & C" case, and it caught none (until I injected one as a test ... it properly caught that).
> 
> thanks,
> 
> Stan Sieler
> sieler at allegro.com
> 
> _______________________________________________
> Cocci mailing list
> Cocci at systeme.lip6.fr
> https://systeme.lip6.fr/mailman/listinfo/cocci
> 

[Cocci] Challenges around preprocessor statements?

[SF Markus Elfring]

> We were quite surprised that spatch / coccinelle isn't ignoring stuff
> (I won't say "code", because it's often non-code English text)
> within "#if 0 / #endif" blocks, and feel this is a design flaw.

The Coccinelle software works on a different abstraction level.

There is another feature request for text skipping in the waiting queue.
https://github.com/coccinelle/coccinelle/issues/20

Are there any more use cases to consider?
Would you eventually like to adjust source code between preprocessor
statements?

Regards,
Markus

[Cocci] EXN question

[Julia Lawall]

On Tue, 24 Feb 2015, Stan Sieler wrote:

> Hi,
>
> I'm new to coccinelle.  I've just run spatch over about 300,000 lines of compiling C programs.
> and was curious what the following meant:
>
>    ...
>    HANDLING: ./misc/pasnet.c
>    EXN:Failure("lexing: empty token")
>    ...
>
> I did a binary search exercise :) ... and got the error down to one line:
>
>    foo ('');

Hello,

If you still have it, could you send me a program that produces the
problem?  Because the C lexer explicitly does parse '' and I tried a
couple of examples and everything was fine.

julia

> where foo was not declared (and had not been used earlier).
>
> So, why was this code in there?  (I.e., how could it compile in C?)
>
> Because it was within "#if 0 / #endif"!
>
> It was Pascal code that was still to be translated to C.
> Thus, it was "commented out" (not actually a comment, of course, but similar effect).
>
> We were quite surprised that spatch / coccinelle isn't ignoring stuff
> (I won't say "code", because it's often non-code English text)
> within "#if 0 / #endif" blocks, and feel this is a design flaw.
>
> (BTW, I'm not referring to a macro that happens to evaluate to 0 ...
> it's the five characters "#", "i", "f", " ", "0")
>
> So far, I've only tested for the "!E & C" case, and it caught none (until I injected one as a test ... it properly caught that).
>
> thanks,
>
> Stan Sieler
> sieler at allegro.com
>
> _______________________________________________
> Cocci mailing list
> Cocci at systeme.lip6.fr
> https://systeme.lip6.fr/mailman/listinfo/cocci
>

[Cocci] Skipping of source code between preprocessor statements?

[SF Markus Elfring]

> Because the C lexer explicitly does parse ''

In which contexts does the syntax allow the use of single quotes
for the C programming language?


> and I tried a couple of examples and everything was fine.

How would you like to handle text within the construct "#if 0 / #endif"
by the analysis tool?

Regards,
Markus

[Cocci] Skipping of source code between preprocessor statements?

[Julia Lawall]

On Wed, 4 Mar 2015, SF Markus Elfring wrote:

> > Because the C lexer explicitly does parse ''
>
> In which contexts does the syntax allow the use of single quotes
> for the C programming language?

As far as I can tell, all.

>
>
> > and I tried a couple of examples and everything was fine.
>
> How would you like to handle text within the construct "#if 0 / #endif"
> by the analysis tool?

There is a flag for choosing whether to do this.

julia

[Cocci] Skipping of source code between preprocessor statements?

[SF Markus Elfring]

>> In which contexts does the syntax allow the use of single quotes
>> for the C programming language?
> 
> As far as I can tell, all.

Are they only valid within comments and string literals?


>> How would you like to handle text within the construct "#if 0 / #endif"
>> by the analysis tool?
> 
> There is a flag for choosing whether to do this.

Do you refer to the undocumented command line parameter "noif0-passing"?

Regards,
Markus

[Cocci] Skipping of source code between preprocessor statements?

[Julia Lawall]

On Wed, 4 Mar 2015, SF Markus Elfring wrote:

> >> In which contexts does the syntax allow the use of single quotes
> >> for the C programming language?
> >
> > As far as I can tell, all.
>
> Are they only valid within comments and string literals?

Coccinelle doesn't care if they are valid or not.  Once the lexer accepts
'' as a character, no subsequent part of coccinelle should noitce.

> >> How would you like to handle text within the construct "#if 0 / #endif"
> >> by the analysis tool?
> >
> > There is a flag for choosing whether to do this.
>
> Do you refer to the undocumented command line parameter "noif0-passing"?

Undoubtedly.

julia