Re: [csmith-dev] --max-pointer-depth not honored?

[Xuejun Yang <xuyang@microsoft.com>]

Unfortunately no. It seems we are upholding the rule only when generating l-values.  Probably need to do the same thing while creating other expressions.

-Xuejun

-----Original Message-----
From: csmith-dev-bounces@flux.utah.edu [mailto:csmith-dev-bounces@flux.utah.edu] On Behalf Of John Regehr
Sent: Tuesday, October 20, 2015 1:36 PM
To: csmith-dev@flux.utah.edu
Subject: Re: [csmith-dev] --max-pointer-depth not honored?

Is there a workaround Xuejun?

John



On 10/20/15 10:33 PM, Xuejun Yang wrote:
> It’s obviously a bug in Csmith. Your understanding is correct.
> "--max-pointer-depth"should be the one to limit indirection level for 
> pointer deference and other usages.
>
> *From:*csmith-dev-bounces@flux.utah.edu
> [mailto:csmith-dev-bounces@flux.utah.edu] *On Behalf Of *Tahina 
> Ramananandro
> *Sent:* Tuesday, October 20, 2015 12:59 PM
> *To:* csmith-dev@flux.utah.edu
> *Subject:* [csmith-dev] --max-pointer-depth not honored?
>
> Dear Csmith developers,
>
> I have been testing Csmith 2.2.0 (Git version dcef523), and I am 
> trying to understand the meaning of the --max-pointer-depth option.
>
> If I understood well, Csmith with --max-pointer-depth N should produce 
> a program with pointer-dereferencing expressions of length at most N+1 
> (i.e. without pointer dereferences of the form *..*x with N+2 stars or
> more.)
>
> However, with --max-pointer-depth 0, I still managed to produce the 
> attached C program with a depth-2 pointer dereference  (and similarly, 
> with --max-pointer-depth 1 and a depth-3 pointer dereference, although 
> in the latter case, it is hard to generate such programs if shorter 
> than
> 400 lines).
>
> Moreover, massive tests show that, with --no-checksum --no-argc
>   --no-arrays --no-bitfields --no-structs --no-unions 
> --max-pointer-depth 1, more than 70% of all programs generated by 
> Csmith (regardless of their sizes) reach pointer dereference level 3 
> or more (sometimes up to 8).
>
> So, is my understanding correct?
>
> - If so, is there a bug in Csmith that makes --max-pointer-depth not 
> properly honored?
>
> - Otherwise, what should be the exact meaning of this option, and 
> which use cases were intended? How could I control the maximum pointer 
> dereference level in Csmith-generated programs?
>
> And then, a final question too: even though it might be possible to 
> limit the level of pointer dereference expressions, is there a way to 
> limit the depth of pointer types?
>
> Thank you in advance for your help.
>
> Best regards,
>
> --
>
> Tahina Oliver Ramananandro, Ph. D.
>
> Senior Engineer, Advanced Compilers and Formal Verification
>
> Reservoir Labs, Inc.
>
> 632 Broadway, Suite 803
>
> New York, NY 10012
>
> USA
>
> Phone: +1 (212) 780-0527 ext. 157
>
> E-mail: ramananandro@reservoir.com 
> <mailto:ramananandro@reservoir.com>,
> tahina@ramananandro.org <mailto:tahina@ramananandro.org>
>
> Web: 
> https://na01.safelinks.protection.outlook.com/?url=http%3a%2f%2ftahina
> .ramananandro.org&data=01%7c01%7cxuyang%40microsoft.com%7cf298a48b066f
> 448203ca08d2d98ec56a%7c72f988bf86f141af91ab2d7cd011db47%7c1&sdata=%2bM
> iowWq9A1%2f77L%2fDaLlHf41LQNFhXOABTp0pREmBWlc%3d
> <https://na01.safelinks.protection.outlook.com/?url=http%3a%2f%2ftahin
> a.ramananandro.org&data=01%7c01%7cxuyang%40microsoft.com%7c6ee7ac19d63
> 0425d5e3308d2d9896cc5%7c72f988bf86f141af91ab2d7cd011db47%7c1&sdata=Opb
> %2f%2bvTUJpjUQyQDT%2fAaWjf1j9W1u%2bYjFWW%2fw%2bI422k%3d>
>
> Notes:
>
> [#] Here I consider that --max-pointer-depth 0 does not prevent Csmith 
> from producing pointers at large, by contrast to --no-pointers
>