Bug in _VFPRINTF_R

[Samuel Vinson]

Yes you are right, I forgot to mention len = 0.
I'm sorry.

Samuel

Matt Gessner a écrit :
> First, apologies because the first email I posted in response was sent before I finished editing it.
>
>   
>> I'm sorry Eric, but I gave you a specific example :
>>     printf("%.*s\n",len,(char *)NULL) /* len = 0 */
>>
>> and not printf("%s", (char *)NULL)
>>
>>     
>
> Actually, you did NOT use that as your example.
>
> You posted:
>
> *******************************************************************
> Hi,
>
> In newlib printf, snprintf (perhaps others string functions) use 
> _VFPRINTF_R.
> So if you call :   
>     printf("%.*s\n",len,(char *)NULL)   
>     snprintf(ptr, 40, "%.*s", len, (char *)NULL)
> You obtain :
>     (null)
>     ptr = "(null)"
>
> *******************************************************************
>
> Never did you mention anywhere that len == 0.
>
> That drastically changes the meaning of the code you originally posted, and while I don't have the code in front of me, the len == 0 case is not going to be processed in the precise section where you originally posted your change.
>
> FWIW, I think your suggested behaviour makes sense, for snprintf, but not for printf.
>
>   
>> In my example, I think the result should be empty an not (null)
>>
>> Samuel
>>
>> Eric Blake a écrit :
>>     
>>> -----BEGIN PGP SIGNED MESSAGE-----
>>> Hash: SHA1
>>>
>>> According to Samuel Vinson on 9/15/2007 1:35 AM:
>>>
>>>       
>>>> I never see that with different libc implementation, I used
>>>> (linux/gcc/libc/glibc, windows/msvcrt, solaris/libc...)
>>>>
>>>>         
>>> It may not match msvcrt or solaris libc, but it does match glibc - I'm
>>>       
>> not
>>     
>>> sure how you tested it.
>>>
>>>
>>>       
>>>> Perhaps POSIX and C99 allow your choice, but this is not portable in
>>>> different platforms.
>>>>
>>>>         
>>> This is not portable, period.  Calling printf("%s", (char*)NULL) invokes
>>> undefined behavior, and is a bug in your program, not in newlib.
>>>
>>> - --
>>> Don't work too hard, make some time for fun as well!
>>>
>>> Eric Blake             ebb9@byu.net
>>> -----BEGIN PGP SIGNATURE-----
>>> Version: GnuPG v1.4.5 (Cygwin)
>>> Comment: Public key at home.comcast.net/~ericblake/eblake.gpg
>>> Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org
>>>
>>> iD8DBQFG68gr84KuGfSFAYARAr2PAKCR56DlvOvhKZXMeDn+ecmYO7fXEQCeMEUV
>>> kGk4bBxoFTk2hpRD3TiakLM=
>>> =LIb4
>>> -----END PGP SIGNATURE-----
>>>
>>>
>>>
>>>       
>
>
>
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