Re: question about prctl return value type

[Yang Xu <xuyang2018.jy@cn.fujitsu.com>]

on 2019/07/24 18:48, Florian Weimer wrote:

> * Yang Xu:
>
>> Since kernel syscall use long value for return, why we set int in
>> sys/prctl.h(glibc). as below:
>>
>> /include/sys/prctl.h
>>
>>    1 #ifndef _SYS_PRCTL_H
>>    2 #include_next <sys/prctl.h>
>>    3 
>>    4 # ifndef _ISOMAC
>>    5 
>>    6 extern int __prctl (int __option, ...);
>>    7 
>>    8 # endif /* !_ISOMAC */
>>    9 #endif
> Note that the actual user-visible header is
> sysdeps/unix/sysv/linux/sys/prctl.h, but it has the same issue.
>
>> If we calling prctl(PR_SET_TIMERSLACK, ULONG_MAX) and then calling prctl(PR_GET_TIMERSLACK), the value
>> will be truncated into INT_MAX(or convered into unsinged,it is UINT_MAX) on 64bit machine. Or, this is a 
>> glibc limitation for prctl interfaces?
> I think this is a glibc limitation/bug.  The return type should probably
> be __register_t (a type that is currently woefully underused).  We
> cannot simply change the return time because once applications are built
> against the new prototype, we need to ensure that they also use the new
> glibc.
>
> Would you please file a bug for this?
> <https://sourceware.org/bugzilla/> is our bug tracker.

Hi Florian

I create a bug and cc you, url as below:
https://sourceware.org/bugzilla/show_bug.cgi?id=24850


Thanks 
Yang Xu

> Thanks,
> Florian
>
>
>