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From: Yang Xu <xuyang2018.jy@cn.fujitsu.com>
To: <libc-help@sourceware.org>
Subject: question about prctl return value type
Date: Wed, 24 Jul 2019 10:01:00 -0000	[thread overview]
Message-ID: <5D382C5F.6020806@cn.fujitsu.com> (raw)

Hi All

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

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?

ps:After kernel commit da8b44d5a9f ("timer: convert timer_slack_ns from unsigned long to u64"),
we limit under ULONG_MAX when calling PR_GET_TIMERSLACK. I think we can use long instead of int in sys/prctl.h.

Thanks
Yang Xu 



             reply	other threads:[~2019-07-24 10:01 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-07-24 10:01 Yang Xu [this message]
2019-07-24 10:48 ` Florian Weimer
2019-07-25  7:53   ` Yang Xu

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