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From: Christian Lindig <christian.lindig@citrix.com>
To: Ian Jackson <Ian.Jackson@citrix.com>
Cc: Xen-devel <xen-devel@lists.xenproject.org>,
	Jonathan Ludlam <Jonathan.Ludlam@citrix.com>,
	Roger Pau Monne <roger.pau@citrix.com>,
	Wei Liu <wei.liu2@citrix.com>,
	"dave@recoil.org" <dave@recoil.org>
Subject: Re: [PATCH for-4.9 2/2] oxenstored: make it work on FreeBSD
Date: Tue, 18 Apr 2017 10:22:45 +0000	[thread overview]
Message-ID: <CFB8AD83-E9AB-441B-8E7F-A73B3F13BE5B@citrix.com> (raw)
In-Reply-To: <22773.59283.370168.112825@mariner.uk.xensource.com>


> On 18. Apr 2017, at 11:16, Ian Jackson <ian.jackson@eu.citrix.com> wrote:
> 
> Wei Liu writes ("[PATCH for-4.9 2/2] oxenstored: make it work on FreeBSD"):
>> Call the uname syscall to determine sysname and return device names
>> accordingly.
> ...
>> -let xenstored_proc_kva = "/proc/xen/xsd_kva"
>> -let xenstored_proc_port = "/proc/xen/xsd_port"
>> +let xenstored_proc_kva =
>> +  let info = Unix_syscalls.uname () in
>> +  match info.sysname with
>> +  | "Linux" -> "/proc/xen/xsd_kva"
>> +  | "FreeBSD" -> "/dev/xen/xenstored"
>> +  | _ -> "nonexistent"
> 
> This isn't very good.  If this code wants to fail, it returns a string
> "nonexistent" which would then be used to construct pathnames, and
> actually accessed.
> 
> In Haskell one could simply leave the default case off, which would
> generate a runtime failure.  Is that possible in ocaml ?

In Ocaml you would either use “assert false” or raise a dedicated exception for the catch-all case. You would get a run-time Match_failure exception without but this is nasty. The current solution has the problem you describe.

— C 

 
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  reply	other threads:[~2017-04-18 10:22 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-04-14 10:20 [PATCH for-4.9 0/2] oxenstored: make it work on FreeBSD Wei Liu
2017-04-14 10:20 ` [PATCH for-4.9 1/2] oxenstored: add an Unix syscall C extension Wei Liu
2017-04-18 10:14   ` Ian Jackson
2017-04-14 10:20 ` [PATCH for-4.9 2/2] oxenstored: make it work on FreeBSD Wei Liu
2017-04-14 10:32   ` [PATCH for-4.9] oxenstored: remove "_proc" in names Wei Liu
2017-04-18 10:15     ` Ian Jackson
2017-04-18 10:16   ` [PATCH for-4.9 2/2] oxenstored: make it work on FreeBSD Ian Jackson
2017-04-18 10:22     ` Christian Lindig [this message]
2017-04-18  9:46 ` [PATCH for-4.9 0/2] " Christian Lindig
2017-04-18  9:59   ` Wei Liu
2017-04-18 10:11     ` Christian Lindig
2017-04-18 10:11     ` Christian Lindig
2017-04-18 13:07       ` Wei Liu

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