From: ludo@gnu.org (Ludovic Courtès)
To: Chaos Eternal <chaoseternal@shlug.org>
Cc: 18592@debbugs.gnu.org
Subject: bug#18592: FFI should have portable access to ‘errno’
Date: Mon, 19 Jan 2015 21:22:11 +0100 [thread overview]
Message-ID: <87h9vmy0zw.fsf@gnu.org> (raw)
In-Reply-To: <CAGyY8NtoipsEyhp6iMTWMXJ1aV2RHtq8tehSbSLqwoV+J_yJ6w@mail.gmail.com> (Chaos Eternal's message of "Sun, 23 Nov 2014 01:53:35 +0800")
Hi,
Sorry for the long delay.
Chaos Eternal <chaoseternal@shlug.org> skribis:
> Proposals to solve this bug:
>
> Proposal 1.
>
> Adding a keyword argument to pointer->procedure, if set to true, the
> generated wrapper will check 'errno' immediately after ffi_call and
> return the errno as second value.
>
> the proposed pointer->procedure maybe like this:
> pointer->procedure return_type func_ptr arg_types #:return-errno
>
> Proposal 2.
>
> let pointer->procedure check return_type, if it is a list:
> (func_return_type, 'errno)
> then return multiple values, as errno be second value.
That’s my favorite because it’s both pragmatic and extensible (we can
also add support for h_errno, etc.)
> Proposal 3.
>
> introduce another procedure "pointers->procedure", which will pack
> multiple function pointer into one procedure, in this procedure, the
> packed functions will be called in sequence, and their return value
> will be returned as multiple values.
>
> the interface would be like this:
> pointers->procedure (list-of-return-type) (list-of-pointers) (list-of arg-defs)
>
> also, we need a simple c-function deref-pointer-to-int, which will
> de-reference a pointer and return it's int value.
>
> using above tools, a proper system call with errno be returned could
> be like this:
>
> ((pointers->procedure
> (list int int)
> (list pointer-of-inotify-add-watch pointer-of-deref-pointer-to-int)
> (list (list int '* int) (list '*)))
> (list inotify-fd "path-to-watch" watch-flag) (list pointer-of-errno))
The problem is that POINTER-OF-ERRNO does not necessarily exist and
cannot be obtained portably.
Also, I find the interface a bit clumsy.
So my support goes to #2. Would you like to give it a try?
Thanks for your input!
Ludo’.
next prev parent reply other threads:[~2015-01-19 20:22 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-09-30 20:17 bug#18592: FFI should have portable access to ‘errno’ Frank Terbeck
2014-11-11 15:03 ` Mark H Weaver
2014-11-11 20:02 ` Frank Terbeck
2014-11-13 17:12 ` Mark H Weaver
2014-11-22 17:53 ` Chaos Eternal
2015-01-19 20:22 ` Ludovic Courtès [this message]
2015-01-24 8:08 ` Mark H Weaver
2015-01-24 8:22 ` Mark H Weaver
2015-01-24 10:33 ` Ludovic Courtès
2015-12-31 12:33 ` Nala Ginrut
2016-01-04 12:04 ` Nala Ginrut
2016-01-04 16:12 ` Mark H Weaver
2016-01-04 19:14 ` Nala Ginrut
2016-01-05 2:24 ` Chaos Eternal
2016-01-05 7:49 ` tomas
2016-01-05 8:38 ` Nala Ginrut
2016-01-05 15:08 ` Mark H Weaver
2016-01-05 19:21 ` Nala Ginrut
2016-02-18 8:25 ` Nala Ginrut
2016-02-18 13:30 ` Mark H Weaver
2016-02-19 5:02 ` Nala Ginrut
2016-02-26 11:18 ` Nala Ginrut
2016-03-03 17:36 ` Mark H Weaver
2016-03-03 20:32 ` tomas
2016-03-13 17:06 ` Nala Ginrut
2016-06-20 19:55 ` Mark H Weaver
2016-01-05 15:40 ` Mark H Weaver
2016-01-04 16:21 ` Mark H Weaver
2015-01-25 20:59 ` guile
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