From: Alan Modra <amodra@gmail.com>
To: Ian Taylor <iant@golang.org>
Cc: Richard Henderson <rth@redhat.com>,
"Lynn A. Boger" <laboger@linux.vnet.ibm.com>,
gcc-patches <gcc-patches@gcc.gnu.org>,
libffi-discuss@sourceware.org,
"gofrontend-dev@googlegroups.com"
<gofrontend-dev@googlegroups.com>,
Ian Lance Taylor <ian@airs.com>
Subject: Re: [gofrontend-dev] Re: [PATCH 00/13] Go closures, libffi, and the static chain
Date: Fri, 07 Nov 2014 23:55:00 -0000 [thread overview]
Message-ID: <20141107235446.GE3990@bubble.grove.modra.org> (raw)
In-Reply-To: <CAOyqgcXEqWGRhm50te3mvsh=owSrUAmtrg4EKJ70f_BDBaqtOQ@mail.gmail.com>
On Fri, Nov 07, 2014 at 08:06:52AM -0800, Ian Taylor wrote:
> Closures exist only for nested functions and for functions created by
> reflect.MakeFunc and friends.
>
> Storing a top-level function into a variable will give you something
> that looks like it has a closure, but the closure will always be empty
> and it will never be used. The indirect call will set the closure
> value in the static chain register, but the register will not be used
> by the function being called.
Good, this was something I was still worried about, because the mere
fact that a call is indirect doesn't guarantee it won't hit a plt
stub. Many ABIs define the address of a non-local function in an
executable to be the address of the plt stub code for that function.
So it is quite possible for an indirect call to bounce through a plt
stub. Various linker optimisations make this fairly uncommon, for
instance the GNU powerpc linkers won't do this unless the function
address is taken in the executable by non-PIC (see
pointer_equality_needed in BFD code).
--
Alan Modra
Australia Development Lab, IBM
next prev parent reply other threads:[~2014-11-07 23:55 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-10-10 20:43 Richard Henderson
2014-10-10 20:43 ` [PATCH 04/13] Use the static chain as the closure parameter from Go Richard Henderson
2014-10-10 20:43 ` [PATCH 11/13] libffi: Support go closures on aarch64 Richard Henderson
2014-10-10 20:43 ` [PATCH 10/13] libffi: Rewrite aarch64 Richard Henderson
2014-10-10 20:43 ` [PATCH 12/13] libffi: Rewrite i386 sysv Richard Henderson
2014-10-10 20:43 ` [PATCH 05/13] libgo: Use the static chain for the closure Richard Henderson
2014-10-10 20:43 ` [PATCH 03/13] HACK! Allow the static chain to be set from C Richard Henderson
2014-10-11 0:33 ` Ian Lance Taylor
[not found] ` <CAMn1gO7vJOcNi218p9m32de_rrnKBrUcGF-EKP3dJwaL+8BtUw@mail.gmail.com>
2014-10-11 1:42 ` [gofrontend-dev] " Peter Collingbourne
2014-10-11 4:24 ` Richard Henderson
2014-10-13 8:10 ` Richard Biener
2014-10-13 18:46 ` Peter Collingbourne
2014-10-14 18:44 ` [PATCH v2 03/13] " Richard Henderson
2014-10-10 20:43 ` [PATCH 13/13] libffi: Support go closures on i386 Richard Henderson
2014-10-10 20:43 ` [PATCH 06/13] libffi: Add entry points for interacting with Go Richard Henderson
2014-10-10 20:43 ` [PATCH 01/13] Make TARGET_STATIC_CHAIN allow a function type Richard Henderson
2014-10-10 20:43 ` [PATCH 09/13] libgo: Remove __go_get/set_closure Richard Henderson
2014-10-10 20:43 ` [PATCH 02/13] Allow the front-end to create calls with a static chain Richard Henderson
2014-10-10 20:43 ` [PATCH 08/13] libgo: Use the new libffi interfaces for Go Richard Henderson
2014-10-10 20:43 ` [PATCH 07/13] libffi: Support go closures on x86_64 Richard Henderson
2014-10-11 0:23 ` [PATCH 00/13] Go closures, libffi, and the static chain Ian Lance Taylor
2014-11-05 21:34 ` Lynn A. Boger
2014-11-06 6:59 ` Richard Henderson
2014-11-06 12:48 ` Alan Modra
2014-11-06 13:04 ` Richard Henderson
2014-11-06 17:45 ` [gofrontend-dev] " Ian Taylor
2014-11-07 7:39 ` Richard Henderson
2014-11-07 8:50 ` Jay
2014-11-07 16:06 ` Ian Taylor
2014-11-07 23:55 ` Alan Modra [this message]
2014-11-06 13:10 ` Lynn A. Boger
2014-11-06 13:17 ` Richard Henderson
2014-12-11 9:06 ` Dominik Vogt
2014-12-11 9:21 ` Alan Modra
2014-12-11 10:31 ` [gofrontend-dev] " Dominik Vogt
2014-12-11 12:25 ` Dominik Vogt
2014-12-11 19:56 ` Richard Henderson
2014-12-12 12:06 ` Dominik Vogt
2014-12-12 18:14 ` Richard Henderson
2014-12-15 9:42 ` Dominik Vogt
2014-12-15 20:11 ` Richard Henderson
2014-12-12 13:57 ` Dominik Vogt
2014-12-11 19:38 ` Richard Henderson
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