From: Fangrui Song <i@maskray.me>
To: binutils@sourceware.org
Subject: Re: [PATCH v2] Support for SHF_GNU_RETAIN ELF Section Flag
Date: Mon, 28 Sep 2020 21:43:53 -0700 [thread overview]
Message-ID: <20200929044353.vx26ypc2oioqbmfb@gmail.com> (raw)
In-Reply-To: <20200928132613.btkqaoomv4fdnupn@jozef-acer-manjaro>
On 2020-09-28, Jozef Lawrynowicz wrote:
>The attached patch is version 2 of the SHF_GNU_RETAIN patch that was
>previously discussed here:
>https://sourceware.org/pipermail/binutils/2020-September/113406.html
>
>The following changes have been made:
>- Removed the .retain directive
>- The assembler will create different input sections for sections with
> the same name but SHF_GNU_RETAIN set/unset (thanks to H.J. for that).
> This means the linker will be able to do a better job garbage
> collecting input sections, as the "retain" attribute applied to a
> symbol declaration in the source code will not cause other parts of
> the program that are not required, but are in the same section, to be
> unnecessarily retained.
>- Added GNU OSABI handling (also thanks to H.J.).
My point from https://sourceware.org/pipermail/binutils/2020-September/113466.html stands.
Section flags are a bit cumbersome. If the following
// a.h
__attribute__((section("sec")))
inline void bar() { ... }
// a.c
#include "a.h"
__attribute__((section("sec"), retain))
void foo() {
}
compiles to
.section sec,"a",@progbits
...
.section sec,"aR",@progbits
...
You will get a gas error for changing section flags
(https://sourceware.org/pipermail/binutils/2020-February/109945.html)
.reloc is really convenience in this case. You can add as many .reloc
directives as you like, each contributing one R_*_NONE to the object
file but zero cost to the linked image.
next prev parent reply other threads:[~2020-09-29 4:43 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-28 13:26 Jozef Lawrynowicz
2020-09-29 4:43 ` Fangrui Song [this message]
2020-09-29 10:04 ` Jozef Lawrynowicz
2020-09-29 19:38 ` Fangrui Song
2020-09-29 19:54 ` H.J. Lu
2020-09-29 21:37 ` Jozef Lawrynowicz
2020-09-30 0:10 ` Roland McGrath
2020-09-30 10:18 ` Jozef Lawrynowicz
2020-09-30 14:01 ` H.J. Lu
2020-10-01 19:22 ` Fangrui Song
2020-10-01 19:53 ` H.J. Lu
2020-10-02 12:44 ` Jozef Lawrynowicz
2020-09-30 14:13 ` Michael Matz
2020-09-30 22:13 ` H.J. Lu
2020-10-01 10:50 ` Jozef Lawrynowicz
2020-10-01 11:39 ` Alan Modra
2020-10-02 12:30 ` Jozef Lawrynowicz
2020-10-02 12:33 ` H.J. Lu
2020-10-02 12:41 ` H.J. Lu
2020-10-02 12:53 ` Jozef Lawrynowicz
2020-10-02 14:11 ` Alan Modra
2020-10-02 15:45 ` Jozef Lawrynowicz
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