From: "H.J. Lu" <hjl.tools@gmail.com>
To: Fangrui Song <i@maskray.me>
Cc: Binutils <binutils@sourceware.org>,
GNU gABI gnu-gabi <gnu-gabi@sourceware.org>
Subject: Re: [PATCH v2] Support for SHF_GNU_RETAIN ELF Section Flag
Date: Tue, 29 Sep 2020 12:54:52 -0700 [thread overview]
Message-ID: <CAMe9rOrkFHHjX5mZ6Jn=h4Rd3_BpQxZBozi--S5NKd60ftp70w@mail.gmail.com> (raw)
In-Reply-To: <20200929193806.m6u6ra6oijqkstfo@gmail.com>
On Tue, Sep 29, 2020 at 12:38 PM Fangrui Song <i@maskray.me> wrote:
>
> >>
> >> // 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)
> >>
> >
> >There is no error in this case.
> >The original patch handled it, and it has been further improved in v2.
> >There's even a testcase testing exactly the functionality you say is
> >broken.
> >
> > gas/testsuite/gas/elf/section22.s:
> > .section .bss,"aw"
> > ...
> > .section .bss,"awR",%nobits
> >
> >I already gave a detailed response to your reloc proposal:
> >https://sourceware.org/pipermail/binutils/2020-September/113450.html
>
> Letting the following assembly creates two .bss sections adds an exception to
> "gas: error for section type, attr, or entsize change"
> (https://sourceware.org/pipermail/binutils/2020-February/109945.html)
> for which I have achieved consensus with Alan Modra and some LLVM
> toolchain folks. That is why I hope we could re-consider this design
> choice.
>
> .section .bss,"aw"
> .section .bss,"awR",%nobits
>
FWIW, GNU assembler has been able to create multiple sections with
the same section name for a while. For SHF_GNU_RETAIN, we added
+/* Create unique input sections for sections with the same name, but different
+ values for the flags in this mask. */
+#define SEC_ASSEMBLER_SHF_MASK SHF_GNU_RETAIN
to control when to create a new section with the same section name.
For other cases, no new section is created.
--
H.J.
next prev parent reply other threads:[~2020-09-29 19:55 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20200928132613.btkqaoomv4fdnupn@jozef-acer-manjaro>
[not found] ` <20200929044353.vx26ypc2oioqbmfb@gmail.com>
[not found] ` <20200929100442.o3e66jbmqpv5cajh@jozef-acer-manjaro>
2020-09-29 19:38 ` Fangrui Song
2020-09-29 19:54 ` H.J. Lu [this message]
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
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