[Bug target/59842] New: `__x86.get_pc_thunk.bx' referenced in section `.text': defined in discarded section…

[Bug target/59842] New: `__x86.get_pc_thunk.bx' referenced in section `.text': defined in discarded section…

[tg at mirbsd dot org]

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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59842

            Bug ID: 59842
           Summary: `__x86.get_pc_thunk.bx' referenced in section `.text':
                    defined in discarded section…
           Product: gcc
           Version: 4.8.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: tg at mirbsd dot org

Created attachment 31855
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=31855&action=edit
test runner

Hi *,

I originally filed this as Debian #735564 but a user informed me they are also
seeing this on other GNU/Linux distributions, and with GCC 4.7.1 on Slackware.

Since a while, I’m getting errors like these:

`__x86.get_pc_thunk.bx' referenced in section `.text' of x3.o: defined in
discarded section `.text.__x86.get_pc_thunk.bx[__x86.get_pc_thunk.bx]' of x3.o

I used to be able to avoid them (although, back then, the symbol
was named “__i686.get_pc_thunk.bx”) by adding -march=i486, but
this no longer helps.

Screen log (the files x.sh, x.i and x.sym are attached):

tglase@tglase:~ $ mksh x.sh
`__x86.get_pc_thunk.bx' referenced in section `.text' of x3.o: defined in
discarded section `.text.__x86.get_pc_thunk.bx[__x86.get_pc_thunk.bx]' of x3.o
`__x86.get_pc_thunk.bx' referenced in section `.text' of x3.o: defined in
discarded section `.text.__x86.get_pc_thunk.bx[__x86.get_pc_thunk.bx]' of x3.o
`__x86.get_pc_thunk.bx' referenced in section `.text' of x3.o: defined in
discarded section `.text.__x86.get_pc_thunk.bx[__x86.get_pc_thunk.bx]' of x3.o
`__x86.get_pc_thunk.bx' referenced in section `.text' of x3.o: defined in
discarded section `.text.__x86.get_pc_thunk.bx[__x86.get_pc_thunk.bx]' of x3.o
`__x86.get_pc_thunk.bx' referenced in section `.text' of x3.o: defined in
discarded section `.text.__x86.get_pc_thunk.bx[__x86.get_pc_thunk.bx]' of x3.o
`__x86.get_pc_thunk.bx' referenced in section `.text' of x3.o: defined in
discarded section `.text.__x86.get_pc_thunk.bx[__x86.get_pc_thunk.bx]' of x3.o
`__x86.get_pc_thunk.bx' referenced in section `.text' of x3.o: defined in
discarded section `.text.__x86.get_pc_thunk.bx[__x86.get_pc_thunk.bx]' of x3.o
`__x86.get_pc_thunk.bx' referenced in section `.text' of x3.o: defined in
discarded section `.text.__x86.get_pc_thunk.bx[__x86.get_pc_thunk.bx]' of x3.o
`__x86.get_pc_thunk.bx' referenced in section `.text' of x3.o: defined in
discarded section `.text.__x86.get_pc_thunk.bx[__x86.get_pc_thunk.bx]' of x3.o
`__x86.get_pc_thunk.bx' referenced in section `.text' of x3.o: defined in
discarded section `.text.__x86.get_pc_thunk.bx[__x86.get_pc_thunk.bx]' of x3.o
`__x86.get_pc_thunk.bx' referenced in section `.text' of x3.o: defined in
discarded section `.text.__x86.get_pc_thunk.bx[__x86.get_pc_thunk.bx]' of x3.o
collect2: error: ld returned 1 exit status

IMHO, GCC may not mark symbols as discardable that it uses by itself. Adding
this to the symbol file is no solution either, as this becomes highly platform-
and compiler-dependent.
>From gcc-bugs-return-440558-listarch-gcc-bugs=gcc.gnu.org@gcc.gnu.org Thu Jan 16 14:48:07 2014
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From: "tg at mirbsd dot org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug target/59842] `__x86.get_pc_thunk.bx' referenced in section `.text':=?UTF-8?Q? defined in discarded section…?Date: Thu, 16 Jan 2014 14:48:00 -0000
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http://gcc.gnu.org/bugzilla/show_bug.cgi?idY842

--- Comment #1 from Thorsten Glaser <tg at mirbsd dot org> ---
Created attachment 31856
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id1856&actioníit
preprocessed source code

[Bug target/59842] `__x86.get_pc_thunk.bx' referenced in section `.text': defined in discarded section…

[tg at mirbsd dot org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59842

--- Comment #2 from Thorsten Glaser <tg at mirbsd dot org> ---
Created attachment 31857
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=31857&action=edit
symbols file

[Bug target/59842] `__x86.get_pc_thunk.bx' referenced in section `.text': defined in discarded section…

[tg at mirbsd dot org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59842

Thorsten Glaser <tg at mirbsd dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Target|                            |i486-linux-gnu
                URL|                            |http://bugs.debian.org/cgi-
                   |                            |bin/bugreport.cgi?bug=73556
                   |                            |4
      Known to work|                            |4.6.4
               Host|                            |i486-linux-gnu
      Known to fail|                            |4.7.1, 4.8.2
              Build|                            |i486-linux-gnu

--- Comment #3 from Thorsten Glaser <tg at mirbsd dot org> ---
Adding extra info. GCC 4.6 (Debian sid) works iff you add -march=i486 but
exhibits the same problem (with different symbol) otherwise. GCC 3.4.6 (MirBSD)
works.

[Bug target/59842] `__x86.get_pc_thunk.bx' referenced in section `.text': defined in discarded section…

[pinskia at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59842

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                URL|http://bugs.debian.org/cgi- |
                   |bin/bugreport.cgi?bug=73556 |
                   |4                           |
           See Also|                            |http://bugs.debian.org/7355
                   |                            |64

--- Comment #4 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
I don't think this is a GCC bug but rather a bug using objcopy and thinking
that will not get rid of hidden global symbols.

The .text.__x86.get_pc_thunk.[bc]x symbols are defined as:
        .section       
.text.__x86.get_pc_thunk.cx,"axG",@progbits,__x86.get_pc_thunk.cx,comdat
        .globl  __x86.get_pc_thunk.cx
        .hidden __x86.get_pc_thunk.cx
        .type   __x86.get_pc_thunk.cx, @function
__x86.get_pc_thunk.cx:
.LFB15:
        .cfi_startproc
        movl    (%esp), %ecx
        ret
        .cfi_endproc
.LFE15:
        .section       
.text.__x86.get_pc_thunk.bx,"axG",@progbits,__x86.get_pc_thunk.bx,comdat
        .globl  __x86.get_pc_thunk.bx
        .hidden __x86.get_pc_thunk.bx
        .type   __x86.get_pc_thunk.bx, @function
__x86.get_pc_thunk.bx:
.LFB16:
        .cfi_startproc
        movl    (%esp), %ebx
        ret

So they are already hidden so when doing the final link they will not show up
in the shared library.  The objcopy is removing the symbol names for these
section which is invalid as they are comdat and cannot be removed.


Really the code should move over to a versioning script instead of using
objcopy and that would work much better and be slightly more portable.

[Bug target/59842] `__x86.get_pc_thunk.bx' referenced in section `.text': defined in discarded section…

[tg at mirbsd dot org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59842

--- Comment #5 from Thorsten Glaser <tg at mirbsd dot org> ---
Hm, unsure. These versioning scripts are pretty much recent GNU stuff. But if
you have input…

cvs -d _anoncvs@anoncvs.mirbsd.org:/cvs co -PA -d xchat-randex
contrib/hosted/tg/code/xchat-randex
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Subject: [Bug target/59842] `__x86.get_pc_thunk.bx' referenced in section `.text':=?UTF-8?Q? defined in discarded section…?Date: Thu, 16 Jan 2014 17:58:00 -0000
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http://gcc.gnu.org/bugzilla/show_bug.cgi?idY842

--- Comment #6 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Thorsten Glaser from comment #5)
> Hm, unsure. These versioning scripts are pretty much recent GNU stuff.

Recent as in the last 10 years maybe.  But not in the last 5 years.  Also they
are supported in Solaris and even Darwin too.

[Bug target/59842] `__x86.get_pc_thunk.bx' referenced in section `.text': defined in discarded section…

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=59842

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|---                         |MOVED
           See Also|                            |https://sourceware.org/bugz
                   |                            |illa/show_bug.cgi?id=27931

--- Comment #7 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
objcopy bug filed just recently:
https://sourceware.org/bugzilla/show_bug.cgi?id=27931

So closing as moved.

[Bug target/59842] `__x86.get_pc_thunk.bx' referenced in section `.text': defined in discarded section…

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=59842

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           See Also|                            |https://sourceware.org/bugz
                   |                            |illa/show_bug.cgi?id=3182

--- Comment #8 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Or it is fixed by https://sourceware.org/bugzilla/show_bug.cgi?id=3182 .

Either way it is a binutils objcopy issue and not a GCC one really.