[Bug c++/64697] New: C++11 thread_local: relocation truncated to fit: R_X86_64_PC32 against undefined symbol `TLS init function for N::ptd'

[Bug c++/64697] New: C++11 thread_local: relocation truncated to fit: R_X86_64_PC32 against undefined symbol `TLS init function for N::ptd'

[vhaisman at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64697

            Bug ID: 64697
           Summary: C++11 thread_local: relocation truncated to fit:
                    R_X86_64_PC32 against undefined symbol `TLS init
                    function for N::ptd'
           Product: gcc
           Version: 4.9.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: vhaisman at gmail dot com

I have hit an issue with thread-local storage variables on
Cygwin/AMD64, I do not see it with Cygwin/i686.

I am having linking issues when using `thread_local` keyword in Cygwin
with its GCC 4.8.3 and GCC 4.9.2. This is derived from log4cplus. The
test case is split into three files:

File def.hxx:

~~~~
#include <string>

namespace N
{
  struct S { std::string str; };
  // extern declaration in a header
  extern thread_local S * ptd;

  // accessing the extern declared ptd here
  inline
  S * get_ptd ()
  {
    if (! ptd)
      ptd = new S;
    return ptd;
  }
} // namespace N
~~~~

File def.cxx:

~~~~
#include "def.hxx"

namespace N
{
  // definition of ptd
  thread_local S * ptd = nullptr;
} // namespace N
~~~

File use.cxx:

~~~~
#include "def.hxx"

namespace N
{
  __declspec(dllexport)
  void * foo ()
  {
    // invoking inline get_ptd() function to get the value in ptd
    return get_ptd ();
  }
}
~~~~

Now, when I compile each .cxx with `g++ -std=gnu++11
-fvisibility=hidden -c use.cxx def.cxx` and then try to link with `g++
-shared -o cygtest.dll use.o def.o`, I get the following error from
linker:

~~~~
use.o:use.cxx:(.text$_ZTWN1N3ptdE[_ZTWN1N3ptdE]+0x15): relocation
truncated to fit: R_X86_64_PC32 against undefined symbol `TLS init
function for N::ptd'
collect2: error: ld returned 1 exit status
~~~~

The nm -C ./def.o output confirms that:

~~~~
`--> nm -C ./def.o
0000000000000000 b .bss
0000000000000000 d .data
0000000000000000 r .rdata
0000000000000000 r .rdata$zzz
0000000000000000 t .text
0000000000000008 r __emutls_t._ZN1N3ptdE
0000000000000000 D __emutls_v._ZN1N3ptdE
0000000000000000 r std::piecewise_construct
~~~~

As you can see, the ptd thread-local variable initialization function
is not defined anywhere. The use.o references this initialization
function (see bottom of the listing):

~~~~
`--> nm -C ./use.o
0000000000000000 b .bss
0000000000000000 d .data
0000000000000000 i .drectve
0000000000000000 p .pdata
0000000000000000 p .pdata$_ZN1N1SC1Ev
0000000000000000 p .pdata$_ZN1N7get_ptdEv
0000000000000000 p .pdata$_ZTWN1N3ptdE
0000000000000000 r .rdata
0000000000000000 r .rdata$.refptr.__emutls_v._ZN1N3ptdE
0000000000000000 r .rdata$.refptr._ZTHN1N3ptdE
0000000000000000 r .rdata$zzz
0000000000000000 R .refptr.__emutls_v._ZN1N3ptdE
0000000000000000 R .refptr._ZTHN1N3ptdE
0000000000000000 t .text
0000000000000000 t .text$_ZN1N1SC1Ev
0000000000000000 t .text$_ZN1N7get_ptdEv
0000000000000000 t .text$_ZTWN1N3ptdE
0000000000000000 A .weak._ZTHN1N3ptdE._ZN1N1SC1Ev
0000000000000000 r .xdata
0000000000000000 r .xdata$_ZN1N1SC1Ev
0000000000000000 r .xdata$_ZN1N7get_ptdEv
0000000000000000 r .xdata$_ZTWN1N3ptdE
                 U __emutls_get_address
                 U __emutls_v._ZN1N3ptdE
                 U __gxx_personality_seh0
                 U __real__ZdlPv
                 U __real__Znwm
                 U _Unwind_Resume
                 U operator delete(void*)
0000000000000000 T N::S::S()
0000000000000000 T N::foo()
0000000000000000 T N::get_ptd()
                 U std::basic_string<char, std::char_traits<char>,
std::allocator<char> >::basic_string()
                 U operator new(unsigned long)
0000000000000000 r std::piecewise_construct
                 w TLS init function for N::ptd
0000000000000000 T TLS wrapper function for N::ptd
~~~~

Now, this code seems to work well on Linux with both GCC and Clang.

Is this a GCC problem on Cygwin?
Am I using extern thread_local wrong?

My experiments show that not using the extern keyword seems to fix the
issue. But I am not sure if that does not introduce two ptd
thread-local variables in two TUs.

See also http://stackoverflow.com/q/28023728/341065

[Bug c++/64697] C++11 thread_local: relocation truncated to fit: R_X86_64_PC32 against undefined symbol `TLS init function for N::ptd'

[vhaisman at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64697

--- Comment #2 from Václav Zeman <vhaisman at gmail dot com> ---
Created attachment 34504
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def.cxx
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Subject: [Bug c++/64697] C++11 thread_local: relocation truncated to fit: R_X86_64_PC32 against undefined symbol `TLS init function for N::ptd'
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64697

--- Comment #1 from Václav Zeman <vhaisman at gmail dot com> ---
Created attachment 34503
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def.hxx
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Subject: [Bug c++/64697] C++11 thread_local: relocation truncated to fit: R_X86_64_PC32 against undefined symbol `TLS init function for N::ptd'
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64697

--- Comment #3 from Václav Zeman <vhaisman at gmail dot com> ---
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use.cxx
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https://gcc.gnu.org/bugzilla/show_bug.cgi?idd669

--- Comment #10 from Jiong Wang <jiwang at gcc dot gnu.org> ---
(In reply to Richard Henderson from comment #8)
> Indeed, if I force used_in_cond_stmt_p to return false, which forces
> the use of the emit_cstore path, which means we return a proper
> boolean value instead of a CCmode value, the test case doesn't ICE.
>
> Moreover, combine does in fact remove the redundant compare and we
> are left with
>
>         cmp     w0, 39
>         ccmp    w0, 10, 4, ne
>         bne     .L19
>
> I think I was wrong to approve the ccmp patch with the used_in_cond_stmt_p
> logic in the first place, and that it should all be removed.

Richard, will you send out the patch? I could help testing

[Bug c++/64697] C++11 thread_local: relocation truncated to fit: R_X86_64_PC32 against undefined symbol `TLS init function for N::ptd'

[wilson at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64697

Jim Wilson <wilson at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |wilson at gcc dot gnu.org

--- Comment #22 from Jim Wilson <wilson at gcc dot gnu.org> ---
This looks like a binutils bug to me.  A call to an undefined weak function
should never be executed, so it is OK for the linker to convert that call
instruction into anything convenient.  There is no need for a relocation that
can reach an address of zero.  We can convert the call instruction to call
itself, or the next instruction, or change it to a nop, what ever is
convenient, it doesn't really matter.

A number of binutils ports already have code to handle related problems.  ARM
and RISC-V for sure.  Probably others.  It looks like this support is missing
from the x86_64 port.  I'd suggest refiling this as a binutils bug.  See for
instance
  https://sourceware.org/bugzilla/show_bug.cgi?id=23244
for a RISC-V example of the same problem.  But we need a new bug for the x86_64
problem.  RISC-V has a register hard wired to zero, so I rewrite the call
instruction to use x0 as the base address.  The arm port turns the call into a
nop.

[Bug c++/64697] C++11 thread_local: relocation truncated to fit: R_X86_64_PC32 against undefined symbol `TLS init function for N::ptd'

[vhaisman at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64697

--- Comment #23 from Václav Haisman <vhaisman at gmail dot com> ---
I am not sure what to report. I do not understand the background of linker and
relocations enough. Also, I don't have access to Windows and Cygwin any more.

[Bug c++/64697] C++11 thread_local: relocation truncated to fit: R_X86_64_PC32 against undefined symbol `TLS init function for N::ptd'

[wilson at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64697

--- Comment #24 from Jim Wilson <wilson at gcc dot gnu.org> ---
Joel Sherrill offered to create a binutils bug report for this.

[Bug c++/64697] C++11 thread_local: relocation truncated to fit: R_X86_64_PC32 against undefined symbol `TLS init function for N::ptd'

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64697

--- Comment #25 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Eric Botcazou <ebotcazou@gcc.gnu.org>:

https://gcc.gnu.org/g:021ad8e5cf9ab66e1a0a41dce3a54586facb86e0

commit r12-4036-g021ad8e5cf9ab66e1a0a41dce3a54586facb86e0
Author: Eric Botcazou <ebotcazou@adacore.com>
Date:   Fri Oct 1 10:49:34 2021 +0200

    Fix PR c++/64697 at -O1 or above

    The BFD fix eliminates the link failure and working code is generated at
    -O0, but _not_ when optimization is enabled because the optimizer changes:

            movq    .refptr._ZTH1s(%rip), %rax
            testq   %rax, %rax
            je      .L2
            call    _ZTH1s

    into:

            leaq    _ZTH1s(%rip), %rax
            testq   %rax, %rax
            je      .L2
            call    _ZTH1s

    and the leaq now also gets the relocation overflow.  So the fix is to
    teach legitimate_pic_address_disp_p to reject the transformation when
    the symbol is an external weak function, which yields:

            cmpq    $0, .refptr._ZTH1s(%rip)
            je      .L2
            call    _ZTH1s

    and the cmpq keeps a relocation that does not overflow.

    gcc/
            PR c++/64697
            * config/i386/i386.c (legitimate_pic_address_disp_p): For PE-COFF
do
            not return true for external weak function symbols in medium model.

[Bug c++/64697] C++11 thread_local: relocation truncated to fit: R_X86_64_PC32 against undefined symbol `TLS init function for N::ptd'

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64697

--- Comment #26 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-11 branch has been updated by Eric Botcazou
<ebotcazou@gcc.gnu.org>:

https://gcc.gnu.org/g:618b7cb3b3fb4d2d92434d31ea8b6746ffef2572

commit r11-9049-g618b7cb3b3fb4d2d92434d31ea8b6746ffef2572
Author: Eric Botcazou <ebotcazou@adacore.com>
Date:   Fri Oct 1 10:49:34 2021 +0200

    Fix PR c++/64697 at -O1 or above

    The BFD fix eliminates the link failure and working code is generated at
    -O0, but _not_ when optimization is enabled because the optimizer changes:

            movq    .refptr._ZTH1s(%rip), %rax
            testq   %rax, %rax
            je      .L2
            call    _ZTH1s

    into:

            leaq    _ZTH1s(%rip), %rax
            testq   %rax, %rax
            je      .L2
            call    _ZTH1s

    and the leaq now also gets the relocation overflow.  So the fix is to
    teach legitimate_pic_address_disp_p to reject the transformation when
    the symbol is an external weak function, which yields:

            cmpq    $0, .refptr._ZTH1s(%rip)
            je      .L2
            call    _ZTH1s

    and the cmpq keeps a relocation that does not overflow.

    gcc/
            PR c++/64697
            * config/i386/i386.c (legitimate_pic_address_disp_p): For PE-COFF
do
            not return true for external weak function symbols in medium model.

[Bug c++/64697] C++11 thread_local: relocation truncated to fit: R_X86_64_PC32 against undefined symbol `TLS init function for N::ptd'

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64697

--- Comment #27 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-10 branch has been updated by Eric Botcazou
<ebotcazou@gcc.gnu.org>:

https://gcc.gnu.org/g:48e24ff39b16c072cd58bdad1a5668794453af5f

commit r10-10158-g48e24ff39b16c072cd58bdad1a5668794453af5f
Author: Eric Botcazou <ebotcazou@adacore.com>
Date:   Fri Oct 1 10:49:34 2021 +0200

    Fix PR c++/64697 at -O1 or above

    The BFD fix eliminates the link failure and working code is generated at
    -O0, but _not_ when optimization is enabled because the optimizer changes:

            movq    .refptr._ZTH1s(%rip), %rax
            testq   %rax, %rax
            je      .L2
            call    _ZTH1s

    into:

            leaq    _ZTH1s(%rip), %rax
            testq   %rax, %rax
            je      .L2
            call    _ZTH1s

    and the leaq now also gets the relocation overflow.  So the fix is to
    teach legitimate_pic_address_disp_p to reject the transformation when
    the symbol is an external weak function, which yields:

            cmpq    $0, .refptr._ZTH1s(%rip)
            je      .L2
            call    _ZTH1s

    and the cmpq keeps a relocation that does not overflow.

    gcc/
            PR c++/64697
            * config/i386/i386.c (legitimate_pic_address_disp_p): For PE-COFF
do
            not return true for external weak function symbols in medium model.

[Bug c++/64697] C++11 thread_local: relocation truncated to fit: R_X86_64_PC32 against undefined symbol `TLS init function for N::ptd'

[ebotcazou at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64697

Eric Botcazou <ebotcazou at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |FIXED
             Status|NEW                         |RESOLVED
   Target Milestone|---                         |10.4
                 CC|                            |ebotcazou at gcc dot gnu.org

--- Comment #28 from Eric Botcazou <ebotcazou at gcc dot gnu.org> ---
The binutils bug has been fixed in 2.36 or later:
  https://sourceware.org/bugzilla/show_bug.cgi?id=26659

The optimization bug will be fixed in upcoming 10.x, 11.x and 12.x releases.

[Bug c++/64697] C++11 thread_local: relocation truncated to fit: R_X86_64_PC32 against undefined symbol `TLS init function for N::ptd'

[ebotcazou at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64697

Eric Botcazou <ebotcazou at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |alvinhochun at gmail dot com

--- Comment #29 from Eric Botcazou <ebotcazou at gcc dot gnu.org> ---
*** Bug 104862 has been marked as a duplicate of this bug. ***