Re: Base libc++ missing symbol

On Oct 2, 2023, at 15:56, Mark Millard <marklmi@yahoo.com> wrote:

> Joel Bodenmann <jbo_at_FreeBSD.org> wrote on
> Date: Mon, 02 Oct 2023 20:00:29 UTC :
> 
>> It seems like I finally managed to hose a FreeBSD system.
>> The machine in question is my workstation at home. It has been running
>> stable/13 without any problems. Yesterday I've updated to
>> ef295f69abbffb3447771a30df6906ca56a5d0c0 and since then I'm getting an
>> undefined symbol on anything using Qt:
>> 
>> ld-elf.so.1: /usr/local/lib/qt5/libQt5Widgets.so.5: Undefined symbol
>> "_ZTVNSt3__13pmr25monotonic_buffer_resourceE"
>> 
>> Unless I'm missing something, it would seem like my base libc++
>> is missing the pmr::monotonic_buffer_resource symbol.
> 
> I do not have a 13.2 context, so you may want to run the
> analogous steps in your context for confirming/denying
> the below applies.
> 
> # llvm-cxxfilt _ZTVNSt3__13pmr25monotonic_buffer_resourceE
> vtable for std::__1::pmr::monotonic_buffer_resource
> 
> Using the example "Run this code" source from:
> 
> https://en.cppreference.com/w/cpp/memory/monotonic_buffer_resource
> 
> # c++ -std=c++17 -pedantic -O2 monotonic_buffer_resource.cpp
> 
> # objdump -x a.out | grep _ZTVNSt3__13pmr25monotonic_buffer_resourceE
> 0000000000204160 g     O .bss.rel.ro 0000000000000038 _ZTVNSt3__13pmr25monotonic_buffer_resourceE
> 
> # nm a.out | grep _ZTVNSt3__13pmr25monotonic_buffer_resourceE
> 0000000000204160 B _ZTVNSt3__13pmr25monotonic_buffer_resourceE
> 
> # ./a.out
> t1 (default std alloc): 0.491 sec; t1/t1: 1.000
> t2 (default pmr alloc): 0.541 sec; t1/t2: 0.906
> t3 (pmr alloc  no buf): 0.188 sec; t1/t3: 2.616
> t4 (pmr alloc and buf): 0.155 sec; t1/t4: 3.172
> 
> Note that the vtable is in the a.out instead of being from
> a library. It is global but is in the a.out .bss.rel.ro <http://bss.rel.ro/> in
> the example and is defined.
> 
>> At first I thought I might have messed up on installworld but rolling
>> back to the previous boot environment and then performing the same
>> procedure again lead to the same outcome.
> 
> If the above works similarly in your context, then I expect
> that the issue is on the qt5 or port side of things, not the
> system libraries/headers.
> 
> As I understand, clang++ 16 is the first vintage with this
> directly supported, instead of being just in the experimental
> category/area for libc++. May be tracking that transition is
> at issue.
> 
> For reference:
> 
> # c++ -v
> FreeBSD clang version 16.0.6 (https://github.com/llvm/llvm-project.git llvmorg-16.0.6-0-g7cbf1a259152)
> Target: x86_64-unknown-freebsd15.0
> Thread model: posix
> InstalledDir: /usr/bin
> 
> # uname -apKU
> FreeBSD amd64-ZFS 15.0-CURRENT FreeBSD 15.0-CURRENT #124 main-n265447-e5236d25f2c0-dirty: Thu Sep 21 09:06:08 PDT 2023     root@amd64-ZFS:/usr/obj/BUILDs/main-amd64-nodbg-clang/usr/main-src/amd64.amd64/sys/GENERIC-NODBG amd64 amd64 1500001 1500001
> 
>> Any ideas or wild guesses? Anything obvious I'm missing here?
>> 
>> uname -a
>> FreeBSD beefy02 13.2-STABLE FreeBSD 13.2-STABLE
>> stable/13-n256443-ef295f69abbf GENERIC amd64
>> 
>> freebsd-version -kru
>> 13.2-STABLE
>> 13.2-STABLE
>> 13.2-STABLE
>> 
>> clang --version
>> FreeBSD clang version 16.0.6
>> (https://github.com/llvm/llvm-project.git
>> llvmorg-16.0.6-0-g7cbf1a259152) Target: x86_64-unknown-freebsd13.2
>> Thread model: posix
>> InstalledDir: /usr/bin
> 

Given Dimitry Andric's notes:

# objdump -x /lib/libc++.so.1 | grep _ZTVNSt3__13pmr25monotonic_buffer_resourceE
00000000001006d8 g     O .data.rel.ro 0000000000000038 _ZTVNSt3__13pmr25monotonic_buffer_resourceE

# nm /lib/libc++.so.1 | grep _ZTVNSt3__13pmr25monotonic_buffer_resourceE
00000000001006d8 D _ZTVNSt3__13pmr25monotonic_buffer_resourceE

So /lib/libc++.so.1 has a global symbol naming initialized data
for this in my context.

Reminder for the a.out:

# objdump -x a.out | grep _ZTVNSt3__13pmr25monotonic_buffer_resourceE
0000000000204160 g     O .bss.rel.ro 0000000000000038 _ZTVNSt3__13pmr25monotonic_buffer_resourceE

# nm a.out | grep _ZTVNSt3__13pmr25monotonic_buffer_resourceE
0000000000204160 B _ZTVNSt3__13pmr25monotonic_buffer_resourceE

My original thinking makes no sense for this. Sorry for the noise.

The procedure of seeing if the a.out is produced without complaint
might still be useful.

===
Mark Millard
marklmi at yahoo.com