pangolin::X11Window::MakeCurrent segmentation fault when compiled with libtorch

[fwcore]

Hi @stevenlovegrove,

Thank you very much for this great work.

I met a problem when I tried to used Pangolin as GUI and libtorch as a deep-learning inference engine together.

I confirmed that

• using Pangolin alone has no problem
• using libtorch alone or libtorch+opengl has no problem
• using both libtorch + pangolin fails. It fails no matter whether compiling pangolin as a shared or static library, with or without -fvisibility=hidden.

Please see what I had tried in https://github.com/fwcore/pangolin-libtorch-issue/tree/main

Here is minimal example:

#include <pangolin/pangolin.h>
#include <torch/torch.h>

#include <iostream>

int main() {
  auto x = torch::zeros({2, 5});
  std::cout << x << std::endl;
  pangolin::CreateWindowAndBind("Viewer", 600, 600);

  glEnable(GL_DEPTH_TEST);

  pangolin::DestroyWindow("Viewer");
  pangolin::QuitAll();
  return 0;
}

Here is the detailed segmentation fault backtrace:

Pass 'Combine redundant instructions' is not initialized.                                                                                                                                                                                                                 
Verify if there is a pass dependency cycle.                                                                                                                                                                                                                             
Required Passes:                                                                                                                                            

Thread 1 "pangolin_libtor" received signal SIGSEGV, Segmentation fault.                                                                                                                                                                                                   
0x00007f77aa67b378 in llvm::PMTopLevelManager::schedulePass(llvm::Pass*) ()                                                                                                                                                                                             
   from /lib/x86_64-linux-gnu/libLLVM-12.so.1                                                                                                                                                                                                                           
(gdb) bt                                                                                                                    
#0  0x00007f77aa67b378 in llvm::PMTopLevelManager::schedulePass(llvm::Pass*) ()                                                                                                                                                                                         
   from /lib/x86_64-linux-gnu/libLLVM-12.so.1                                                                                                                                                                                                                           
#1  0x00007f77af98a0a7 in ?? () from /usr/lib/x86_64-linux-gnu/dri/swrast_dri.so                                                                                                                                                                                        
#2  0x00007f77af98a190 in ?? () from /usr/lib/x86_64-linux-gnu/dri/swrast_dri.so                                                                                                                                                                                        
#3  0x00007f77afa057b7 in ?? () from /usr/lib/x86_64-linux-gnu/dri/swrast_dri.so                                                                                                                                                                                        
#4  0x00007f77af9f7438 in ?? () from /usr/lib/x86_64-linux-gnu/dri/swrast_dri.so                                                                                                                                                                                        
#5  0x00007f77af9dd9d0 in ?? () from /usr/lib/x86_64-linux-gnu/dri/swrast_dri.so                                                                                                                                                                                        
#6  0x00007f77aff38bfd in ?? () from /usr/lib/x86_64-linux-gnu/dri/swrast_dri.so                                                                                                                                                                                        
#7  0x00007f77aff38f10 in ?? () from /usr/lib/x86_64-linux-gnu/dri/swrast_dri.so                                                                                                                                                                                        
#8  0x00007f77aff394b6 in ?? () from /usr/lib/x86_64-linux-gnu/dri/swrast_dri.so                                                                                                                                                                                        
#9  0x00007f77aff3c13c in ?? () from /usr/lib/x86_64-linux-gnu/dri/swrast_dri.so                                                                                                                                                                                        
#10 0x00007f77aff3cd72 in ?? () from /usr/lib/x86_64-linux-gnu/dri/swrast_dri.so                                                                                                                                                                                        
#11 0x00007f77afa0a837 in ?? () from /usr/lib/x86_64-linux-gnu/dri/swrast_dri.so                                                                                                                                                                                        
#12 0x00007f77af2eab43 in ?? () from /usr/lib/x86_64-linux-gnu/dri/swrast_dri.so                                                                                                                                                                                        
#13 0x00007f77af2e6081 in ?? () from /usr/lib/x86_64-linux-gnu/dri/swrast_dri.so                                                                                                                                                                                        
#14 0x00007f77af2eb02e in ?? () from /usr/lib/x86_64-linux-gnu/dri/swrast_dri.so                                                                                                                                                                                        
#15 0x00007f77af34771a in ?? () from /usr/lib/x86_64-linux-gnu/dri/swrast_dri.so                                                                                                                                                                                        
#16 0x00007f77af347a0a in ?? () from /usr/lib/x86_64-linux-gnu/dri/swrast_dri.so                                                                                                                                                                                        
#17 0x00007f77af2ea981 in ?? () from /usr/lib/x86_64-linux-gnu/dri/swrast_dri.so                                                                                                                                                                                        
#18 0x00007f77af8c8cea in ?? () from /usr/lib/x86_64-linux-gnu/dri/swrast_dri.so                                                                                                                                                                                        
#19 0x00007f77b4871656 in ?? () from /lib/x86_64-linux-gnu/libGLX_mesa.so.0                                                                                                                                                                                             
#20 0x00007f77b48762be in ?? () from /lib/x86_64-linux-gnu/libGLX_mesa.so.0                                                                                                                                                                                             
#21 0x00007f783e9b0e93 in ?? () from /lib/x86_64-linux-gnu/libGLX.so.0                                                                                                                                                                                                  
#22 0x00007f783e9b1467 in ?? () from /lib/x86_64-linux-gnu/libGLX.so.0                                                                                                                                                                                                  
#23 0x00007f783e9b2c58 in ?? () from /lib/x86_64-linux-gnu/libGLX.so.0                                                                                                                                                                                                  
#24 0x00007f7844c80ac1 in pangolin::X11Window::MakeCurrent(__GLXcontextRec*) ()                                                                                                                                                                                         
   from /workspace/install2/lib/libpangolin.so                                                                                                                                                                                                                     
#25 0x00007f7844c80f7d in pangolin::X11Window::MakeCurrent() ()                                                                                                                                                                                                         
   from /workspace/install2/lib/libpangolin.so                                                                                                                                                                                                                     
#26 0x00007f7844bb9ea5 in pangolin::CreateWindowAndBind(std::__cxx11::basic_string<char,                                                                                                                                                                                std::char_traits<char>, std::allocator<char> >, int, int, pangolin::Params const&) ()                                                                                                                                                                                   
   from /workspace/install2/lib/libpangolin.so                                                                                                                                                                                                                     
#27 0x00000000004025a7 in main ()                                                                                                                                                                                               
--Type <RET> for more, q to quit, c to continue without paging--                                                                                                                                                                                                          
    at /workspace/pangolin_libtorch/pangolin_libtorch.cpp:9

My system:

• ubuntu 22.04
• libtorch 2.0.1: https://download.pytorch.org/libtorch/cu117/libtorch-cxx11-abi-shared-with-deps-2.0.1%2Bcu117.zip

$ glxinfo | grep OpenGL
OpenGL vendor string: Mesa/X.org
OpenGL renderer string: llvmpipe (LLVM 12.0.0, 256 bits)
OpenGL core profile version string: 4.5 (Core Profile) Mesa 21.2.6
OpenGL core profile shading language version string: 4.50
OpenGL core profile context flags: (none)
OpenGL core profile profile mask: core profile
OpenGL core profile extensions:
OpenGL version string: 3.1 Mesa 21.2.6
OpenGL shading language version string: 1.40
OpenGL context flags: (none)
OpenGL extensions:
OpenGL ES profile version string: OpenGL ES 3.2 Mesa 21.2.6
OpenGL ES profile shading language version string: OpenGL ES GLSL ES 3.20
OpenGL ES profile extensions:

I didn't find the root cause of the issue. I googled the error message, but didn't find anything useful except: horovod/horovod#3415. It seems like there are some symbol conflicts between Pangolin and libtorch, but I am not sure.

Could you please help me on that?

Thank you very much.

[fwcore]

Further study

Since the above error is related to GLX, I tried a branch of Pangolin which replaced GLX by EGL.

• This branch can compile and the example HelloPangolin works well.
• The example pangolin_libtorch_test gives

Thread 1 "pangolin_libtor" received signal SIGSEGV, Segmentation fault.
__GI___libc_free (mem=0x1) at malloc.c:3102
3102    malloc.c: No such file or directory.
(gdb) bt
#0  __GI___libc_free (mem=0x1) at malloc.c:3102
#1  0x00007f65aeadee69 in llvm::cl::Option::~Option() () from /workspace/build/_deps/torch-src/lib/libtorch_cpu.so
#2  0x00007f6562f8ffde in __cxa_finalize (d=0x7f65c08ec000) at cxa_finalize.c:83
#3  0x00007f65aa4c9d33 in __do_global_dtors_aux () from /workspace/build/_deps/torch-src/lib/libtorch_cpu.so
#4  0x00007ffec316a970 in ?? ()
#5  0x00007f65c92d3f6b in _dl_fini () at dl-fini.c:138
Backtrace stopped: frame did not save the PC

Clearly this error is on Pytorch's side. Both messages point to LLVM, indicating a symbol conflict.

After googling this message, more information is found:

• Qt + libtorch: libtorch > 1.9.1 produces segfault on Qt5 gui application exit pytorch/pytorch#103756
• Valkun + libtorch: Segfault when running vulkan program linked against libtorch pytorch/pytorch#102533
• SDL + libtorch: Segfault when using libtorch + sdl pytorch/pytorch#71283

Moreover, I find that opengl_libtorch_test also generates the same segfault (since the message is different from the previous one, I just ignored it yesterday).

In pytorch/pytorch#103756, a patch is provided just two weeks ago (pytorch/builder#1445). So I tried the nightly built version 2.1.0.dev20230724+cu118 (accessed on July 25, 2023), and found that it works for both Pangolin & OpenGL, and all above issues are gone.

So I closed this issue. Thank you very much.