LSP Plugins 1.2.23 released!

axra · September 8, 2025, 6:14am

Yes I can confirm this issue. I’m on CachyOS. Same issue with ZynAddSubFx LV2. VST working.
https://tracker.ardour.org/view.php?id=10003
But the issue only occurs in Ardour, no issues in Reaper or Qtractor.

SadKo · September 8, 2025, 8:50am

@werner.back @axra Is is possible for you to obtain the stack trace of Ardour? It may be very helpful.

werner.back · September 8, 2025, 11:10am

How do I do that? I just get the message “segmentation fault (core dumped)”, but where is the dump?

x42 · September 8, 2025, 11:20am

They also say that about VST3

x42 · September 8, 2025, 11:23am

cat /proc/sys/kernel/core_pattern

Usually a file called core in the current working directory, but some distros set a dedicated path or redirect it.

Note that the core file only applies to your system. You then have to load it into gdb to get a backtrace: see Debugging Ardour | Ardour DAW

I find it much easier to directly run Ardour in gdb instead.

werner.back · September 8, 2025, 12:28pm

Selfcompiled Version of both Ardour(8.12 from git) and LSP (current git). I created 2 Tracks and put a parametric EQ on each of them. Opened the first one and made some adjustment and closed it. Then I opened the second EQ, the window appears, but then the crash happens.

Output fom gdb is here:
File

x42 · September 8, 2025, 12:41pm

So …

#0  __strstr_sse2_unaligned () at ../sysdeps/x86_64/multiarch/strstr-sse2-unaligned.S:41
#1  0x00007fff4b102144 in lsp::ws::glx::check_gl_extension(char const*, char const*) () from /home/werner/.lv2/lsp-plugins.lv2/lsp-plugins-lv2ui.so
#2  0x0000000000000000 in ?? ()

@SadKo could it be that unloading the UI (lsp-plugins-lv2ui.so) causes it? Is there static init happening? That would explain why the VST3 is not affected.

SadKo · September 8, 2025, 2:51pm

The check of OpenGL extensions is performed at the start of UI when we’re creating OpenGL context of the window. The verification routine is the following:

github.com

lsp-plugins/lsp-ws-lib/blob/e8807b3eab20a283415ae9cb03b0cbb81b576080/src/main/glx/Context.cpp#L80-L96


      
          static bool check_gl_extension(const char *list, const char *check)
          {
              const size_t len = strlen(check);
          
          
    while (true)
              {
                  const char *item = strstr(list, check);
                  if (item == NULL)
                      return false;
                  if ((item == list) || (item[-1] == ' '))
                  {
                      if ((item[len] == ' ') || (item[len] == '\0'))
                          return true;
                  }
                  list = &item[len];
              }
          }

I need the OpenGL string to perform the test.
@werner.back could you please build plugins with make config ... TRACE=1 option and uncomment this line:

github.com

lsp-plugins/lsp-ws-lib/blob/e8807b3eab20a283415ae9cb03b0cbb81b576080/include/private/gl/defs.h#L49


      
                  #include <GL/glext.h>
              #endif
          #endif /* LSP_PLUGINS_USE_OPENGL_GLX */
          
          
// Enable overall OpenGL
          #if defined(LSP_PLUGINS_USE_OPENGL_GLX)
              #define LSP_PLUGINS_USE_OPENGL
          #endif /* LSP_PLUGINS_USE_OPENGL_GLX */
          
          
// Uncomment this to log all OpenGL object allocations and deletions
          //#define TRACE_OPENGL_ALLOCATIONS
          
          
// Uncomment this to log all OpenGL statistics
          //#define TRACE_OPENGL_STATS
          
          
#ifdef TRACE_OPENGL_ALLOCATIONS
              #define IF_TRACE_OPENGL_ALLOCATIONS(...) __VA_ARGS__
              #define lsp_gl_trace(...) lsp_trace(__VA_ARGS__)
          #else
              #define IF_TRACE_OPENGL_ALLOCATIONS(...)
              #define lsp_gl_trace(...) LSP_DEBUG_STUB_CALL

In the log of LV2 plugins you will see the output of this command:

github.com

lsp-plugins/lsp-ws-lib/blob/e8807b3eab20a283415ae9cb03b0cbb81b576080/src/main/glx/Context.cpp#L609


      
              return features;
          }
          
          
static uint32_t detect_features(glx::vtbl_t *vtbl)
          {
              uint32_t features   = Context::NO_FEATURES;
          
          
    const char *extensions = reinterpret_cast<const char *>(vtbl->glGetString(GL_EXTENSIONS));
              if (extensions != NULL)
              {
                  lsp_gl_trace("OpenGL extensions: %s", extensions);
                  features               |= test_features(extensions);
              }
          
          
    lsp_gl_trace("OpenGL extensions: %s", extensions);
          
          
    GLint num_extensions = 0;
              vtbl->glGetIntegerv(GL_NUM_EXTENSIONS, &num_extensions);
              for (GLint i = 0; i<num_extensions; ++i)
              {
                  extensions              = reinterpret_cast<const char *>(vtbl->glGetStringi(GL_EXTENSIONS, i));

werner.back · September 8, 2025, 5:04pm

Compiling atm…but where do I find the log?

SadKo · September 8, 2025, 5:16pm

The log is written into /tmp/lsp-lv2ui.log.

werner.back · September 8, 2025, 5:21pm

Thanks, got it.
lsp_lv2ui.log
lsp-lv2.log

SadKo · September 8, 2025, 5:38pm

Looks like second call of the glXQueryExtensionsString call returns NULL on your system. That’s strange and looks like a driver bug. Do you use XWayland or pure X11?
Please consider applying this patch:

werner.back · September 8, 2025, 7:19pm

I tried both (at login chose plasma-X11, also tried plasma-Wayland). With the patch applied, everything seems to work fine again, though.
Thank you very, very much!

SadKo · September 8, 2025, 7:55pm

I also need to ask you to check that plugins do not fall-back to Cairo.
You can see the rendering subsystem used in the About dialog.

werner.back · September 9, 2025, 2:47am

It says openGL Thanks again.
Bildschirmfoto_20250909_044541

Schmitty2005 · September 9, 2025, 3:39am

Your screenshot shows Cairo

werner.back · September 9, 2025, 3:52am

Aah, ok. I did’t look close when I made the screenshot. At the first call it shows openGL, but at the second call it shows Cairo. I didn’t notice that.

SadKo · September 9, 2025, 8:01am

That’s bad. Seems that I need to remember the result of the first call of glXQueryExtensionsString because it badly behaves on your system. An upstream bug of x11?

SadKo · September 9, 2025, 9:11pm

@werner.back I added some code to cache the result of glXQueryExtensionString here:

Please check that you don’t fall-back to Cairo with this patch.

werner.back · September 10, 2025, 11:42am

I’m really confused now. Because I don’t know how to apply those changes to my source tree I simply checked out the whole devel branch and installed it. The good thing is that it stays on openGL now. The bad thing is that I got random crashes all over the place. I could open plugins a few times without an issue, but then suddenly I get segfaults. So I installed master again (the one I compiled yesterday, I just copied the files). Surprisingly now this version ALSO stays in openGL! I don’t know, what I’m supposed to do now…it seems now things are working, but no one knows why