Leak when repeatedly loading and unloading plugin bundle

[edwloef]

Version

26.02

Plugin type

CLAP

OS

Linux

DAW / Host (if applicable)

any

Description

When repeatedly loading, initializing, deinitializing and unloading the Cardinal CLAP plugin bundle, each iteration leaves roughly 10MB of memory leaked. Heap profiling a debug build points at this call stack being the culprit:

Presumably, something isn't being properly deinitialized before the bundle is unloaded, and therefore stays present even after the bundle is unloaded?

The DPF implementation of clap_plugin_entry_deinit seems suspicious to me in this context, but I'm unfamiliar with what a ScopedPointer is so that might be an incorrect call:
https://github.com/DISTRHO/DPF/blob/main/distrho/src/DistrhoPluginCLAP.cpp#L2657-L2660

[falkTX]

In what host do you experience this issue?

Does clap_plugin_entry_deinit get called correctly?

On DPF side, the ScopedPointer behaves alike the "new" std::unique_ptr but for older versions of C++, that being C++98

[edwloef]

Here's a simple host to reproduce the issue:

#include "clap/include/clap/entry.h"
#include <dlfcn.h>
#include <unistd.h>

int main(int argc, char **argv) {
  if (argc != 2) {
    return 1;
  }

  const char *path = argv[1];

  for (;;) {
    void *handle = dlopen(path, RTLD_NOW | RTLD_LOCAL);
    if (dlerror() != NULL || handle == NULL) {
      return 1;
    }

    const clap_plugin_entry_t *entry = dlsym(handle, "clap_entry");
    if (dlerror() != NULL || entry == NULL) {
      dlclose(handle);
      return 1;
    }

    if (!entry->init(path)) {
      dlclose(handle);
      return 1;
    }

    entry->deinit();

    if (dlclose(handle) != 0) {
      return 1;
    }

    usleep(1000000);
  }

  return 0;
}

Supply the path to Cardinal.clap as the first program argument.

[edwloef]

Interestingly, moving the dlopen/dlclose out of the loop doesn't fix it, so the deinit doesn't leave anything initialized that a subsequent init can then know to skip initializing:

#include "clap/include/clap/entry.h"
#include <dlfcn.h>
#include <unistd.h>

int main(int argc, char **argv) {
  if (argc != 2) {
    return 1;
  }

  const char *path = argv[1];

  void *handle = dlopen(path, RTLD_NOW | RTLD_LOCAL);
  if (dlerror() != NULL || handle == NULL) {
    return 1;
  }

  const clap_plugin_entry_t *entry = dlsym(handle, "clap_entry");
  if (dlerror() != NULL || entry == NULL) {
    dlclose(handle);
    return 1;
  }

  for (;;) {
    if (!entry->init(path)) {
      dlclose(handle);
      return 1;
    }

    entry->deinit();

    usleep(1000000);
  }

  if (dlclose(handle) != 0) {
    return 1;
  }

  return 0;
}

[edwloef]

Maybe the leak is due to this static variable in the WSTD-Drums module set never being cleared: https://github.com/Wasted-Audio/WSTD-Drums/blob/main/src/WSTD_Drums.cpp#L9. there is setupSamples() but not teardownSamples() or something similar.