Fix plugin host watchdog treating zombies as alive

CHANGELOG.md

@@ -44,6 +44,10 @@ Versioning](https://semver.org/spec/v2.0.0.html).
   tries to use REAPER's [host function
   API](https://www.reaper.fm/sdk/vst/vst_ext.php#vst_host) which currently isn't
   supported by yabridge. We now explicitly ignore these requests.
+- Fixed the plugin-side watchdog timer that checks whether the Wine plugin host
+  process failed to start treating zombie processes as still running. This could
+  cause plugins to hang during scanning if the Wine process crashed in a very
+  specific (and likely impossible) way.
 - Fixed VST2 speaker arrangement configurations returned by the plugin not being
   serialized correctly. No plugins seem to actually use these, so it should not
   have caused any issues.

src/plugin/host-process.cpp

@@ -96,11 +96,10 @@ fs::path IndividualHost::path() {
     return host_path;
 }
 
-bool IndividualHost::running() noexcept {
-    std::error_code error{};
-    const bool running = host.running(error);
-
-    return running && !error;
+bool IndividualHost::running() {
+    // NOTE: `boost::process::child::running()` still considers zombies as
+    //       running, so it's useless for our purposes.
+    return pid_running(host.id());
 }
 
 void IndividualHost::terminate() {

src/plugin/host-process.h

@@ -52,7 +52,7 @@ class HostProcess {
      * Return true if the host process is still running. Used during startup to
      * abort connecting to sockets if the Wine process has crashed.
      */
-    virtual bool running() noexcept = 0;
+    virtual bool running() = 0;
 
     /**
      * Kill the process or cause the plugin that's being hosted to exit.
@@ -200,7 +200,7 @@ class IndividualHost : public HostProcess {
                    const HostRequest& host_request);
 
     boost::filesystem::path path() override;
-    bool running() noexcept override;
+    bool running() override;
     void terminate() override;
 
    private: