Fix #122973: Subprocesses aren't closed if Blender crashes

Assigns all subprocesses to a job owned by the main Blender instance,
so they're closed when it ends.

Pull Request: https://projects.blender.org/blender/blender/pulls/123001

source/blender/blenlib/intern/BLI_subprocess.cc

@@ -56,6 +56,34 @@ static void check(bool result, const char *function, const char *msg)
 #    undef ERROR /* Defined in wingdi.h */
 #    define ERROR(msg) check(false, __func__, msg)
 
+/* Owning process group that will close subprocesses assigned to it when the instance is destructed
+ * or the creator process ends. */
+class ProcessGroup {
+ private:
+  HANDLE handle_;
+
+ public:
+  ProcessGroup()
+  {
+    handle_ = CreateJobObject(nullptr, nullptr);
+    CHECK(handle_);
+    JOBOBJECT_EXTENDED_LIMIT_INFORMATION info = {0};
+    info.BasicLimitInformation.LimitFlags = JOB_OBJECT_LIMIT_KILL_ON_JOB_CLOSE;
+    CHECK(
+        SetInformationJobObject(handle_, JobObjectExtendedLimitInformation, &info, sizeof(info)));
+  }
+
+  ~ProcessGroup()
+  {
+    CHECK(CloseHandle(handle_));
+  }
+
+  void assign_subprocess(HANDLE subprocess)
+  {
+    CHECK(AssignProcessToJobObject(handle_, subprocess));
+  }
+};
+
 bool BlenderSubprocess::create(Span<StringRefNull> args)
 {
   BLI_assert(handle_ == nullptr);
@@ -91,7 +119,7 @@ bool BlenderSubprocess::create(Span<StringRefNull> args)
                       nullptr,
                       nullptr,
                       false,
-                      0,
+                      CREATE_BREAKAWAY_FROM_JOB,
                       nullptr,
                       nullptr,
                       &startup_info,
@@ -104,6 +132,10 @@ bool BlenderSubprocess::create(Span<StringRefNull> args)
   handle_ = process_info.hProcess;
   CHECK(CloseHandle(process_info.hThread));
 
+  static ProcessGroup group;
+  /* Don't let the subprocess outlive its parent. */
+  group.assign_subprocess(handle_);
+
   return true;
 }