Is your app sandboxed? Yes, it is sandboxed.

Thanks eskimo, The semaphore & shared memory issue has been solved. Could I ask one more related question in this thread? The app is sandboxed in this situation. I use posix_spawn to open another instance of the same application. I get the pid successfully, but i could not find the Window. It works when it is a non-sandboxed app. Find nothing about this in the page IPC and POSIX Semaphores and Shared Memory - https://developer.apple.com/library/archive/documentation/Security/Conceptual/AppSandboxDesignGuide/AppSandboxInDepth/AppSandboxInDepth.html#//apple_ref/doc/uid/TP40011183-CH3-SW24 Thanks again gracefully.

When then user click button on the window, it would trigger posix_spawn(&pid, argv[0], NULL, NULL, argv, env) to start another process of the same program. In sandbox situation. The triggered window did not show up. Best Regards

Yeeees, totally correct. Best Regards

Hi eskimo, The system attaches entitlements to a process when it execs, so a simple fork doesn’t trigger this issue. A posix_spawn is (by default) a fork/exec, and it’s the exec that’s causing you problems. macOS and Linux have very different architectures when it comes to GUI process management. Thanks for your explaination. I think this thread could be closed. Our target is to make the app one-progress-multiple-window. We use flutter, but it does not support this feature currently. So we must find the workaround. Best Regards

Thanks Eskimo, I am working on a cross-platform infra project. We try to follow things we have done under linux. One more details I forget to mention. When the app is sandboxed, I can do the same thing using fork(). Table - https://developer.apple.com/forums/content/attachment/25fad295-0b00-472c-b6d6-e5bfbc44e5f1 Thanks again.