Xcode 9: Could not attach to pid

Question

I've been facing an issue (frequently) with the recent major release of the iOS application development tool - Xcode 9-beta.

It's showing me the following error frequently while running/debugging app in Simulator (iOS 11).

Could not attach to pid : “2370”
Ensure <project title> is not already running, and <system username> has permission to debug it.

Here is a snapshot for the same issue:

What would be permanent solution of this issue, as it's disturbing frequently?

Answer 1

(most likely solution) 1. Simulator-> Hardware-> Erase all contents and Settings

(less likely solution) 2. keychain-> upper right lock-> unlock and lock again (or the other way around)

Answer 2

Still not a permanent solution, but I had to quit and restart XCode as the other solutions did not work for me.

Answer 3

delete derived data and clean the project, wait until processing is complete, this may take some time. The idea is to give some processing time. Works fine after that

Answer 4

I hate to add more noise to this, but for me, the answer is to, nonsensically, use sudo.

Run normally, Xcode 9.4.1 (9F2000) and Xcode 10.0 beta 4 (10L213o) both failed to attach to my app after multiple tries, giving the error quoted in the original post.

What worked was to run Xcode (9.4) with sudo,

sudo /Applications/Xcode.app/Contents/MacOS/Xcode

I don't see why sudo is necessary. The Cocoa app to which I am attaching is a Debug build that I just built in Xcode 9.4.1 and dragged into /Applications. It is not codesigned. Posix permissions on the .app, its Contents, its MacOS, and the executable are all octal 755. Owner is me. It works fine if I leave it in the Build folder, build and debug in the normal way.

The problem is apparently with lldb. I also tried using lldb (lldb-902.0.79.7) from the command line. I got the same result. It works only with sudo. Without sudo,

error: attach failed: unable to attach

Answer 5

Killing my simulator and then running it again from Xcode.

Answer 6

This seems to be a temporary issue when you are trying to build too fast after a build has started. Try stopping and running the project again.