Failed to Attach to Process ID Xcode

Question

Resetting the content and settings in the simulator worked for me. This is available in the "iOS Simulator" menu.

go to the Product menu and find the Edit Scheme menu there.

While in Edit Scheme window, select the "Run" option on the left hand side of the screen and then on the right hand side, change the debugger from LLDB to GDB.

I experienced the same problem, and after a while I found out that it was due to the fact that my XCode project included a Folder Reference to a folder named Resources.

It seems that XCode doesn't like that name.

Just removing the folder reference or renaming the folder solved the issue.

TWO METHODS

Method 1 : Inside the folder Application Support -> iPhone Simulator -> In the each simulator version of iOS -> Applications -> Delete all the files present here.

Now go to Products -> Clean

Now run it on any simulator and it will work.

Method 2 :

Step1: ping

$ ping localhost

This should return something like

PING localhost (127.0.0.1): 56 data bytes
64 bytes from 127.0.0.1: icmp_seq=0 ttl=64 time=0.028 ms
64 bytes from 127.0.0.1: icmp_seq=1 ttl=64 time=0.048 ms
...

If this works, this answer won't fix your problem, try something else.

If ping return something else for example: ping: cannot resolve localhost: Unknown host something is screwed up with your /etc/hosts file, go to Step 2

Step2: Check /etc/hosts

Check that the top of your /etc/hosts file looks like this

127.0.0.1       localhost
255.255.255.255 broadcasthost
::1             localhost 
fe80::1%lo0     localhost

If it doesn't have these entries in the file, enter them at the top of the file, flush the dns cache using $ dscacheutil -flushcache and go back to Step 1, otherwise continue to Step 3.

Step3: Correct File Format: It should be unix or LF *

$ file /etc/hosts

This should return: /etc/hosts: ASCII English text

If it returns something like /etc/hosts: ASCII English text, with CR line terminators then the file is in the wrong format and is likely being ignored.

Change the file line endings to unix or LF using your favorite text editor.

• In Sublime Text 2 this can be done throught the view menue: View > Line Endings > Unix

Flush the dns cache ($ dscacheutil -flushcache) and go back to step 1

Similar to fundtimer's answer, the local hosts file seems to have been the culprit.

I had to change my /etc/hosts permissions back to the default after an inadvertent change:

sudo chmod 644 /etc/hosts

After that, simulator/LLDB worked for me.