方法1.

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.

方法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 hostsomething 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

转自http://stackoverflow.com/questions/11535844/failed-to-attach-to-process-id-xcode

Failed to Attach to Process ID Xcode 解决办法,布布扣,bubuko.com