When I run the app in Xcode IOS 6 beta 2 firmware on the device 8 Beta 2, I get the error message: "dyld: could not load inserted library '/ USR / Library / libgmalloc.dylib", because the image was not found. "
What could be the problem?
Disable "Enable guard Malloc" from diagnostics to run app in device.
This is because Xcode mount wrong DeveloperImage. If you open the Settings-> Developer you will see that the "Enable UIAutomation» and others are missing.
For fix:
- move all folders from "/Applications/Xcode6-Beta2.app/Contents/Developer/Platforms/iPhoneOS.platform/DeviceSupport" except "8.0 (12A4297e)" to safe place
- reboot the phone
- connect your phone to xCode 6 beta 2
- restore folders in DeviceSupport
This is the only thing that helped me. Even re-flashing on ios8 beta2 does not helps.
If you're using any 3rd party IDEs for iOS development (e.g. RubyMotion) you should be able to fix this by rebooting your device without that 3rd party IDE running and building and running an app on your device from Xcode.
I've been seeing this on Xcode 7.1. My quick and dirty solution has been to open the right sidebar of the playground, and toggle the platform setting under "Playground Settings".
In my case, I toggled from iOS to OS X and viola, playground compiles and runs as expected.
Reboots had no effect in my case.
Just restart your iPhone. It worked for me.
Disable "Enable guard Malloc" from diagnostics to run app in device.
Edit Scheme
step - 1
Step 2: 
you can see Memory Management Uncheck Guard Malloc
Try deleting the app from the device and then reboot. Worked for me.
来源：https://stackoverflow.com/questions/24511663/dyld-could-not-load-inserted-library-usr-lib-libgmalloc-dylib-because-image