I am examining a few crashes that all have the signal SIGSEGV with the reason SEGV_ACCERR. After searching for SEGV_ACCERR, the closest thing I have found to a human readable explanation is: Invalid Permissions for object
What does this mean in a more general sense? When would a SEGV_ACCERR arise? Is there more specific documentation on this reason?
This is an error that I have mostly seen on 64 bit iOS devices and can happen if multiple threads read and change a variable under ARC. For example, I fixed a crash today where multiple background threads were reading and using a static NSDate and NSString variable and updating them without doing any kind of locking or queueing.
Using core data objects on multiple threads can also cause this crash, as I have seen many times in my crash logs.
I also use Crittercism, and this particular crash was a SEGV_ACCERR that only affected 64 bit devices.
As stated in the man page of sigaction, SEGV_ACCERR is a signal code for SIGSEGV that specifies Invalid permissions for mapped object. Contrary to SEGV_MAPERR which means that the address is not mapped to a valid object, SEGV_ACCERR means the address matches an object, but for sure it is neither the good one, nor one the process is allowed to access.
I've seen this in cases where code tries to execute from places other than "text".
For eg, if your pointer is pointing to a function in heap or stack and you try to execute that code (from heap or stack), the CPU throws this exception.
来源：https://stackoverflow.com/questions/19119943/what-does-segv-accerr-mean