问题
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?
回答1:
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.
回答2:
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.
回答3:
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.
来源：https://stackoverflow.com/questions/19119943/what-does-segv-accerr-mean