SEGV_MAPERR or SIGSEGV
segmentation fault， 一般由a dangling pointer issue, or some sort of buffer overflow
有两种SEGV，由一次无效内存访问错误引起。
1，A page was accessed which had the wrong permissions. 如某块内存区域是只读的，而程序尝试去写该块内存。SEGV_ACCERR
2，A page was accessed that is not even mapped into the address space of the application at all.
一般会dereferencing a null pointer or a pointer that was corrupted with a small integer value
SEGV_MAPERR
