Crystrix edited a comment on pull request #11789:
URL: https://github.com/apache/arrow/pull/11789#issuecomment-986262845


   > I see. I don't think we want to add such a file to the test suite, no.
   
   I have no idea to add a suitable test case. Here is an explanation of the 
reason why it is not easy to reproduce:
   
   In general, the occurrence of the crash depends on the allocation of memory.
   
   The `std::memcpy` always copies 8 bytes. So the out-of-bounds memory access 
happens if the source variable is less than 8 bytes. But if the accessed memory 
is still in the address space of the process, then the crash won't happen. And 
the invalid copied tailing bytes are filtered out by a mask, so the result is 
still correct.
   
   Only after reading a specific data file as a `MemoryMappedFile` and 
executing `GroupBy` with keys of a single char, the accessed memory won't be in 
the address space of the process. Then the OS will terminate the process with a 
segmentation fault.
   
   
   
   
   


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