Created attachment 1533 [details]
Small R-program triggering the overflow
The rowsum.default() for real matrices segfaults with matrices with more than 2^31 elements.
A fix is to declare offsetg and offset in rowsum() in src/main/unique.c as R_xlen_t
A similar problem may be present in rowsum_df(), but I have not looked at it.
This example worked for me, but code has been changed.