Created attachment 625 [details]
Code to reproduce
attached code calling nonZeros() on a col() of a row-major sparse matrix segfaults with eigen 3.2.7 (same for row() of a column-major).
Indeed, the pb is that such a function does not exist (counting the number of non zeros of a row of a column major matrix is a O(n*log(nnz_per_col)) pb, so you don't want to do that). What current happens is that it starts an infinite recursion loop... This is already fixed in the devel branch (as a compilation error), and here is the fix for the 3.2 branch:
Summary: Bug 1111: fix infinite recursion in sparse-column-major.row(i).nonZeros() (it now produces a compilation error)