The attached patch is needed to make cscope build on Gentoo/*BSD systems, it replaces a generic BSD check for memset replacement with a valid HAVE_MEMSET configure check. If nobody has problem with this, I'll apply it and keyword it ~x86-fbsd .
Created attachment 84128 [details, diff] cscope-15.5-memset.patch
thanks for the bug report, committed in -r5