The address start must be a multiple of the page size. All pages containing a part of the indicated range are unmapped, and subsequent references to these pages will generate SIGSEGV. It is not an error if the indicated range does not contain any mapped pages. Therefore this is not the bug. The issues almost certainly lies elsewhere. It's generally a bad idea to strace wine. The results are not meaningful once control is passed to the Windows application. Instead, use the builtin debugging infrastructure to narrow down the problem, a +tid,+relay,+seh trace might prove informative. thanks -mike