Hi Mikołaj, your commit seems to have an uninitialized variable; see http://kegel.com/wine/valgrind/logs-2008-06-20/vg-comdlg32_filedlg-diff.txt
One of the errors:
Conditional jump or move depends on uninitialised value(s) at strlenW (unicode.h:212) by lstrlenW (string.c:384) by GetFileDialog95W (filedlg.c:484) by GetOpenFileNameW (filedlg.c:3891) by test_DialogCancel (filedlg.c:90) by func_filedlg (filedlg.c:128) by run_test (test.h:449) by main (test.h:498) Uninitialised value was created by a stack allocation at test_DialogCancel (filedlg.c:56)