read_from_old_location is set twice in router_reload_router_list_impl
The second mutation appears to exist so that the conditional above it can exist. Is there a reason to check the return value?
read_from_old_location = 1; log_notice(LD_DIR, "Couldn't read %s; trying to load routers from old " "location %s.", fname, altname); if ((store->mmap = tor_mmap_file(altname))) read_from_old_location = 1;