GetFolderPathW needs wchar_t and can otherwise fail (returning an invalid path) and use AppData path instead of users home directory. Use Local AppData instead of roaming to users on domain networks aren't uploading DAG files to servers.

libethash/io_win32.c

@@ -87,9 +87,9 @@ bool ethash_file_size(FILE* f, size_t* ret_size)
 
 bool ethash_get_default_dirname(char* strbuf, size_t buffsize)
 {
-	static const char dir_suffix[] = "Appdata\\Ethash\\";
+	static const char dir_suffix[] = "Ethash\\";
 	strbuf[0] = '\0';
-	if (!SUCCEEDED(SHGetFolderPathW(NULL, CSIDL_PROFILE, NULL, 0, (WCHAR*)strbuf))) {
+	if (!SUCCEEDED(SHGetFolderPathA(NULL, CSIDL_LOCAL_APPDATA, NULL, 0, (CHAR*)strbuf))) {
 		return false;
 	}
 	if (!ethash_strncat(strbuf, buffsize, "\\", 1)) {