Getting strange output from printf

What causes StringCchPrintfW(buf, buflen, L"%f", double_var) to output "-1.#IO" in Windows Mobile? I am also getting "-1.#IND" sometimes. Documentation mentions "1.#INF" and "-1.#INF" where #IN开发者_Go百科F means infinity, but there is no mention of "#IO" or "#IND".

You're missing the first two parameters to the function. StringCchPrintf formats to a string which you need to provide rather than printing it.