C library functions are always like: "SYNOPSIS. This function converts foos into bars depending on the user locale. ARGUMENTS. src and dest pointers must be distinct; it is undefined behavior if they are not QPU-aligned. RETURN VALUE. Returns the number of foos converted. A zero value indicates failure, or that zero foos were converted. A negative value indicates that the final foo was only partially converted (function got tired). Check this global variable to find out why."