Re: [PATCH 1/2] string: Add stracpy and stracpy_pad mechanisms

[Joe Perches <joe@perches.com>]

(adding Chris Metcalf)

On Tue, 2019-07-23 at 15:41 +0000, David Laight wrote:
> From: Rasmus Villemoes
> > Sent: 23 July 2019 07:56
> ...
> > > +/**
> > > + * stracpy - Copy a C-string into an array of char
> > > + * @to: Where to copy the string, must be an array of char and not a pointer
> > > + * @from: String to copy, may be a pointer or const char array
> > > + *
> > > + * Helper for strscpy.
> > > + * Copies a maximum of sizeof(@to) bytes of @from with %NUL termination.
> > > + *
> > > + * Returns:
> > > + * * The number of characters copied (not including the trailing %NUL)
> > > + * * -E2BIG if @to is a zero size array.
> > 
> > Well, yes, but more importantly and generally: -E2BIG if the copy
> > including %NUL didn't fit. [The zero size array thing could be made into
> > a build bug for these stra* variants if one thinks that might actually
> > occur in real code.]
> 
> Probably better is to return the size of the destination if the copy didn't fit
> (zero if the buffer is zero length).
> This allows code to do repeated:
> 	offset += str*cpy(buf + offset, src, sizeof buf - offset);


> and do a final check for overflow after all the copies.
> 
> The same is true for a snprintf()like function

Chris?  You added this function.
Do you have an opinion here?