RE: [PATCH v2] checkpatch: add check for snprintf to scnprintf

[David Laight <David.Laight@ACULAB.COM>]

From: Justin Stitt
> Sent: 21 February 2024 22:12
> 
> I am going to quote Lee Jones who has been doing some snprintf ->
> scnprintf refactorings:
> 
> "There is a general misunderstanding amongst engineers that
> {v}snprintf() returns the length of the data *actually* encoded into the
> destination array.  However, as per the C99 standard {v}snprintf()
> really returns the length of the data that *would have been* written if
> there were enough space for it.  This misunderstanding has led to
> buffer-overruns in the past.  It's generally considered safer to use the
> {v}scnprintf() variants in their place (or even sprintf() in simple
> cases).  So let's do that."

While generally true, there are places that really do want to
detect (and error) overflow.
That isn't possible with scnprintf().

I'm not sure what the solution is though.
Having a function that returns a negative value on overflow is also
likely to get misused.
seq_printf() (or whatever it is called) may let you check,
but it is hardly a cheap wrapper and a bit of a PITA to use.

	David

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