On Fri, Oct 30, 2009 at 12:12:40PM -0700, Shawn O. Pearce wrote:
> > If you really just want to initialize to zero, using
> >
> > char linelen[5] = { 0 };
>
> Bleh, I find that has hard to grok as what we have now. Perhaps my
> understanding of the relevant standards is incomplete, but I'd read
> that as linelen[0] = 0, but the other 4 positions are undefined
> and may be not be initialized.
C isn't that into undefined things. In this particular case, all
remaining values will be initialized to zero.
> I actually considered this one, but again I wasn't clear what would
> happen in the standard C library when we fed a string that wasn't
> actually NUL terminated. Is the library permitted to call strlen()
> before formatting? If so strlen() could SIGSEGV if we are unlucky
> and no NUL is present between our string and the end of the assigned
> memory region.
The linux manpage says "If a precision is given, no null byte
need be present". This text is copied verbatim out of the Posix
specification, so a C library that failed to handle this would be
non-compliant.
I think the %.4s is clearest, and is, in fact, somewhat
idiomatic.
David
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