Re: [boost] Re: [Q]: What is the recommended logging facility forboost: log4cpp or ??

From: Caleb Epstein (caleb.epstein_at_[hidden])
Date: 2004-10-25 08:57:17

On Mon, 25 Oct 2004 14:17:11 +0100, Ben Hutchings
<ben.hutchings_at_[hidden]> wrote:
> Caleb Epstein wrote:
> > On Sat, 23 Oct 2004 07:10:48 +0000 (UTC), Darryl Green
> > <darryl.green_at_[hidden]> wrote:
> >
> >
> >>      char buf[101];
> >>      va_list args;
> >>      va_start(args, fmt);
> >>      int n = vsnprintf (buf, 101, fmt, args));
> >>      va_end(args);
> >>      if (n < 0) return;
> >
> >
> > This is one of the reasons I find the *snprintf functions to be pure
> > evil.  They don't return -1 when the output would be too long, they
> > return the size they WOULD have written if the buffer was large
> > enough.
> 
> That's not evil; it's extremely useful if you want to dynamically
> allocate a large enough buffer.  All you have to do is check that the
> return value is less than or equal to the length you passed in.
> 
> (Aside: what if the length is greater than INT_MAX?)
> 
> > Is this code doing what you intend?
> 
> When built with Visual C++, it probably is.  MS documents this function
> as returning a negative value in case of error.  A portable test would
> be size_t(n) > sizeof(buf).

OK, perhaps it isn't *pure* evil, but I have seen lots of code that
assumes *snprintf returns -1 when the buffer is too small.  It
doesn't, or at least not portably.

I just think this behavior is confusing w/r/t the behavior of other
standard library functions and leads to subtle program bugs, which is
why I dislike this family of functions.

-- 
Caleb Epstein
caleb.epstein_at_[hidden]