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

From: Ben Hutchings (ben.hutchings_at_[hidden])
Date: 2004-10-25 08:17:11

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).

Ben.