Re: Patch to add snprintf/vsnprintf to libiberty

[Paolo Carlini <pcarlini at unitus dot it>]

Kaveh R. Ghazi wrote:

> B.  What do we return when n < real length?  n? real_length?
> (`real_length' is the length the output would have been had we given a
> large enough 'n'.)
> The standard above says the number of characters transmitted ('n'),
> but I *think* c99 says the number that *would* have been transmitted,
> i.e. real_length.  Irix6.5 returns n while solaris2.8 returns
> real_length.
> I chose the real_length.
Definitely, this behavior - i.e., that conforming to the C99 standard - 
is the one which would be most useful for libstdc++-v3. For instance, 
consider this example from num_put::_M_convert_int (__convert_from_v 
calls snprintf and little more, not relevant for the present discussion):

...

#ifdef _GLIBCPP_USE_C99
   // First try a buffer perhaps big enough.
   int __cs_size = 64;
   char* __cs = static_cast<char*>(__builtin_alloca(__cs_size));
   int __len = __convert_from_v(__cs, __cs_size, __fbuf, __v,
                    _S_c_locale);
   // If the buffer was not large enough, try again with the correct size.
   if (__len >= __cs_size)
     {
       __cs_size = __len + 1;
       __cs = static_cast<char*>(__builtin_alloca(__cs_size));
       __len = __convert_from_v(__cs, __cs_size, __fbuf, __v,
                    _S_c_locale);
     }

...

Paolo.