[ECOS] vsnprintf

[Jonathan Larmour]

Bob Koninckx wrote:
> Seems like vsnprintf _always_ returns the number of bytes actually
> written, also if the provided buffer was too small, in which case the
> number of bytes that would have been written if a large enough buffer
> would have been available should be returned.
> 
> Anyone else seen this ? Did I miss something ?

I believe the behaviour you want is new in C99 (certainly new as far as 
the eCos C library is concerned :-)). Or rather, C99 added the *nprintf 
functions (vsnprintf and snprintf). This was to reflect existing practice, 
like we have in eCos, except that they defined the return value 
differently from that existing practice.

For example, the glibc manpage for vsnprintf says:
-=-=-=-=-
These functions return the number of characters printed (not including the 
trailing `\0' used to end output to strings). snprintf and vsnprintf do 
not write more than size bytes (including the trailing '\0'), and return 
-1 if the output was truncated due to this limit.  (Thus until glibc 
2.0.6. Since glibc 2.1 these functions follow the  C99 standard and return 
the number of characters (excluding the trailing '\0') which would have 
been written to the final string if enough space had  been  available.)
-=-=-=-=-

It's their choice since those functions weren't defined officially earlier.

For now, we've ignored the issue :-). We're not C99 compliant in so many 
other ways anyway.

Jifl
-- 
eCosCentric       http://www.eCosCentric.com/       <info@eCosCentric.com>
--[ "You can complain because roses have thorns, or you ]--
--[  can rejoice because thorns have roses." -Lincoln   ]-- Opinions==mine


-- 
Before posting, please read the FAQ: http://sources.redhat.com/fom/ecos
and search the list archive: http://sources.redhat.com/ml/ecos-discuss