On Mon, 25 Oct 2004 14:17:11 +0100, Ben Hutchings <ben.hutchings@businesswebsoftware.com> wrote:
Caleb Epstein wrote:
On Sat, 23 Oct 2004 07:10:48 +0000 (UTC), Darryl Green <darryl.green@unitab.com.au> 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@gmail.com