• coder <coder_member pathlink.com> May 10 2004
• coder <coder_member pathlink.com> May 10 2004
• "Jackson" <fangzhengzhu kingsoft.com> Aug 30 2004

Does dmc implement the c99 function snprintf? My code containing calls to
snprintf won't link. However vsnprintf seems to be implemented which makes
snprintf easy to write. Is this an oversight.

In article <c7ohe4$fma$1 digitaldaemon.com>, coder says...
Does dmc implement the c99 function snprintf? My code containing calls to
snprintf won't link. However vsnprintf seems to be implemented which makes
snprintf easy to write. Is this an oversight.


Also, I don't think vsnprintf is correct according to the standard.
The program below always prints -1 when it should print 13.

#include <stdio.h>
#include <stdarg.h>

int snprintf(char *str, int n, char *fmt, ...)
{
va_list a;

va_start(a, fmt);

int ret = vsnprintf(str, n, fmt, a);

va_end(a);

return ret;
}

int main()
{
char str[10];

int n = snprintf(str, 10, "Hello, World\n");

printf("%d\n",n);

return 0;
}

The standard says:
"
The vsnprintf [also snprintf] function returns the number of characters that
would have been written had n been sufficiently large, not counting the
terminating null character, or a negative value if an encoding error occurred.
Thus, the null-terminated output has been completely written if and only if the
returned value is nonnegative and less than n.
"

Therefore the call to snprintf should return strlen("Hello World\n") so I'd know
to allocate an array of at least strlen("Hello World\n")+1 bytes of memory. That
allows code like this to work.

int n = snprintf((char*)0, 0, fmt, a1, a2, aetc);
char *str=malloc(n+1);
snprintf(str, n+1, fmt, a1, a2, aetc);

It solves the problem of not knowing how large sprintf's buffer should be.

If the number of charactors to written exceed count,then -1 will be
returned.

So just increase count.

"coder" <coder_member pathlink.com> дÈëÏûÏ¢ÐÂÎÅ
:c7ohe4$fma$1 digitaldaemon.com...
 Does dmc implement the c99 function snprintf? My code containing calls to
 snprintf won't link. However vsnprintf seems to be implemented which makes
 snprintf easy to write. Is this an oversight.