Do the format strings for printf et al behave differently on Borland C and in GCC?

Question

I am working on porting an old codebase from Borland C to C99. I have come across the following function, which looks like it should copy zero bytes into a buffer.

sprintf(tx_tcp_buf,"%0s%0s%0s%0s%0s%0s",strHeader, ccSTX, drValidity, ccUS, "Y",ccETX);

The declaration of tx_tcp_buf is static BYTE tx_tcp_buf[150] = {0};.

All of strHeader, ccSTX, drValidity, ccUS, and ccETX are of type char *.

What's bugging me is the length specifier in the format string. It is my first time of encountering a length specifier of zero, for a string. Here, we've got %0s which from what I read should copy zero bytes. (So what is the above call to sprintf even doing?)

I don't have a copy of Borland C, but I've tried the following program in GCC:

#include <stdio.h>
int main() {
     char buf[256];
     char * hello = "Hello, World!\n";
     printf(buf, "%0s", hello);
     printf("\"%s\"\n",buf);
}

It's output is

"Hello, World!
"

Evidently the %0s isn't doing much that %s wouldn't do. But with -pedantic -Wall -std=c99, I get a warning, which specifically mentions some gnu_printf format:

warning: '0' flag used with '%s' gnu_printf format [-Wformat=]
       sprintf(tx_tcp_buf,"%0s%0s%0s%0s%0s%0s",strHeader,ccSTX,drStatus,ccUS,"I",ccETX);

Do different compilers have different behaviours here? I'm especially interested in Borland C, and GCC. But it would be good to know about others.