On Tue Oct 10 12:31:51 2017, ckb wrote:
> Failed test cases:
>    lib/isc/tests/buffer_test:isc_buffer_printf
> 
> isc_buffer_printf: [0.004462s] Failed: 1 checks failed; see output for
> more details
> 
> output:
> tc-se:*** Check failed: buffer_test.c:279: result != ISC_R_FAILURE
> 
> Fails on freebsd and OSX

A "%" format specifier hits this part of the specification.

"If a conversion specification does not match one of the above forms, the behavior is undefined. If any argument is not the correct type for the corresponding conversion specification, the behavior is undefined."

http://pubs.opengroup.org/onlinepubs/9699919799/functions/fprintf.html

As you can see on Darwin you get n=0 and nothing written to the buffer.

[rock:~/git/bind9] marka% cat oo.c
#include <stdio.h>
#include <string.h>
int
main(int argc, char **argv) {
	char buf[15];
	int n;

	memset(buf, 0, sizeof(buf));
	n = snprintf(buf, sizeof(buf), "%");
	printf("%02x %02x %d\n", buf[0], buf[1], n);
}

[rock:~/git/bind9] marka% cc oo.c -Wno-format
[rock:~/git/bind9] marka% ./a.out
00 00 0
[rock:~/git/bind9] marka% 

I recommend that we remove this test case as it depends on unspecified behaviour.