Asan complains about zero length string in sprintf

[ankurrj7]

Asan complain buffer overflow in this example

#include <stdio.h>
#include<string.h>
#include<stdlib.h>

int main()
{
   char buffer[10];
   char *s = (char*)malloc(8);
   memcpy(s,"abcdefgh",8);
   int j = snprintf(buffer, 4, "%.0s\n", s);
   return 0;
}

==3850459==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x602000000018 at pc 0x7f325e905786 bp 0x7ffd41264150 sp 0x7ffd412638c8
READ of size 9 at 0x602000000018 thread T0
#0 0x7f325e905785 (/lib64/libasan.so.5+0x55785)
#1 0x7f325e907555 in vsnprintf (/lib64/libasan.so.5+0x57555)
#2 0x7f325e90782e in __interceptor_snprintf (/lib64/libasan.so.5+0x5782e)
#3 0x4009ab in main /tmp/sample.c:11
#4 0x7f325e50e492 in __libc_start_main (/lib64/libc.so.6+0x23492)
#5 0x40082d in _start (/tmp/a.out+0x40082d)

0x602000000018 is located 0 bytes to the right of 8-byte region [0x602000000010,0x602000000018)
allocated by thread T0 here:
#0 0x7f325e99fb98 in __interceptor_malloc (/lib64/libasan.so.5+0xefb98)
#1 0x400969 in main /tmp/sample.c:9
#2 0x7f325e50e492 in __libc_start_main (/lib64/libc.so.6+0x23492)

it seems ASAN does not recognises "%.0s" format specifier ?
and it seems to continue reading bytes (and overshoot since there is no null terminator ?)

if i change " int j = snprintf(buffer, 4, "%.0s\n", s);" to int j = snprintf(buffer, 4, "%.1s\n", s);
it works fine