Asan giving invalid heap-buffer-overflow error

[chiragjain1293]

char *s = calloc(7, 1);
memcpy(s, "1.1.1.1", 7);

char *s2 = strndup(s, 7);

because strndup() is accessing the 8th byte of s, which is obviously an out-of-bounds error. However, ASAN is using its own implementation of this and other functions to detect errors. And in this case the function must not access the nth byte but it does. It is not explicitly stated in strndup() definition but glibc uses strnlen() function to get the size of s, which states that the nth byte will not be accessed. In any case, it is a more-than-reasonable assumption, strndup() does not need to access it so why should it.

[vitalybuka]

Can't reproduce https://godbolt.org/z/KvKEWqr57

[ramosian-glider]

I tried Clang stable revisions 10-19 with the code Vitaly posted and couldn't reproduce the bug either. Should you decide to reopen the bug, please provide a full reproducer along with the Clang version.