I just ran the static analysis tool "cppcheck" over
the source code of flac-1.3.0
It said many things, including
[utf8/charset.c:59] -> [utf8/charset.c:59]: (style) Same expression on both sides of '||'.
Source code is
if (!*s1 || !*s1)
if (!*s1 || !*s2)
might be better code. I also checked your current development
source code and the bug exists there too.