Invalid check when moving line

[oerdnj]

Hey,

I believe the check here: https://github.com/conformal/backtrace/blob/master/libbacktrace/backtrace.c#L264

should in fact be:

if (csz >= sz - (current - (char *)rv)) {
...
}

Currently, as written, the condition can't ever be true because strlcpy() unless line[x] was not properly NULL terminated (e.g. runaway string), but you probably wanted to check if strlcpy() was able to fit the whole line[i] inside the cur buffer.