Consider non-ASCII characters in domains.

[spladug]

No description provided.

[jamt9000]

To summarise the issues:

For inline links, a non-ASCII character immediately after the protocol (or pseudo-protocol eg. '#', '/') will cause the link to fail due to isalnum checking in sd_autolink_issafe, called from rndr_link. So [](http://www.☃.net/) works, [](http://☃.net/) fails.

For autolinks, the above bug still occurs (because sd_autolink_issafe is called from sd_autolink__url) , but additionally any non-ASCII character appearing 1) anywhere before the first period in the domain or 2) immediately after a period will cause the link to fail due to overzealous check_domain, which will miscount the number of periods in the domain due to breaking from the loop at the first non-alnum-or-dash character encountered (check_domain assumes the domain has a period in, which is isn't always the case, eg http://io). Use of isalnum(data[0]) would also cause a problem, but it is masked by the previous bug.

So:
http://☃.net fails (sd_autolink_issafe)
http://a☃b.net fails (np = 0 since break before period)
http://www.a☃b.net works
http://www.☃b.net fails (isalnum(data[i - 1]) = 0 since data[i-1] is period)
http://www.a☃.net works
http://www.a☃ works