Does "glad" have a comparative form?

[Chicken Sandwich]

According to the Longman Dictionary of Contemporary English, "glad" does not have a comparative form, see glad - Definition from Longman English Dictionary Online. However, other sources indicate that there is one, see Gladder - definition of Gladder by the Free Online Dictionary, Thesaurus and Encyclopedia.

Has Longman made a mistake saying that there is no comparative form?

Thank you.

[emsr2d2]

"Gladder" is fine with me and with several online dictionaries. Having said that, I'm not sure I've ever said it. I just tried to put it in a sentence in my head and it sounded rather odd. I would probably use:

I am more glad than you could possibly imagine.