MADRID — Ben Affleck’s “Argo” will have its European premiere out of competition at September’s San Sebastian Film Festival, adding Hollywood studio weight to the fest line-up.The 1979 Tehran hostage thriller is produced by Warner Bros. Pictures in association with Graham King’s GK Films and George Clooney and Grant Heslov’s Smoke House Pictures. Based on true events, Affleck directs and stars in “Argo” as a CIA specialist who concocts a life-or-death gambit to help six U.S. diplomats, holed up at the Canadian ambassador’s house during the U.S. hostage crisis, escape from Iran. Affleck and co-stars Alan Arkin and John Goodman will present “Argo” at San Sebastian, which runs Sept. 21 to 29. Pic world preems at the Toronto Film Festival a few weeks earlier. “Argo” is Affleck’s third movie as a director after “Gone, Baby, Gone” and “The Town.” While Spain’s box office has been punished by the European financial crisis, with blockbusters and local youth fare underperforming, “Argo” is the kind of upscale, adult-skewed movie that has occasionally broken out this year to standout box office. Directed by Alexander Payne, Clooney-starrer “The Descendants” grossed $11 million, placing fourth in B.O. charts for the first half of the year.