When m-chlorobenzaldehyde is treated with 50%KOH solution, the product(s) obtained are potassium metachloro benzoate and metachloro benzyl alcohol. It undergoes Cannizzaro reaction in which one molecule is oxidized to metachloro benzoic acid and other molecule is reduced to metachloro benzyl alcohol. 
Related Theory The Cannizzaro reaction is not given by Acetaldehyde. Aldehydes that contains alpha hydrogen atoms are not involved in Cannizzaro reaction and aldehyde like acetaldehyde contains alpha hydrogen in it. Caution m-chlorobenzaldehyde has no α-hydrogen and hence gives Cannizzaro's reaction.