The French do not snack. I remember hosting a birthday party for a bunch of four-year-olds, who refused cake because it wasn't dinner time. The cake had to be parcelled up and sent home with them for dessert.
Nevertheless, most French entrées (which does NOT mean main dishes, but starters) and desserts can be taken as snacks by less discriminately feeding nations. Vol-au-vents, bouchées, and above all patisserie (tarts, small cakes) and viennoiserie (croissants, pains au chocolat, meringues) all go down well with a cup of aternoon tea.
The only thing in French food that qualifies is the Croque Monsieur. It's only a grilled ham and cheese sandwich, but before the arrival of MacDo it was a life saver.