This is usually where I start citing B. S. Johnson's dictum about no writing being new, that all literature essentially comes from autobiographical sources: even the three-headed monster of science fiction derives from the concepts three, head, and monster. D. H. Lawrence's Sons and Lovers (1913) is an example of autofiction par excellence, and I forget who said that D. H. Lawrence incorporated his whole life experiences into his books, that he was incapable of 'inventing' any purely original characters, but of course he wasn't French and he died over eighty-five years ago.
Jules Renard was French, and his novel Poil de Carotte (1894) is a prime example of the (sub)-genre. Enter Hervé Bazin, the first part of his autobiographical trilogy being Vipère au poing (1948), yet another example of autofiction avant la lettre. Here the story begins in 1922 and continues until several years later.
Jean Rezeau (nicknamed Brasse-Bouillon), eight years of age, lives with his slightly older brother Frédie (or Chiffe) and his paternal grandmother until her death. Then everything changes, and the parents have to return. The father Jacques Rezeau, doctor in Law who has taught in a university in China, married Paule Pluvignec from a wealthy family: he is a timid man more interested in the scholarly study of insects, whereas Paule (almost always referred as Folcoche, a mixture of the feminine 'mad' ('folle') and 'female pig' ('cochonne'), is an aggressive, and surely half-mad, woman whose passion (when not beating her children) is, er, collecting stamps.
The parents return after the grandmother's death, along with the youngest son Marcel, who becomes a kind of double agent in the civil war which develops between the brothers and Folcoche. And Folcoche's agents dwindle as she frightens off the domestics, the (religious) teachers, and so on. Largely, though, this develops into a war between the narrator Brasse-Bouillon and Folcoche, in the end with the sexually mature son forcing his mother (if that word can be uttered without vomiting) to accept if not defeat then a kind of stalemate by a mixture of maturity and cunning. Very amusing in a rather chilling kind of way, and of course a classic of French literature.