'Disgusted'
"I am disgusted by this recognition," said Senghor, who accompanied his mother and uncle to inconclusive meetings with French authorities looking for information about his father in the 1940s and 1950s.
Two decades later, in 1973, he wrote to Senegal's then-president Leopold Sedar Senghor to ask for support -- a letter left unanswered because it was "too sensitive", his chief of staff later said.
Another decade passed before Senghor in 1982 wrote to French president Francois Mitterrand, who promised to investigate, but that "led to nothing".
Finally, in 2013, historian Mabon came across his father's case in the archives and picked up the fight.
"She got in touch with me and we continued this struggle with France," he said.
The French authorities said that "there is no record" of the murdered soldier, Mabon wrote in her book, "Massacre de Thiaroye: History of a State Lie", published in November.
Following the 1944 massacre, M'Bap Senghor was considered as having disappeared "then as a deserter", before his death was officially confirmed in 1953, Mabon told AFP.
Former French president Francois Hollande ended years of denial over the massacre and vowed in 2014 to return to Senegal a copy of all official documents relating to it -- a promise only "partially kept", historians said.