testlist <- list(id = c(-621726556L, -1331494887L, 1854878590L, 314985932L,  1361933119L, -1262797933L, -1571830262L, -555281357L, 1176038391L,  -1125445590L, 2051319948L, -555281357L, 600611799L, -2015925719L,  640758675L, -2045256755L, 818332908L, -1294723540L, 415152419L,  -1290633258L, -568676763L, -250049000L, 1237429200L, -645489399L,  1298265599L, 889924430L, -907775620L, -152022060L), time = c(352546080L,  77995038L, 1848672759L, -273393355L, -2067478347L, 609885071L,  416334778L, -176991733L, 2009017211L, 1715968468L, 1998244710L,  -836461486L, -396097780L, -1088185385L))
result <- do.call(fixest:::cpp_find_duplicates,testlist)
str(result)