voici ce que dit la documentation sur cette option:
-Wreorder (C++ only)
Warn when the order of member initializers given in the code does not
match the order in which they must be executed. For instance:
struct A {
int i;
int j;
A(): j (0), i (1) { }
};
The compiler will rearrange the member initializers for i and j to
match the declaration order of the members, emit-ting a warning to that
effect. This warning is enabled by -Wall.ça correspond à votre code qui a une inversion dans l'ordre d'initialisation des attributs par rapport à l'ordre de leur déclaration.