GCC - Unused Variable Warning inside Structs

I am searching for a solution where GCC (Arm-Embedded Version) is able to tell me if a variable is not existing at all, when allocated as part of a struct.

The current examples do not warn at all, which i would like to change.

Example 1:

Example 1 has 3 variables from a sturct: var1: assigned but never referenced elsewhere, therefore i want to remove it var2: not even assigned, makes no sense to waste ram here, remove it return: assigned and referenced, everything ok.

therefore i would like to get 2 warnings here.

struct mydummy_t
{
    bool var1;
    bool var2;
    int return;
};

static mydummy_t dummy;

int main()
{
    dummy.var1 = true;
    dummy.return = 15;
    return dummy.return;
}

Example 2:

same as example one but now we have a class constructor which initially addresses every variable, but again, not all of them are referenced.

struct mydummy_t
{
    mydummy_t() : var1(false), var2(true), return(-1) {}
    bool var1;
    bool var2;
    int return;
};

static mydummy_t dummy;

int main()
{
    dummy.var1 = true;
    dummy.return = 15;
    return dummy.return;
}