Finding the scope of setting some variable?

I'm interested in finding a tool that, given some declared variable foobar, shows me the start of the scopes of where foobar is set, incremented, etc. Like:

File with declaration:

int foobar;

File with scope:

//...
void func(int &foobar) {
    foobar = 42;
}

File with other scope:

//...
if (this_and_that == true) {
    foobar++;
}

…and so on. A compiler clearly does/uses this, but that feels like a dark road to go down. Is there a standalone tool that I may use? Thank you!