How to enable warnings for implicit casts to a narrower type?

[Pete]

I'd like to have warnings for code like this:

void blah(char c) {}

int main() {
  int a = 500;
  blah(a); // want a warning here
  char b = a; // warning here would be nice too
}


Can this be achieved? -Wall and -Wconversion don't do it.
Thanks...