I just tried the following simple example:

  #include <string.h>

  struct S {
    int i;
    char c;
    int j;
  };

  void f(void) {
    struct S s1 = { 0, 0, 0 }, s2 = { 0, 0, 0 };
    memcpy(&s1, &s2, 9);
  }

  int main(void) {
    f();
    return 0;
  }

MSVC, Clang, and PC-Lint are all silent on the code (which is reasonable behavior since it's impossible to glean programmer intent from that snippet -- maybe the programmer really only wants the first nine bytes!). (Btw, yes, I am using the analyzer features for MSVC and Clang, not just relying on high warning levels.)