clang does warn about both of those:

    $ cat foo.c

    #include <limits.h>
    int main() {
      int x = INT_MAX+1;
      *(int *)0;
    }

    $ clang foo.c
    foo.c:3:17: warning: overflow in expression; result is -2147483648 with type 'int' [-Winteger-overflow]
            int x = INT_MAX+1;
                           ^
    foo.c:4:2: warning: indirection of non-volatile null pointer will be deleted, not trap [-Wnull-dereference]
            *(int *)0;
            ^~~~~~~~~
    foo.c:4:2: note: consider using __builtin_trap() or qualifying pointer with 'volatile'
    3 warnings generated.