clang

temp.c:5:13: warning: length modifier 'I64' results in undefined behavior or no effect with 'd' conversion specifier [-Wformat]
    scanf("%I64d", &a);
           ~^~~~
temp.c:5:20: warning: format specifies type '__int64 *' (aka 'long long *') but the argument has type 'int *' [-Wformat]
    scanf("%I64d", &a);
           ~~~~~   ^~
           %d

source.c

#include <stdio.h>

int main() {
    int a;
    scanf("%I64d", &a);
}