// Clean negative control: no vulnerability.
#include <string.h>
#include <unistd.h>
__attribute__((noinline)) void ok(const char* src) {
    char buf[64];
    strncpy(buf, src, sizeof(buf) - 1); // bounded, safe
    buf[63] = '\0';
    write(1, buf, sizeof(buf));
}
int main(int argc, char** argv) {
    if (argc > 1)
        ok(argv[1]);
    return 0;
}