代码

struct DuckInfo {
    unsigned long abi_version; const char *stdin_ptr; unsigned long stdin_size;
    char *stdout_ptr; unsigned long stdout_limit; unsigned long stdout_size;
    char *stderr_ptr; unsigned long stderr_limit; unsigned long stderr_size;
    const char *IB_ptr; unsigned long IB_limit; char *OB_ptr; unsigned long OB_limit;
    unsigned long tsc_frequency;
} __attribute__((packed));
#define AT_DUCK 0x6b637564
int plus(int a, int b) { return a + b; }
void __libc_start_main(int (*m)(int,char**,char**), int argc, char **argv, void *x, void *y, void *z) {
    unsigned long *q = (unsigned long*)&argv[argc + 1];
    while (*q) q++; q++;
    struct DuckInfo *d = 0;
    while (q[0]) { if (q[0] == AT_DUCK) { d = (struct DuckInfo*)q[1]; break; } q += 2; }
    d->stdout_ptr[0] = 'x';
    d->stdout_size = 1;
    __asm__ volatile("mov $60, %%rax; xor %%rdi, %%rdi; syscall" ::: "rax","rdi","memory");
    __builtin_unreachable();
}

评测结果