user: Demonstrate the C code that generates the assembly output below:

```asm
<main>:
  endbr64
  push   %r12
  push   %rbp
  push   %rbx
  sub    $0x20,%rsp
  mov    %rsi,%rbp
  mov    %fs:0x28,%rax
  mov    %rax,0x18(%rsp)
  xor    %eax,%eax
  cmp    $0x2,%edi
  sete   %dil
  movzbl %dil,%edi
  call   <assert@plt>
  mov    0x8(%rbp),%rdi
  call   <strlen@plt>
  mov    %eax,%ebx
  mov    %eax,%edi
  call   <assert@plt>
  mov    $0x0,%edi
  call   <close@plt>
  mov    $0x1,%edi
  call   <close@plt>
  lea    0x10(%rsp),%rcx
  mov    $0x0,%edx
  mov    D29(%rip),%rax
  mov    (%rax),%esi
  mov    D6(%rip),%rax
  mov    (%rax),%edi
  call   <socketpair@plt>
  test   %rax,%rax
  sete   %dil
  movzbl %dil,%edi
  call   <assert@plt>
  cmpl   $0x0,0x10(%rsp)
  sete   %dil
  movzbl %dil,%edi
  call   <assert@plt>
  cmpl   $0x1,0x14(%rsp)
  sete   %dil
  movzbl %dil,%edi
  call   <assert@plt>
  mov    $0x0,%eax
  call   <fork@plt>
  mov    %rax,%r12
  mov    %rax,%rdi
  not    %rdi
  shr    $0x3f,%rdi
  call   <assert@plt>
  test   %r12,%r12
  je     L14
  mov    $0x1,%edi
  call   <close@plt>
  test   %rax,%rax
  sete   %dil
  movzbl %dil,%edi
  call   <assert@plt>
  mov    0x8(%rbp),%rdi
  mov    %ebx,%esi
  call   <transpose@plt>
  mov    0x8(%rbp),%rsi
  mov    $0x0,%r9d
  mov    $0x0,%r8d
  mov    D33(%rip),%rax
  mov    (%rax),%ecx
  mov    %ebx,%edx
  mov    $0x0,%edi
  call   <sendto@plt>
  cmp    %ebx,%eax
  sete   %dil
  movzbl %dil,%edi
  call   <assert@plt>
  mov    0x8(%rbp),%rsi
  mov    $0x0,%r9d
  mov    $0x0,%r8d
  mov    D58(%rip),%rax
  mov    (%rax),%ecx
  mov    %ebx,%edx
  mov    $0x0,%edi
  call   <recvfrom@plt>
  cmp    %ebx,%eax
  sete   %dil
  movzbl %dil,%edi
  call   <assert@plt>
  mov    $0x0,%edi
  call   <close@plt>
  test   %rax,%rax
  sete   %dil
  movzbl %dil,%edi
  call   <assert@plt>
  lea    0xc(%rsp),%rsi
  mov    $0x0,%edx
  mov    %r12,%rdi
  call   <waitpid@plt>
  cmp    %r12,%rax
  sete   %dil
  movzbl %dil,%edi
  call   <assert@plt>
  cmpl   $0x0,0xc(%rsp)
  sete   %dil
  movzbl %dil,%edi
  call   <assert@plt>
L18:
  mov    0x18(%rsp),%rax
  sub    %fs:0x28,%rax
  jne    L27
  mov    $0x0,%eax
  add    $0x20,%rsp
  pop    %rbx
  pop    %rbp
  pop    %r12
  ret
L14:
  mov    $0x0,%edi
  call   <close@plt>
  test   %rax,%rax
  sete   %dil
  movzbl %dil,%edi
  call   <assert@plt>
  mov    D58(%rip),%r12
  mov    0x8(%rbp),%rsi
  mov    $0x0,%r9d
  mov    $0x0,%r8d
  mov    (%r12),%ecx
  mov    %ebx,%edx
  mov    $0x1,%edi
  call   <recvfrom@plt>
  cmp    %ebx,%eax
  sete   %dil
  movzbl %dil,%edi
  call   <assert@plt>
  mov    0x8(%rbp),%rdi
  mov    %ebx,%esi
  call   <transpose@plt>
  mov    0x8(%rbp),%rsi
  mov    $0x0,%r9d
  mov    $0x0,%r8d
  mov    D33(%rip),%rax
  mov    (%rax),%ecx
  mov    %ebx,%edx
  mov    $0x1,%edi
  call   <sendto@plt>
  cmp    %ebx,%eax
  sete   %dil
  movzbl %dil,%edi
  call   <assert@plt>
  mov    0x8(%rbp),%rsi
  mov    $0x0,%r9d
  mov    $0x0,%r8d
  mov    (%r12),%ecx
  mov    %ebx,%edx
  mov    $0x1,%edi
  call   <recvfrom@plt>
  test   %eax,%eax
  sete   %dil
  movzbl %dil,%edi
  call   <assert@plt>
  mov    $0x1,%edi
  call   <close@plt>
  test   %rax,%rax
  sete   %dil
  movzbl %dil,%edi
  call   <assert@plt>
  jmp    L18
L27:
  call   <__stack_chk_fail@plt>
```

assistant: ```c
int main(int ac, char **av) {
  assert(ac == 2);
  const int len = strlen(av[1]);
  assert(len);
  (void)close(0);
  (void)close(1);
  int sv[2];
  assert(socketpair(AF_UNIX, SOCK_STREAM, 0, sv) == 0);
  assert(sv[0] == 0);
  assert(sv[1] == 1);
  pid_t pid = fork();
  assert(pid >= 0);
  if (pid) {
    assert(close(1) == 0);
    transpose(av[1], len);
    assert(sendto(0, av[1], len, MSG_DONTROUTE, NULL, 0) == len);
    assert(recvfrom(0, av[1], len, MSG_WAITALL, NULL, NULL) == len);
    assert(close(0) == 0);
    int status;
    assert(waitpid(pid, &status, 0) == pid);
    assert(status == 0);
  } else {
    assert(close(0) == 0);
    assert(recvfrom(1, av[1], len, MSG_WAITALL, NULL, NULL) == len);
    transpose(av[1], len);
    assert(sendto(1, av[1], len, MSG_DONTROUTE, NULL, 0) == len);
    assert(recvfrom(1, av[1], len, MSG_WAITALL, NULL, NULL) == 0);
    assert(close(1) == 0);
  }
  return 0;
}
```