user: 请将这段汇编代码片段转换成等效的C代码：

```asm
<main>:
  endbr64
  push   %rbp
  mov    %rsp,%rbp
  sub    $0x20,%rsp
  mov    $0x10,%edi
  call   <malloc@plt>
  mov    %rax,-0x10(%rbp)
  mov    -0x10(%rbp),%rax
  movq   $0x0,(%rax)
  mov    -0x10(%rbp),%rax
  movq   $0x0,0x8(%rax)
  jmp    L129
L35:
  mov    -0x10(%rbp),%rax
  mov    %rax,-0x20(%rbp)
  jmp    L73
L55:
  mov    $0x0,%eax
  call   <__VERIFIER_nondet_int@plt>
  test   %eax,%eax
  je     L42
  mov    -0x20(%rbp),%rax
  mov    (%rax),%rax
  mov    %rax,-0x20(%rbp)
  jmp    L73
L42:
  mov    -0x20(%rbp),%rax
  mov    0x8(%rax),%rax
  mov    %rax,-0x20(%rbp)
L73:
  mov    -0x20(%rbp),%rax
  mov    (%rax),%rax
  test   %rax,%rax
  je     L123
  mov    -0x20(%rbp),%rax
  mov    0x8(%rax),%rax
  test   %rax,%rax
  jne    L55
L123:
  mov    -0x20(%rbp),%rax
  mov    (%rax),%rax
  test   %rax,%rax
  jne    L128
  mov    $0x0,%eax
  call   <__VERIFIER_nondet_int@plt>
  test   %eax,%eax
  je     L128
  mov    $0x10,%edi
  call   <malloc@plt>
  mov    %rax,%rdx
  mov    -0x20(%rbp),%rax
  mov    %rdx,(%rax)
  mov    -0x20(%rbp),%rax
  mov    (%rax),%rax
  movq   $0x0,(%rax)
  mov    -0x20(%rbp),%rax
  mov    (%rax),%rax
  movq   $0x0,0x8(%rax)
L128:
  mov    -0x20(%rbp),%rax
  mov    0x8(%rax),%rax
  test   %rax,%rax
  jne    L129
  mov    $0x0,%eax
  call   <__VERIFIER_nondet_int@plt>
  test   %eax,%eax
  je     L129
  mov    $0x10,%edi
  call   <malloc@plt>
  mov    %rax,%rdx
  mov    -0x20(%rbp),%rax
  mov    %rdx,0x8(%rax)
  mov    -0x20(%rbp),%rax
  mov    0x8(%rax),%rax
  movq   $0x0,(%rax)
  mov    -0x20(%rbp),%rax
  mov    0x8(%rax),%rax
  movq   $0x0,0x8(%rax)
L129:
  mov    $0x0,%eax
  call   <__VERIFIER_nondet_int@plt>
  test   %eax,%eax
  jne    L35
  movq   $0x0,-0x20(%rbp)
  mov    $0x10,%edi
  call   <malloc@plt>
  mov    %rax,-0x18(%rbp)
  mov    -0x18(%rbp),%rax
  movq   $0x0,(%rax)
  mov    -0x18(%rbp),%rax
  mov    -0x10(%rbp),%rdx
  mov    %rdx,0x8(%rax)
  jmp    L20
L37:
  mov    -0x18(%rbp),%rax
  mov    %rax,-0x8(%rbp)
  mov    -0x18(%rbp),%rax
  mov    (%rax),%rax
  mov    %rax,-0x18(%rbp)
  mov    -0x8(%rbp),%rax
  mov    0x8(%rax),%rax
  mov    %rax,-0x20(%rbp)
  mov    -0x8(%rbp),%rax
  mov    %rax,%rdi
  call   <free@plt>
  mov    -0x20(%rbp),%rax
  mov    (%rax),%rax
  test   %rax,%rax
  je     L74
  mov    $0x10,%edi
  call   <malloc@plt>
  mov    %rax,-0x8(%rbp)
  mov    -0x8(%rbp),%rax
  mov    -0x18(%rbp),%rdx
  mov    %rdx,(%rax)
  mov    -0x20(%rbp),%rax
  mov    (%rax),%rdx
  mov    -0x8(%rbp),%rax
  mov    %rdx,0x8(%rax)
  mov    -0x8(%rbp),%rax
  mov    %rax,-0x18(%rbp)
L74:
  mov    -0x20(%rbp),%rax
  mov    0x8(%rax),%rax
  test   %rax,%rax
  je     L140
  mov    $0x10,%edi
  call   <malloc@plt>
  mov    %rax,-0x8(%rbp)
  mov    -0x8(%rbp),%rax
  mov    -0x18(%rbp),%rdx
  mov    %rdx,(%rax)
  mov    -0x20(%rbp),%rax
  mov    0x8(%rax),%rdx
  mov    -0x8(%rbp),%rax
  mov    %rdx,0x8(%rax)
  mov    -0x8(%rbp),%rax
  mov    %rax,-0x18(%rbp)
L140:
  mov    -0x20(%rbp),%rax
  mov    %rax,%rdi
  call   <free@plt>
L20:
  cmpq   $0x0,-0x18(%rbp)
  jne    L37
  mov    $0x0,%eax
  leave
  ret
```

assistant: ```c
int main() {
  struct TreeNode {
    struct TreeNode *left;
    struct TreeNode *right;
  };
  struct StackItem {
    struct StackItem *next;
    struct TreeNode *node;
  };
  struct TreeNode *root = malloc(sizeof(*root)), *n;
  root->left = ((void *)0);
  root->right = ((void *)0);
  while (__VERIFIER_nondet_int()) {
    n = root;
    while (n->left && n->right) {
      if (__VERIFIER_nondet_int())
        n = n->left;
      else
        n = n->right;
    }
    if (!n->left && __VERIFIER_nondet_int()) {
      n->left = malloc(sizeof(*n));
      n->left->left = ((void *)0);
      n->left->right = ((void *)0);
    }
    if (!n->right && __VERIFIER_nondet_int()) {
      n->right = malloc(sizeof(*n));
      n->right->left = ((void *)0);
      n->right->right = ((void *)0);
    }
  }
  n = ((void *)0);
  struct StackItem *s = malloc(sizeof(*s)), *st;
  s->next = ((void *)0);
  s->node = root;
  while (s != ((void *)0)) {
    st = s;
    s = s->next;
    n = st->node;
    free(st);
    if (n->left) {
      st = malloc(sizeof(*st));
      st->next = s;
      st->node = n->left;
      s = st;
    }
    if (n->right) {
      st = malloc(sizeof(*st));
      st->next = s;
      st->node = n->right;
      s = st;
    }
    free(n);
  }
  return 0;
}
```