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

```asm
<string_join>:
  endbr64
  push   %rbp
  mov    %rsp,%rbp
  push   %r15
  push   %r14
  push   %r13
  push   %r12
  push   %rbx
  sub    $0x68,%rsp
  mov    %rdi,-0x88(%rbp)
  mov    %rsi,-0x90(%rbp)
  mov    %fs:0x28,%rax
  mov    %rax,-0x38(%rbp)
  xor    %eax,%eax
  mov    %rsp,%rax
  mov    %rax,%rbx
  cmpq   $0x0,-0x88(%rbp)
  setne  %al
  movzbl %al,%eax
  mov    %eax,%edi
  call   <assert@plt>
  cmpq   $0x0,-0x90(%rbp)
  setne  %al
  movzbl %al,%eax
  mov    %eax,%edi
  call   <assert@plt>
  movq   $0x0,-0x80(%rbp)
  jmp    L158
L66:
  addq   $0x1,-0x80(%rbp)
L158:
  mov    -0x80(%rbp),%rax
  lea    0x0(,%rax,8),%rdx
  mov    -0x88(%rbp),%rax
  add    %rdx,%rax
  mov    (%rax),%rax
  test   %rax,%rax
  jne    L66
  cmpq   $0x0,-0x80(%rbp)
  jne    L111
  mov    $0x0,%eax
  jmp    L13
L111:
  mov    -0x80(%rbp),%rax
  mov    %rax,%rdx
  sub    $0x1,%rdx
  mov    %rdx,-0x58(%rbp)
  mov    %rax,%r14
  mov    $0x0,%r15d
  mov    %rax,%r12
  mov    $0x0,%r13d
  lea    0x0(,%rax,8),%rdx
  mov    $0x10,%eax
  sub    $0x1,%rax
  add    %rdx,%rax
  mov    $0x10,%esi
  mov    $0x0,%edx
  div    %rsi
  imul   $0x10,%rax,%rax
  mov    %rax,%rcx
  and    $0xfffffffffffff000,%rcx
  mov    %rsp,%rdx
  sub    %rcx,%rdx
L177:
  cmp    %rdx,%rsp
  je     L107
  sub    $0x1000,%rsp
  orq    $0x0,0xff8(%rsp)
  jmp    L177
L107:
  mov    %rax,%rdx
  and    $0xfff,%edx
  sub    %rdx,%rsp
  mov    %rax,%rdx
  and    $0xfff,%edx
  test   %rdx,%rdx
  je     L151
  and    $0xfff,%eax
  sub    $0x8,%rax
  add    %rsp,%rax
  orq    $0x0,(%rax)
L151:
  mov    %rsp,%rax
  add    $0x7,%rax
  shr    $0x3,%rax
  shl    $0x3,%rax
  mov    %rax,-0x50(%rbp)
  mov    -0x90(%rbp),%rax
  mov    %rax,%rdi
  call   <strlen@plt>
  mov    %rax,-0x48(%rbp)
  movq   $0x0,-0x78(%rbp)
  movq   $0x0,-0x70(%rbp)
  jmp    L102
L182:
  mov    -0x70(%rbp),%rax
  lea    0x0(,%rax,8),%rdx
  mov    -0x88(%rbp),%rax
  add    %rdx,%rax
  mov    (%rax),%rax
  test   %rax,%rax
  je     L114
  mov    -0x70(%rbp),%rax
  lea    0x0(,%rax,8),%rdx
  mov    -0x88(%rbp),%rax
  add    %rdx,%rax
  mov    (%rax),%rax
  mov    %rax,%rdi
  call   <strlen@plt>
  mov    -0x50(%rbp),%rdx
  mov    -0x70(%rbp),%rcx
  mov    %rax,(%rdx,%rcx,8)
  mov    -0x50(%rbp),%rax
  mov    -0x70(%rbp),%rdx
  mov    (%rax,%rdx,8),%rax
  add    %rax,-0x78(%rbp)
  mov    -0x80(%rbp),%rax
  sub    $0x1,%rax
  cmp    %rax,-0x70(%rbp)
  jae    L55
  mov    -0x48(%rbp),%rax
  add    %rax,-0x78(%rbp)
  jmp    L55
L114:
  nop
L55:
  addq   $0x1,-0x70(%rbp)
L102:
  mov    -0x70(%rbp),%rax
  cmp    -0x80(%rbp),%rax
  jb     L182
  mov    -0x78(%rbp),%rax
  add    $0x1,%rax
  mov    %rax,%rdi
  call   <malloc@plt>
  mov    %rax,-0x40(%rbp)
  cmpq   $0x0,-0x40(%rbp)
  jne    L135
  mov    $0x0,%eax
  jmp    L13
L135:
  mov    -0x40(%rbp),%rdx
  mov    -0x78(%rbp),%rax
  add    %rdx,%rax
  movb   $0x0,(%rax)
  mov    -0x40(%rbp),%rax
  mov    %rax,-0x68(%rbp)
  movq   $0x0,-0x60(%rbp)
  jmp    L126
L37:
  mov    -0x60(%rbp),%rax
  lea    0x0(,%rax,8),%rdx
  mov    -0x88(%rbp),%rax
  add    %rdx,%rax
  mov    (%rax),%rax
  test   %rax,%rax
  je     L49
  mov    -0x50(%rbp),%rax
  mov    -0x60(%rbp),%rdx
  mov    (%rax,%rdx,8),%rdx
  mov    -0x60(%rbp),%rax
  lea    0x0(,%rax,8),%rcx
  mov    -0x88(%rbp),%rax
  add    %rcx,%rax
  mov    (%rax),%rcx
  mov    -0x68(%rbp),%rax
  mov    %rcx,%rsi
  mov    %rax,%rdi
  call   <strncpy@plt>
  mov    -0x50(%rbp),%rax
  mov    -0x60(%rbp),%rdx
  mov    (%rax,%rdx,8),%rax
  add    %rax,-0x68(%rbp)
  mov    -0x80(%rbp),%rax
  sub    $0x1,%rax
  cmp    %rax,-0x60(%rbp)
  jae    L198
  mov    -0x48(%rbp),%rdx
  mov    -0x90(%rbp),%rcx
  mov    -0x68(%rbp),%rax
  mov    %rcx,%rsi
  mov    %rax,%rdi
  call   <strncpy@plt>
  mov    %rax,-0x68(%rbp)
  mov    -0x48(%rbp),%rax
  add    %rax,-0x68(%rbp)
  jmp    L198
L49:
  nop
L198:
  addq   $0x1,-0x60(%rbp)
L126:
  mov    -0x60(%rbp),%rax
  cmp    -0x80(%rbp),%rax
  jb     L37
  mov    -0x40(%rbp),%rax
L13:
  mov    %rbx,%rsp
  mov    -0x38(%rbp),%rdx
  sub    %fs:0x28,%rdx
  je     L148
  call   <__stack_chk_fail@plt>
L148:
  lea    -0x28(%rbp),%rsp
  pop    %rbx
  pop    %r12
  pop    %r13
  pop    %r14
  pop    %r15
  pop    %rbp
  ret
```

assistant: ```c
char *string_join(const char **strings, const char *sep) {
  assert(strings != NULL);
  assert(sep != NULL);
  size_t strings_count;
  for (strings_count = 0; strings[strings_count]; strings_count++)
    ;
  if (strings_count == 0)
    return NULL;
  size_t lengths[strings_count];
  size_t sep_len = strlen(sep);
  size_t len = 0;
  for (size_t i = 0; i < strings_count; i++) {
    if (!strings[i])
      continue;
    lengths[i] = strlen(strings[i]);
    len += lengths[i];
    if (i < strings_count - 1)
      len += sep_len;
  }
  char *result = malloc(len + 1);
  if (!result)
    return NULL;
  result[len] = 0;
  char *dst = result;
  for (size_t i = 0; i < strings_count; i++) {
    if (!strings[i])
      continue;
    strncpy(dst, strings[i], lengths[i]);
    dst += lengths[i];
    if (i < strings_count - 1) {
      dst = strncpy(dst, sep, sep_len);
      dst += sep_len;
    }
  }
  return result;
}
```