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

```asm
<main>:
  endbr64
  sub    $0x8,%rsp
  xor    %eax,%eax
  call   <_ensure_buffer_new_returns_null_when_given_null_allocator@plt>
  xor    %eax,%eax
  call   <_ensure_buffer_new_returns_null_when_allocation_fails@plt>
  xor    %eax,%eax
  call   <_ensure_buffer_new_initialises_buffer_with_zero_capacity@plt>
  xor    %eax,%eax
  call   <_ensure_buffer_new_initialises_buffer_with_zero_data_length@plt>
  xor    %eax,%eax
  call   <_ensure_buffer_delete_copes_with_null_buffer@plt>
  xor    %eax,%eax
  call   <_ensure_buffer_delete_copes_with_cleaned_up_buffer@plt>
  xor    %eax,%eax
  call   <_ensure_buffer_delete_releases_all_memory_consumed_by_legitimate_buffer@plt>
  xor    %eax,%eax
  call   <_ensure_buffer_init_initialises_buffer_with_zero_capacity@plt>
  xor    %eax,%eax
  call   <_ensure_buffer_init_initialises_buffer_with_zero_data_length@plt>
  xor    %eax,%eax
  call   <_ensure_buffer_init_copes_with_null_buffer@plt>
  xor    %eax,%eax
  call   <_ensure_buffer_init_copes_with_null_allocator@plt>
  xor    %eax,%eax
  call   <_ensure_buffer_init_copes_with_failed_allocation@plt>
  xor    %eax,%eax
  call   <_ensure_buffer_cleanup_copes_with_null_buffer@plt>
  xor    %eax,%eax
  call   <_ensure_buffer_cleanup_copes_with_cleaned_up_buffer@plt>
  xor    %eax,%eax
  call   <_ensure_buffer_cleanup_releases_all_memory_consumed_by_legitimate_buffer@plt>
  xor    %eax,%eax
  call   <_ensure_buffer_grow_increases_capacity_by_given_non_zero_amount@plt>
  xor    %eax,%eax
  call   <_ensure_buffer_grow_does_not_reallocate_when_given_zero_amount@plt>
  xor    %eax,%eax
  call   <_ensure_buffer_grow_returns_zero_when_given_length_of_zero_on_empty_buffer@plt>
  xor    %eax,%eax
  call   <_ensure_buffer_grow_returns_current_capacity_when_given_length_of_zero_on_nonempty_buffer@plt>
  xor    %eax,%eax
  call   <_ensure_buffer_grow_returns_correct_total_capacity_when_growing_empty_buffer@plt>
  xor    %eax,%eax
  call   <_ensure_buffer_grow_returns_correct_total_capacity_when_growing_non_empty_buffer@plt>
  xor    %eax,%eax
  call   <_ensure_buffer_grow_copes_with_null_buffer@plt>
  xor    %eax,%eax
  call   <_ensure_buffer_grow_copes_with_cleaned_up_buffer@plt>
  xor    %eax,%eax
  call   <_ensure_buffer_data_length_returns_exact_number_of_bytes_written_to_buffer@plt>
  xor    %eax,%eax
  call   <_ensure_buffer_data_length_copes_with_null_buffer@plt>
  xor    %eax,%eax
  call   <_ensure_buffer_data_length_copes_with_cleaned_up_buffer@plt>
  xor    %eax,%eax
  call   <_ensure_buffer_data_pointer_returns_null_for_empty_buffer@plt>
  xor    %eax,%eax
  call   <_ensure_buffer_data_pointer_copes_with_null_buffer@plt>
  xor    %eax,%eax
  call   <_ensure_buffer_data_pointer_copes_with_cleaned_up_buffer@plt>
  xor    %eax,%eax
  call   <_ensure_buffer_rewind_reuses_existing_buffer_capacity@plt>
  xor    %eax,%eax
  call   <_ensure_buffer_rewind_copes_with_empty_buffer@plt>
  xor    %eax,%eax
  call   <_ensure_buffer_rewind_copes_with_null_buffer@plt>
  xor    %eax,%eax
  call   <_ensure_buffer_rewind_copes_with_cleaned_up_buffer@plt>
  xor    %eax,%eax
  call   <_ensure_buffer_append_copies_given_data_into_buffer@plt>
  xor    %eax,%eax
  call   <_ensure_buffer_append_copes_with_null_buffer@plt>
  xor    %eax,%eax
  call   <_ensure_buffer_append_copes_with_cleaned_up_buffer@plt>
  xor    %eax,%eax
  call   <_ensure_buffer_append_does_not_mutate_buffer_when_given_zero_data_length@plt>
  xor    %eax,%eax
  call   <_ensure_buffer_append_does_not_mutate_buffer_when_given_null_data_pointer@plt>
  xor    %eax,%eax
  call   <_ensure_buffer_append_returns_number_of_bytes_appended_to_buffer@plt>
  xor    %eax,%eax
  call   <_ensure_buffer_reserve_copes_with_null_buffer@plt>
  xor    %eax,%eax
  call   <_ensure_buffer_reserve_copes_with_cleaned_up_buffer@plt>
  xor    %eax,%eax
  call   <_ensure_buffer_reserve_does_not_mutate_buffer_when_given_zero_data_length@plt>
  xor    %eax,%eax
  call   <_ensure_buffer_reserve_returns_non_null_pointer_on_success@plt>
  xor    %eax,%eax
  add    $0x8,%rsp
  ret
```

assistant: ```c
int main(int argc, char *argv[]) {
  (void)(argc);
  (void)(argv);
  _ensure_buffer_new_returns_null_when_given_null_allocator();
  _ensure_buffer_new_returns_null_when_allocation_fails();
  _ensure_buffer_new_initialises_buffer_with_zero_capacity();
  _ensure_buffer_new_initialises_buffer_with_zero_data_length();
  _ensure_buffer_delete_copes_with_null_buffer();
  _ensure_buffer_delete_copes_with_cleaned_up_buffer();
  _ensure_buffer_delete_releases_all_memory_consumed_by_legitimate_buffer();
  _ensure_buffer_init_initialises_buffer_with_zero_capacity();
  _ensure_buffer_init_initialises_buffer_with_zero_data_length();
  _ensure_buffer_init_copes_with_null_buffer();
  _ensure_buffer_init_copes_with_null_allocator();
  _ensure_buffer_init_copes_with_failed_allocation();
  _ensure_buffer_cleanup_copes_with_null_buffer();
  _ensure_buffer_cleanup_copes_with_cleaned_up_buffer();
  _ensure_buffer_cleanup_releases_all_memory_consumed_by_legitimate_buffer();
  _ensure_buffer_grow_increases_capacity_by_given_non_zero_amount();
  _ensure_buffer_grow_does_not_reallocate_when_given_zero_amount();
  _ensure_buffer_grow_returns_zero_when_given_length_of_zero_on_empty_buffer();
  _ensure_buffer_grow_returns_current_capacity_when_given_length_of_zero_on_nonempty_buffer();
  _ensure_buffer_grow_returns_correct_total_capacity_when_growing_empty_buffer();
  _ensure_buffer_grow_returns_correct_total_capacity_when_growing_non_empty_buffer();
  _ensure_buffer_grow_copes_with_null_buffer();
  _ensure_buffer_grow_copes_with_cleaned_up_buffer();
  _ensure_buffer_data_length_returns_exact_number_of_bytes_written_to_buffer();
  _ensure_buffer_data_length_copes_with_null_buffer();
  _ensure_buffer_data_length_copes_with_cleaned_up_buffer();
  _ensure_buffer_data_pointer_returns_null_for_empty_buffer();
  _ensure_buffer_data_pointer_copes_with_null_buffer();
  _ensure_buffer_data_pointer_copes_with_cleaned_up_buffer();
  _ensure_buffer_rewind_reuses_existing_buffer_capacity();
  _ensure_buffer_rewind_copes_with_empty_buffer();
  _ensure_buffer_rewind_copes_with_null_buffer();
  _ensure_buffer_rewind_copes_with_cleaned_up_buffer();
  _ensure_buffer_append_copies_given_data_into_buffer();
  _ensure_buffer_append_copes_with_null_buffer();
  _ensure_buffer_append_copes_with_cleaned_up_buffer();
  _ensure_buffer_append_does_not_mutate_buffer_when_given_zero_data_length();
  _ensure_buffer_append_does_not_mutate_buffer_when_given_null_data_pointer();
  _ensure_buffer_append_returns_number_of_bytes_appended_to_buffer();
  _ensure_buffer_reserve_copes_with_null_buffer();
  _ensure_buffer_reserve_copes_with_cleaned_up_buffer();
  _ensure_buffer_reserve_does_not_mutate_buffer_when_given_zero_data_length();
  _ensure_buffer_reserve_returns_non_null_pointer_on_success();
  return 0;
}
```