Re: [PATCH] libpoke/ios-dev-stream.c: free buffer only in read mode

[Mohammad-Reza Nabipoor]

Hi, Jose.

On Sat, Oct 17, 2020 at 12:23:12PM +0200, Jose E. Marchesi wrote:
> 
> Wouldn't it be better to make sure to initialize sio->buffer to NULL
> when it is not used, and then to either:
>

Currently the `buffer` field is inside an anonymous union (and shares the
storage with `uint64_t write_offset`).
If we want to check the nullability, we should remove the `union`.

Like this:

```c
struct ios_dev_stream
{
  char *handler;
  FILE *file;
  uint64_t flags;
  struct ios_buffer *buffer;
  uint64_t write_offset;
};
```

> 
> 1. Document (in ios-buffer.h) that ios_buffer_free works as a nop if
>    NULL is passed, or
> 
> 2. Check for sio->buffer == NULL in ios_dev_stream_close and call (or
>    not) ios_buffer_free accordingly.
> 

I prefer the option 2 (plus adding an explicit pre-condition that `buffer` must
be non-null).

But I guess option 1 is more popular among C programmers.


WDYT?
Should I remove the `union`?
Which approach do you think is the best for `ios_buffer_free(NULL)`?
NOP or assertion?


Regards,
Mohammad-Reza