[Geany-devel] Changed file saving implementation for systems with GIO

[Nick Treleaven]

On Sat, 6 Nov 2010 11:33:41 +0200
Dimitar Zhekov <dimitar.zhekov at gmail.com> wrote:

> I'll write a non-GIO variant first, as a proof of concept.

First, I feel quite reluctant to use non-GLib/GIO functions for writing
instead of g_file_replace_contents because if there is a better
implementation, why don't they add it?

Also, g_file_replace_contents does have a make_backup argument we could
provide an option for. This might handle the disk exhaustion problem.

> The current non-GIO is buggy anyway. First:
> 
> if (G_UNLIKELY(len != bytes_written))
>         err = errno;
> 
> but fwrite() is not guaranteed to set errno, only write() is.
> 
> Second, and more important, the result of fclose() is not checked, for
> a buffered file stream. On lack of disk space, on my system fwrite()
> happily returns written == len, but fclose() fails. YMMV.
> 
> If not anything else, we should use non-buffered I/O, with fsync(), and
> check the result of close() anyway.

Thanks for finding these problems. I accept fclose should be checked.

I'm not sure why write is better than fwrite - POSIX says both set
errno.
http://www.opengroup.org/onlinepubs/009695399/functions/fwrite.html

Can you explain why non-buffered I/O is better?

Nick

P.S. Thanks for sending the updated patch.