On 2016-08-22 14:23, Eli Zaretskii wrote:
>> From: "Paul A. Steckler" <steck@stecksoft.com>
>> Date: Mon, 22 Aug 2016 13:35:25 -0400
>>
>> The documentation for Process Filter Functions mentions that process
>> filters receive the standard output from their associated processes. It
>> does not mention that the filters also receive standard error output.
> 
> That is described in the parent section:
> 
>      It is impossible to separate the standard output and standard error
>   streams of the subprocess, because Emacs normally spawns the subprocess
>   inside a pseudo-TTY, and a pseudo-TTY has only one output channel.  If
>   you want to keep the output to those streams separate, you should
>   redirect one of them to a file—for example, by using an appropriate
>   shell command.

Still, even the parent section could be confusing:

       The output that a subprocess writes to its standard output stream is
                                                  ^^^^^^^^^^^^^^^
    passed to a function called the “filter function”.  The default filter
    function simply inserts the output into a buffer, which is called the
    associated buffer of the process (*note Process Buffers::).  If the process
    has no buffer then the default filter discards the output.

The highlighted section is not true, is it?

Clément.