Re: quotearg improvements [was: filenames in error messages]

[Karl Berry]

    Consider the original filename of `dir??/file'.  

Thanks, I see now.

Now I think rms's implicit desire not to map this too strongly to C
strings is a a good thing.  The goal is to make it easy/unambiguous for
programs like Emacs to parse the filenames out of the message.  Doing
full parsing of C strings is not exactly easy, as evidenced by the
above.  And for the present situation, the complications are unnecessary
-- ? is not a problematic character for parsing the error message.  So I
think the ideal would be an original filename of `dir??/file' to be
output as exactly that: dir??/file.  I see no need even for quotes
(although they could be present, then we'd have "dir??/file").

So the biggest issues are newlines and : characters, both of which
you've already dealt with.  For completeness, we'll handle other control
characters, and we'll have to handle \ and " themselves of course.  Are
there any other chars that can be troublesome for next-error (or
whatever tool)?  I can't see any, but wdyt?

As for shell special chars like space and ? and * and [], I don't see
how they would interfere with next-error parsing the messages, so I'd
say none of them should be considered special for this purpose.

In a nutshell, if the source file name contains : or \ or " or any
control character, we enclose it in quotes and escape as needed.
Otherwise, no quotes needed.  Wdyt?

Sorry for not realizing the whole trigraph complication.

Thanks,
karl