Re: special characters in filenames in error messages

[Karl Berry]

    Therefore, when you deal with an URI, you should use a different
    algorithm of presentation within a GNU error message than when you
    deal with a filename.

This seems like it adds complexity both in the description and in
comprehension.  At least I am having trouble with it -- it seems like %
now means two different things, and a program has to know in advance
whether the source is a url or a filename.  I am rather doubtful rms
would be happy with it.

As an alternative, we could simply use a different character than % for
our filename hex escape.  Two that come to mind are ! (already a shell
metachar, unusual in filenames, not special in url's) and " itself.
Since : is not a hex digit, there is no ambiguity, I believe -- you just
have to search for ": to find the end of the escaped source name.  And %
always means %.

filename:line  ! escape            " escape
--------       -----------         --------
a"b\nc%d:10    "a!22b!0ac%d":10    "a"22b"0ac%d":10
(where \n is 
a real newline)

Despite the superficial ambiguity, using " seems somehow cleaner to me,
since it reduces special characters to the absolute minimum of one.
(BTW, TeX uses " to introduce hex constants in some contexts.  Not that
that matters, I admit.)

Wdyt?

Thanks,
karl