[Libvir] [PATCH] Enhance virBuffer code

[Richard W.M. Jones]

Jim Meyering wrote:
> "Richard W.M. Jones" <rjones at redhat.com> wrote:
>> Jim Meyering wrote:
>>> What do you think of using this?
>>>
>>>   isascii (*p) && isalnum (*p)
>> I'm not sure I'm qualified to say what this does on EBCDIC, but quite
>> likely lots of other code breaks there too anyway.  This is nicely
>> self-documenting anyway.
> 
> As Daniel suggested, isalnum is locale-sensitive.
> If there's a locale with an alphabetic byte that is outside
> the logical a-zA-Z range, yet still within 0..127, then the above
> expression will give a false-positive for that byte.
> 
> I've been inclined to stop worrying about EBCDIC for years, but a quick
> search on the web finds that people are still stuck using it, and do
> report bugs in ASCII-assuming code.
> 
> This is why autoconf goes to the trouble of doing this:
>   tr abcdefghijklmnopqrstuvwxyz ABCDEFGHIJKLMNOPQRSTUVWXYZ
> not this:
>   tr a-z A-Z
> to convert to upper case.

Another factor to consider here is that it doesn't matter if this 
function over-escapes, but it does matter if the function under-escapes. 
  That is to say, it could escape every character as a %xx hex code, 
which would be ugly and slightly inefficient but not wrong.

Rich.

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