Re: [Libvir] [PATCH] Enhance virBuffer code

Jim Meyering wrote: > "Richard W.M. Jones" <rjones(a)redhat.com&gt; 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.