Re: [PATCH] gdb: add UTF16/UTF32 target charsets in phony_iconv

[Tom Tromey <tom@tromey.com>]

>> I don't recall the outcome from this, but is there no way to improve gdb
>> to use this iconv?  If it truly works well enough then it seems like it
>> would be the better approach.

Patrick> There is a fuzzy source comment about an iconv problem in
Patrick> Solaris. Your bugzilla comment 
Patrick> https://sourceware.org/bugzilla/show_bug.cgi?id=29315#c2 also goes in
Patrick> this direction: however we have no details about what the problem is,
Patrick> if we should still support it and/or if there are other systems
Patrick> affected by such an iconv problem.

Ok.  Thank you for the link, I knew we had discussed this somewhere in
the past...

The comments at the top of gdb_wchar.h describe the situation somewhat,
though they don't really explain what was wrong with Solaris.  My
recollection, though, is that the Solaris wchar_t doesn't have any
ordinary encoding but is instead a weird hybrid thing, and furthermore
that the Solaris iconv doesn't accept "wchar_t" as an encoding name.
So, on Solaris, there's no convenient way to do the conversions (it's
possible to convert wchar_t to/from the locale's multi-byte encoding,
but I didn't implement that since it seemed like a pain).

All of this is based on the idea that it's convenient to work in a wide
character representation at some points in the code.  At the time, I
figured relying on wchar_t would be good for this because (presumably)
hosts would support that reasonably well and we wouldn't have to do
extra work in gdb.

However, it seems to me that it doesn't really have to be done this way.
We could use UTF-32 instead, by making our own tables (along the lines
of ada-unicode.py) for "isdigit" and "isprint".

In addition to this, I suppose we could simply require iconv.  Probably
any host that has iconv will support UTF-32 (if not, what good is it
really).  And libiconv exists and can even be conveniently dropped into
the source tree if there are any hosts that don't have it.  This may not
be a good plan if there are active host platforms where this would be a
pain to deal with.

Anyway, what do you think of this plan?

Patrick> Please note I had the intention to determine the Solaris problem and
Patrick> tried to install the last available OpenSolaris (dated 2009) in a VM 
Patrick> without success: I gave up.

Yeah, that's fine, I wouldn't have done it myself.

Tom