Re: printing wchar_t*

[Eli Zaretskii <eliz at gnu dot org>]

> From:  Vladimir Prus <ghost@cs.msu.su>
> Date:  Fri, 14 Apr 2006 10:01:57 +0400
> 
> > What character set is used by the wide characters in the wchar_t
> > arrays?  GDB has some support for a few single-byte character sets,
> > see the node "Character Sets" in the manual.
> 
> Relatively safe bet would be to assume it's some zero-terminated character
> set. I plan to assume it's either UTF-16 or UTF-32 in the GUI (the
> conversion code is the same for both encodings), but gdb can just print raw
> values.

We should get our terminology right: UTF-16 is not a character set,
it's an encoding (and a multibyte encoding, btw).  As for UTF-32, I
don't think such a beast exists at all.

I think you meant 16-bit Unicode characters (a.k.a. the BMP) and
32-bit Unicode characters, respectively.

> > It's one possibility, the other one being to call a function in the
> > debuggee to produce the string. 
> 
> And what such a function will return? char* in local 8-bit encoding? In that
> case, no all wchar_t* variable can be printed.

If you want to display non-ASCII strings, it means you already have
some way of displaying such characters.  The function I mentioned
would not return anything, it would actually _display_ the string.

For example, in command-line version of GDB, if the terminal supports
UTF-8 encoded characters, that function would output a UTF-8 encoding
of the non-ASCII string, and then the terminal will display them with
the correct glyphs.

> > Yet another possibility is to do the 
> > conversion in your GUI front end.
> 
> That's what I'm going to do, but first I need to get raw data, preferrably
> without issing an MI command for every single character.

A wchar_t string is just an array, and GDB already has a feature to
produce N elements of an array.  In CLI, you say "print *array@20" to
print the first 20 elements of the named array.