Re: [RFA] Handle cygwin wchar_t specifics

[Tom Tromey <tromey at redhat dot com>]

>>>>> "Pierre" == Pierre Muller <pierre.muller@ics-cnrs.unistra.fr> writes:

Pierre> because of this, GDB uses "UCS-4LE" 
Pierre> for the macro INTERMEDIATE_ENCODING on Cygwin 
Pierre> (while "wchar_t" it uses for mingw32, which works well).

Ok, I see the problem.  I thought this:

    /* If __STDC_ISO_10646__ is defined, then the host wchar_t is UCS-4.

But this is not true!  For some values of __STDC_ISO_10646__, a 2 byte
wide character type suffices.  In particular, Cygwin's value of 200305
means that it corresponds to Unicode 4.0.0:

    http://www.unicode.org/versions/components-4.0.0.html

I think this might be a Cygwin bug, but it is pretty hard to wade
through the ISO / Unicode differences and other assorted standardese to
see.  (The reason I think it might be a bug is that Unicode 4.0.0
defines some characters > 0xFFFF.)

Anyway, it doesn't matter if this is a Cygwin bug, since GDB's
assumption here is wrong anyway.

Pierre> The patch below fixes this by
Pierre> explicitly setting the UCS size to two for Windows targets.

I think in the __STDC_ISO_10646__ case, we should just explicitly use
sizeof (wchar_t) somewhere to choose the intermediate encoding.  I think
this will be more robust than testing some host define.

Pierre> +#define wchar_size  (&(((wchar_t) (0)) + 1) - &((char *) 0))

This doesn't seem to be used.

Tom