g++ unicode variable name - unicode

Question

I am trying to use unicode variable names in g++.
It does not appear to work.
Does g++ not support unicode variable names, ... or is there some subset of unicode (from which I'm not testing in).
Thanks!

Answer 1

You have to specify the -fextended-identifiers flag when compiling, you also have to use \uXXXX or \uXXXXXXXX for unicode(atleast in gcc it's unicode)
Identifiers (variable/class names etc) in g++ can't be of utf-8/utf-16 or whatever encoding,
they have to be:
identifier:
nondigit
identifier nondigit
identifier digit
a nondigit is
nondigit: one of
universalcharactername
_ a b c d e f g h i j k l m n o p q r s t u v w x y z
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
and a universalcharactername is
universalcharactername:
\UXXXXXXXX
\uXXXX
Thus, if you save your source file as UTF-8, you cannot have a variable like e.g.:
int høyde = 10;
it had to be written like:
int h\u00F8yde = 10;
(which imo would beat the whole purpose - so just stick with a-z)

Answer 2

A one-line patch to the cpp preprocessor allows UTF-8 input. Details for gcc are given at
https://www.raspberrypi.org/forums/viewtopic.php?p=802657
however, since the preprocessor is shared, the same patch should work for g++ as well. In particular, the patch needed, as of gcc-5.2 is
diff -cNr gcc-5.2.0/libcpp/charset.c gcc-5.2.0-ejo/libcpp/charset.c
*** gcc-5.2.0/libcpp/charset.c Mon Jan 5 04:33:28 2015
--- gcc-5.2.0-ejo/libcpp/charset.c Wed Aug 12 14:34:23 2015
***************
*** 1711,1717 ****
struct _cpp_strbuf to;
unsigned char *buffer;
! input_cset = init_iconv_desc (pfile, SOURCE_CHARSET, input_charset);
if (input_cset.func == convert_no_conversion)
{
to.text = input;
--- 1711,1717 ----
struct _cpp_strbuf to;
unsigned char *buffer;
! input_cset = init_iconv_desc (pfile, "C99", input_charset);
if (input_cset.func == convert_no_conversion)
{
to.text = input;
Note that for the above patch to work, a recent version of iconv needs to be installed that supports C99 conversions. Type iconv --list to verify this, otherwise, you can install a new version of iconv along with gcc as described in the link above. Change the configure command to
$ ../gcc-5.2.0/configure -v --disable-multilib \
--with-libiconv-prefix=/usr/local/gcc-5.2 \
--prefix=/usr/local/gcc-5.2 \
--enable-languages="c,c++"
if you are building for x86 and want to include the c++ compiler as well.