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I heard that it is possible to use unicode variable names using the -fextended-identifiers flag in gcc. So I made a test program in C++ but it does not compile.
#include <iostream>
#include <string>
#define ¬ !
#define ≠ !=
#define « <<
#define » >>
/* uniq: remove duplicate lines from stdin */
int main() {
std::string s;
std::string t = "";
while (cin » s) {
if (s ≠ t)
cout « s;
t = s;
}
return 0;
}
I get these errors:
g++ -fextended-identifiers -g3 -o a main.cpp
main.cpp:10:3: error: stray ‘\342’ in program
if (s ≠ t)
^
main.cpp:10:3: error: stray ‘\211’ in program
main.cpp:10:3: error: stray ‘\240’ in program
main.cpp:11:4: error: stray ‘\302’ in program
cout « s;
^
main.cpp:11:4: error: stray ‘\253’ in program
What is going on? Aren't these macro names supposed to work with -fextended-identifiers?
The C++ Standard requires (section 2.10):
An identifier is an arbitrarily long sequence of letters and digits. Each universal-character-name in an identifier shall designate a character whose encoding in ISO 10646 falls into one of the ranges specified in E.1. The initial element shall not be a universal-character-name designating a character whose encoding falls into one of the ranges specified in E.2. Upper- and lower-case letters are different. All characters are significant.
And E.1:
Ranges of characters allowed [charname.allowed]
00A8, 00AA, 00AD, 00AF, 00B2-00B5, 00B7-00BA, 00BC-00BE, 00C0-00D6, 00D8-00F6, 00F8-00FF
0100-167F, 1681-180D, 180F-1FFF
200B-200D, 202A-202E, 203F-2040, 2054, 2060-206F
2070-218F, 2460-24FF, 2776-2793, 2C00-2DFF, 2E80-2FFF
3004-3007, 3021-302F, 3031-303F
3040-D7FF
F900-FD3D, FD40-FDCF, FDF0-FE44, FE47-FFFD
10000-1FFFD, 20000-2FFFD, 30000-3FFFD, 40000-4FFFD, 50000-5FFFD,
60000-6FFFD, 70000-7FFFD, 80000-8FFFD, 90000-9FFFD, A0000-AFFFD,
B0000-BFFFD, C0000-CFFFD, D0000-DFFFD, E0000-EFFFD
0300-036F, 1DC0-1DFF, 20D0-20FF, FE20-FE2F
Your angle brackets are 0x300A and 0x300B, which are not included. Not equal is 0x2260, also disallowed.
G++ doesn't support Unicode characters in the source yet:
- What is the status of adding the UTF-8 support for identifier names in GCC?
Notably, the errors generated by your program are for the individual octets of the UTF-8 encoding, not for the Unicode character they represent. ≠ is being seen as three bytes: \342\211\240 and « as two: \302\253.
