[Bug c++/59873] New: The value of char32_t U'\u0000' and char16_t u'\u000' is 1, instead of 0.

[wjl at icecavern dot net]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59873

            Bug ID: 59873
           Summary: The value of char32_t U'\u0000' and char16_t u'\u000'
                    is 1, instead of 0.
           Product: gcc
           Version: 4.8.3
            Status: UNCONFIRMED
          Severity: major
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: wjl at icecavern dot net

I found a major bug with char32_t and char16_t literals when trying to encode a
U+0000 (Null).

The following expressions have the numeric value 1, instead of the correct
value, 0. This makes it impossible to use code which has these literals.

The following typescript shows a program that demonstrates the problem, and
shows the behavior of g++ (incorrect) vs. clang++ (correct):

$ cat test.c++ 
#include <cstdint>
#include <iostream>

int main() {
    char32_t null = U'\u0000';
    std::cerr << "null (char32_t) = " << null << '\n';
    std::cerr << "null (uint32_t) = " << uint32_t(null) << '\n';

    char32_t soh = U'\u0001';
    std::cerr << "soh (char32_t) = " << soh << '\n';
    std::cerr << "soh (uint32_t) = " << uint32_t(soh) << '\n';

    std::cerr << "char32_t null == soh = " << (U'\u0000' == U'\u0001') << '\n';

    char16_t null16 = u'\u0000';
    std::cerr << "null (char16_t) = " << null16 << '\n';
    std::cerr << "null (uint16_t) = " << uint16_t(null16) << '\n';

    char16_t soh16 = u'\u0001';
    std::cerr << "soh (char16_t) = " << soh16 << '\n';
    std::cerr << "soh (uint16_t) = " << uint16_t(soh16) << '\n';

    std::cerr << "char16_t null == soh = " << (u'\u0000' == u'\u0001') << '\n';
}
$ g++ --version
g++ (Debian 4.8.2-10) 4.8.2
Copyright (C) 2013 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

$ g++ -Wall -Wextra -std=c++11 test.c++
$ ./a.out
null (char32_t) = 1
null (uint32_t) = 1
soh (char32_t) = 1
soh (uint32_t) = 1
char32_t null == soh = 1
null (char16_t) = 1
null (uint16_t) = 1
soh (char16_t) = 1
soh (uint16_t) = 1
char16_t null == soh = 1
$ clang++ --version
Debian clang version 3.5-1 (trunk) (based on LLVM 3.5)
Target: x86_64-pc-linux-gnu
Thread model: posix
$ clang++ -Wall -Wextra -std=c++11 test.c++ 
$ ./a.out 
null (char32_t) = 0
null (uint32_t) = 0
soh (char32_t) = 1
soh (uint32_t) = 1
char32_t null == soh = 0
null (char16_t) = 0
null (uint16_t) = 0
soh (char16_t) = 1
soh (uint16_t) = 1
char16_t null == soh = 0