[Bug c++/50941] New: [C++0x] user-defined string literals provide incorrect length for wchar_t, char16_t, and char32_t

[daniel.kruegler at googlemail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50941

             Bug #: 50941
           Summary: [C++0x] user-defined string literals provide incorrect
                    length for wchar_t, char16_t, and char32_t
    Classification: Unclassified
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: daniel.kruegler@googlemail.com
                CC: jason@redhat.com


gcc 4.7.0 20111029 (experimental) in C++0x mode rejects the following code:

//---
typedef decltype(sizeof(0)) size_type;

constexpr size_type operator "" _len(const char*, size_type len)
{
  return len;
}

constexpr size_type operator "" _len(const wchar_t*, size_type len)
{
  return len;
}

constexpr size_type operator "" _len(const char16_t*, size_type len)
{
  return len;
}

constexpr size_type operator "" _len(const char32_t*, size_type len)
{
  return len;
}

static_assert(  ""_len == 0, "Ouch"); // OK
static_assert(u8""_len == 0, "Ouch"); // OK
static_assert( L""_len == 0, "Ouch"); // Error
static_assert( u""_len == 0, "Ouch"); // Error
static_assert( U""_len == 0, "Ouch"); // Error
//---

With 

"error: static assertion failed: "Ouch"" 

at the marked lines.

The code should be accepted.

It turns out that for wchar_t, char16_t, and char32_t string literals the
provided length is 1, not 0. But according to N3290 2.14.8 p5 and 2.14.5 p15
the provided length value should also be 0 in above examples. This problem also
occurs for non-empty strings: The length value is always too large by 1 for the
mentioned string types.