We always use UTF-8, meaning that a single `wchar_t` might be converted
into up to 4 `char`s. This would cause a buffer overflow if something
actually relied on this being the right value.
The C standard states that these symbols should be declared as macros,
not as emum variants as we were doing previously. This is used in some
ports (e.g. bash) to conditionally compile locale-dependent
functionality.
We now use the same trick here as with the errno constants. We keep the
enum, but also create macros that defer to the enum variants.
The `wcsxfrm` function copies a wide character string into a buffer,
such that comparing the new string against any similarly pre-processed
string with `wcscmp` produces the same result as if the original strings
were compared with `wcscoll`.
Our current `wcscoll` implementation is simply an alias for `wcscmp`, so
`wcsxfrm` needs to perform no actions other than copying the string.
The ELAST macro is used on many systems to refer to the largest possible
valid errno value. LLVM's libc++ uses errno values of ELAST+1 and
ELAST+2 internally, and defines an arbitrary fallback value for
platforms which don't have the macro. This means that it's possible for
their internal errno numbers could coincide with values we actually use,
which would be a very bad thing.
This function converts a single wide character into its multibyte
representation (UTF-8 in our case). It is called from libc++'s
`std::basic_ostream<wchar_t>::flush`, which gets called at program exit
from a global destructor in order to flush `std::wcout`.
In QtCreator (and under weird configurations with gcc), this used to
fail with the error messages like: "error: member of anonymous union
redeclares '___'".
This patch gives each member a unique name.
A zero-initialized mbstate_t struct has to be a valid initial state, so
we can just zero-initialize it whenever we need to reset.
Having a helper function for resetting the struct might imply that you
can add additional setup operations afterwards, which is not the case.
