Update of "GCC extensions not implemented yet" in Clang User's Manual

[andreybokhanko]

Summary

#pragma weak, global register variables and static initialization of flexible array members are supported, so I removed them from "GCC extensions not implemented yet" list.

[andreybokhanko]

Ping

[silvas]

Assuming the features are implemented this seems fine. LGTM.

docs/UsersManual.rst

1698

Should we close that bug then?

[andreybokhanko]

In D16851#349537, @silvas wrote:

Assuming the features are implemented this seems fine. LGTM.

Thank you!

docs/UsersManual.rst

1698

As often happens, this bug started as a general feature request ("pragma weak doesn't work at all"), but the last few messages just report a specific defect in a specific case and keep the PR open.

I will ask one of our (Intel) engineers to take a look and either close the PR if the bug is already fixed or fix it otherwise.

Andrey

docs/UsersManual.rst

 c94 mode (FIXME: And ``__STDC_VERSION__`` should be defined!).
 
 GCC extensions not implemented yet
 ----------------------------------
 
 clang tries to be compatible with gcc as much as possible, but some gcc
 extensions are not implemented yet:
 
--  clang does not support #pragma weak (`bug
-   3679 <http://llvm.org/bugs/show_bug.cgi?id=3679>`_). Due to the uses
-   described in the bug, this is likely to be implemented at some point,
-   at least partially.
 -  clang does not support decimal floating point types (``_Decimal32`` and
    friends) or fixed-point types (``_Fract`` and friends); nobody has
    expressed interest in these features yet, so it's hard to say when
    they will be implemented.
 -  clang does not support nested functions; this is a complex feature
    which is infrequently used, so it is unlikely to be implemented
    anytime soon. In C++11 it can be emulated by assigning lambda
    functions to local variables, e.g:
 
    .. code-block:: cpp
 
      auto const local_function = [&](int parameter) {
        // Do something
      };
      ...
      local_function(1);
 
--  clang does not support global register variables; this is unlikely to
-   be implemented soon because it requires additional LLVM backend
-   support.
--  clang does not support static initialization of flexible array
-   members. This appears to be a rarely used extension, but could be
-   implemented pending user demand.
 -  clang does not support
    ``__builtin_va_arg_pack``/``__builtin_va_arg_pack_len``. This is
    used rarely, but in some potentially interesting places, like the
    glibc headers, so it may be implemented pending user demand. Note
    that because clang pretends to be like GCC 4.2, and this extension
    was introduced in 4.3, the glibc headers will not try to use this
    extension with clang at the moment.
 -  clang does not support the gcc extension for forward-declaring