r201715 - Moving the documentation for the clang::fallthrough attribute into AttrDocs.

[Richard Smith]

On Wed, Feb 19, 2014 at 12:56 PM, Aaron Ballman <aaron at aaronballman.com>wrote:

> Author: aaronballman
> Date: Wed Feb 19 14:56:51 2014
> New Revision: 201715
>
> URL: http://llvm.org/viewvc/llvm-project?rev=201715&view=rev
> Log:
> Moving the documentation for the clang::fallthrough attribute into
> AttrDocs.
>
> Modified:
>     cfe/trunk/docs/LanguageExtensions.rst
>     cfe/trunk/include/clang/Basic/Attr.td
>     cfe/trunk/include/clang/Basic/AttrDocs.td
>
> Modified: cfe/trunk/docs/LanguageExtensions.rst
> URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/docs/LanguageExtensions.rst?rev=201715&r1=201714&r2=201715&view=diff
>
> ==============================================================================
> --- cfe/trunk/docs/LanguageExtensions.rst (original)
> +++ cfe/trunk/docs/LanguageExtensions.rst Wed Feb 19 14:56:51 2014
> @@ -1570,51 +1570,6 @@ Non-standard C++11 Attributes
>  Clang's non-standard C++11 attributes live in the ``clang`` attribute
>  namespace.
>
> -The ``clang::fallthrough`` attribute
> -------------------------------------
> -
> -The ``clang::fallthrough`` attribute is used along with the
> -``-Wimplicit-fallthrough`` argument to annotate intentional fall-through
> -between switch labels.  It can only be applied to a null statement placed
> at a
> -point of execution between any statement and the next switch label.  It is
> -common to mark these places with a specific comment, but this attribute is
> -meant to replace comments with a more strict annotation, which can be
> checked
> -by the compiler.  This attribute doesn't change semantics of the code and
> can
> -be used wherever an intended fall-through occurs.  It is designed to mimic
> -control-flow statements like ``break;``, so it can be placed in most
> places
> -where ``break;`` can, but only if there are no statements on the
> execution path
> -between it and the next switch label.
> -
> -Here is an example:
> -
> -.. code-block:: c++
> -
> -  // compile with -Wimplicit-fallthrough
> -  switch (n) {
> -  case 22:
> -  case 33:  // no warning: no statements between case labels
> -    f();
> -  case 44:  // warning: unannotated fall-through
> -    g();
> -    [[clang::fallthrough]];
> -  case 55:  // no warning
> -    if (x) {
> -      h();
> -      break;
> -    }
> -    else {
> -      i();
> -      [[clang::fallthrough]];
> -    }
> -  case 66:  // no warning
> -    p();
> -    [[clang::fallthrough]]; // warning: fallthrough annotation does not
> -                            //          directly precede case label
> -    q();
> -  case 77:  // warning: unannotated fall-through
> -    r();
> -  }
> -
>  ``gnu::`` attributes
>  --------------------
>

This change has left the remaining text here a bit broken: "Clang also
supports GCC's gnu attribute namespace [...]".

Modified: cfe/trunk/include/clang/Basic/Attr.td
> URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Basic/Attr.td?rev=201715&r1=201714&r2=201715&view=diff
>
> ==============================================================================
> --- cfe/trunk/include/clang/Basic/Attr.td (original)
> +++ cfe/trunk/include/clang/Basic/Attr.td Wed Feb 19 14:56:51 2014
> @@ -642,7 +642,7 @@ def ExtVectorType : Attr {
>  def FallThrough : Attr {
>    let Spellings = [CXX11<"clang", "fallthrough">];
>  //  let Subjects = [NullStmt];
> -  let Documentation = [Undocumented];
> +  let Documentation = [FallthroughDocs];
>  }
>
>  def FastCall : InheritableAttr {
>
> Modified: cfe/trunk/include/clang/Basic/AttrDocs.td
> URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Basic/AttrDocs.td?rev=201715&r1=201714&r2=201715&view=diff
>
> ==============================================================================
> --- cfe/trunk/include/clang/Basic/AttrDocs.td (original)
> +++ cfe/trunk/include/clang/Basic/AttrDocs.td Wed Feb 19 14:56:51 2014
> @@ -410,3 +410,50 @@ When one method overrides another, the o
>    @end
>    }];
>  }
> +
> +def FallthroughDocs : Documentation {
> +  let Category = DocCatStmt;
> +  let Content = [{
> +The ``clang::fallthrough`` attribute is used along with the
> +``-Wimplicit-fallthrough`` argument to annotate intentional fall-through
> +between switch labels.  It can only be applied to a null statement placed
> at a
> +point of execution between any statement and the next switch label.  It is
> +common to mark these places with a specific comment, but this attribute is
> +meant to replace comments with a more strict annotation, which can be
> checked
> +by the compiler.  This attribute doesn't change semantics of the code and
> can
> +be used wherever an intended fall-through occurs.  It is designed to mimic
> +control-flow statements like ``break;``, so it can be placed in most
> places
> +where ``break;`` can, but only if there are no statements on the
> execution path
> +between it and the next switch label.
> +
> +Here is an example:
> +
> +.. code-block:: c++
> +
> +  // compile with -Wimplicit-fallthrough
> +  switch (n) {
> +  case 22:
> +  case 33:  // no warning: no statements between case labels
> +    f();
> +  case 44:  // warning: unannotated fall-through
> +    g();
> +    [[clang::fallthrough]];
> +  case 55:  // no warning
> +    if (x) {
> +      h();
> +      break;
> +    }
> +    else {
> +      i();
> +      [[clang::fallthrough]];
> +    }
> +  case 66:  // no warning
> +    p();
> +    [[clang::fallthrough]]; // warning: fallthrough annotation does not
> +                            //          directly precede case label
> +    q();
> +  case 77:  // warning: unannotated fall-through
> +    r();
> +  }
> +  }];
> +}
>
>
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