Author: aaronballman
Date: Tue Nov 20 07:23:07 2018
New Revision: 347312
URL: http://llvm.org/viewvc/llvm-project?rev=347312&view=rev
Log:
Update the documentation for attribute feature tests.
This clarifies that __has_cpp_attribute is no longer always an extension since
it's now available in C++2a. Also, Both __has_cpp_attribute and
__has_c_attribute can accept attribute scope tokens with alternative spelling
(clang vs _Clang and gnu vs __gnu__).
Modified:
cfe/trunk/docs/LanguageExtensions.rst
Modified: cfe/trunk/docs/LanguageExtensions.rst
URL:
http://llvm.org/viewvc/llvm-project/cfe/trunk/docs/LanguageExtensions.rst?rev=347312&r1=347311&r2=347312&view=diff
==============================================================================
--- cfe/trunk/docs/LanguageExtensions.rst (original)
+++ cfe/trunk/docs/LanguageExtensions.rst Tue Nov 20 07:23:07 2018
@@ -112,18 +112,22 @@ of ``cxx_rvalue_references``.
``__has_cpp_attribute``
-----------------------
-This function-like macro takes a single argument that is the name of a
-C++11-style attribute. The argument can either be a single identifier, or a
-scoped identifier. If the attribute is supported, a nonzero value is returned.
-If the attribute is a standards-based attribute, this macro returns a nonzero
-value based on the year and month in which the attribute was voted into the
-working draft. If the attribute is not supported by the current compliation
-target, this macro evaluates to 0. It can be used like this:
+This function-like macro is available in C++2a by default, and is provided as
an
+extension in earlier language standards. It takes a single argument that is the
+name of a double-square-bracket-style attribute. The argument can either be a
+single identifier or a scoped identifier. If the attribute is supported, a
+nonzero value is returned. If the attribute is a standards-based attribute,
this
+macro returns a nonzero value based on the year and month in which the
attribute
+was voted into the working draft. See `WG21 SD-6
+<https://isocpp.org/std/standing-documents/sd-6-sg10-feature-test-recommendations>`_
+for the list of values returned for standards-based attributes. If the
attribute
+is not supported by the current compliation target, this macro evaluates to 0.
+It can be used like this:
.. code-block:: c++
- #ifndef __has_cpp_attribute // Optional of course.
- #define __has_cpp_attribute(x) 0 // Compatibility with non-clang
compilers.
+ #ifndef __has_cpp_attribute // For backwards compatibility
+ #define __has_cpp_attribute(x) 0
#endif
...
@@ -134,10 +138,11 @@ target, this macro evaluates to 0. It c
#endif
...
-The attribute identifier (but not scope) can also be specified with a preceding
-and following ``__`` (double underscore) to avoid interference from a macro
with
-the same name. For instance, ``gnu::__const__`` can be used instead of
-``gnu::const``.
+The attribute scope tokens ``clang`` and ``_Clang`` are interchangeable, as are
+the attribute scope tokens ``gnu`` and ``__gnu__``. Attribute tokens in either
+of these namespaces can be specified with a preceding and following ``__``
+(double underscore) to avoid interference from a macro with the same name. For
+instance, ``gnu::__const__`` can be used instead of ``gnu::const``.
``__has_c_attribute``
---------------------
@@ -162,11 +167,11 @@ current compilation target, this macro e
#endif
...
-The attribute identifier (but not scope) can also be specified with a preceding
-and following ``__`` (double underscore) to avoid interference from a macro
with
-the same name. For instance, ``gnu::__const__`` can be used instead of
-``gnu::const``.
-
+The attribute scope tokens ``clang`` and ``_Clang`` are interchangeable, as are
+the attribute scope tokens ``gnu`` and ``__gnu__``. Attribute tokens in either
+of these namespaces can be specified with a preceding and following ``__``
+(double underscore) to avoid interference from a macro with the same name. For
+instance, ``gnu::__const__`` can be used instead of ``gnu::const``.
``__has_attribute``
-------------------
_______________________________________________
cfe-commits mailing list
cfe-commits@lists.llvm.org
http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
