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| -rw-r--r-- | www/compatibility.html | 46 |
1 files changed, 24 insertions, 22 deletions
diff --git a/www/compatibility.html b/www/compatibility.html index ca1553150b..aa6a39dda1 100644 --- a/www/compatibility.html +++ b/www/compatibility.html @@ -65,7 +65,7 @@ <li><a href="#implicit-downcasts">Implicit downcasts</a></li> </ul> <ul> - <li><a href="#Use of class as method name">Use of class as method name</a></li> + <li><a href="#class-as-property-name">Using <code>class</code> as a property name</a></li> </ul> </li> </ul> @@ -418,8 +418,8 @@ compatibility with GNU C and C99 programs:</p> <ul> <li>The element type of a variable length array must be a POD ("plain old data") type, which means that it cannot have any - user-declared constructors or destructors, base classes, or any - members if non-POD type. All C types are POD types.</li> + user-declared constructors or destructors, any base classes, or any + members of non-POD type. All C types are POD types.</li> <li>Variable length arrays cannot be used as the type of a non-type template parameter.</li> </ul> @@ -428,12 +428,9 @@ template parameter.</li> </ul> <ol> <li>replace the variable length array with a fixed-size array if you can - determine a - reasonable upper bound at compile time; sometimes this is as + determine a reasonable upper bound at compile time; sometimes this is as simple as changing <tt>int size = ...;</tt> to <tt>const int size - = ...;</tt> (if the definition of <tt>size</tt> is a compile-time - integral constant);</li> -<li>use <tt>std::string</tt> instead of a <tt>char []</tt>;</li> + = ...;</tt> (if the initializer is a compile-time constant);</li> <li>use <tt>std::vector</tt> or some other suitable container type; or</li> <li>allocate the array on the heap instead using <tt>new Type[]</tt> - @@ -762,18 +759,18 @@ void f(int a, int a); <!-- ======================================================================= --> <p>Due to a bug in its implementation, GCC allows implicit downcasts -(from base class to a derived class) when calling functions. Such code is -inherently unsafe, since the object might not actually be an instance -of the derived class, and is rejected by Clang. For example, given -this code:</p> +of Objective-C pointers (from a base class to a derived class) when +calling functions. Such code is inherently unsafe, since the object +might not actually be an instance of the derived class, and is +rejected by Clang. For example, given this code:</p> <pre> @interface Base @end @interface Derived : Base @end -void f(Derived *); -void g(Base *base) { - f(base); +void f(Derived *p); +void g(Base *p) { + f(p); } </pre> @@ -781,11 +778,11 @@ void g(Base *base) { <pre> downcast.mm:6:3: error: no matching function for call to 'f' - f(base); + f(p); ^ downcast.mm:4:6: note: candidate function not viable: cannot convert from superclass 'Base *' to subclass 'Derived *' for 1st argument -void f(Derived *); +void f(Derived *p); ^ </pre> @@ -798,13 +795,17 @@ explicit cast:</p> </pre> <!-- ======================================================================= --> -<h3 id="Use of class as method name">Use of class as method name</h3> +<h3 id="class-as-property-name">Using <code>class</code> as a property name</h3> <!-- ======================================================================= --> -<p>Use of 'class' name to declare a method is allowed in objective-c++ mode to -be compatible with GCC. However, use of property dot syntax notation to call -this method is not allowed in clang++, as [I class] is a suitable syntax that -will work. So, this test will fail in clang++. +<p>In C and Objective-C, <code>class</code> is a normal identifier and +can be used to name fields, ivars, methods, and so on. In +C++, <code>class</code> is a keyword. For compatibility with existing +code, Clang permits <code>class</code> to be used as part of a method +selector in Objective-C++, but this does not extend to any other part +of the language. In particular, it is impossible to use property dot +syntax in Objective-C++ with the property name <code>class</code>, so +the following code will fail to parse:</p> <pre> @interface I { @@ -818,6 +819,7 @@ int cls; @end <pre> +<p>Use explicit message-send syntax instead, i.e. <code>[I class]</code>.</p> </div> </body> |