[wwwdocs] Add a note about in-class initialization of static data member

Marek Polacek polacek@redhat.com
Thu Feb 11 16:40:00 GMT 2016


On Thu, Feb 11, 2016 at 03:26:13PM +0000, Jonathan Wakely wrote:
> On 11/02/16 15:20 +0100, Marek Polacek wrote:
> >Does this look ok?
> 
> Looks OK, although how about stressing that it was only allowed as an
> extension previously, e.g. ...

So like this?  I've also added a note about stricter flexarr members rules.

Index: porting_to.html
===================================================================
RCS file: /cvs/gcc/wwwdocs/htdocs/gcc-6/porting_to.html,v
retrieving revision 1.9
diff -u -r1.9 porting_to.html
--- porting_to.html	10 Feb 2016 17:21:54 -0000	1.9
+++ porting_to.html	11 Feb 2016 16:38:38 -0000
@@ -269,6 +269,41 @@
 to port the code to use C++11's <code>std::unique_ptr</code> instead.
 </p>
 
+<h3>'constexpr' needed for in-class initialization of static data member</h3>
+
+<p>
+Since C++11, the <code>constexpr</code> keyword is needed when initializing
+a non-integral static data member in a class.  Thus the following program is
+accepted in C++03 (albeit with a <tt>-Wpedantic</tt> warning):
+</p>
+
+<pre><code>
+struct X {
+  const static double i = 10;
+};
+</pre></code>
+
+<p>
+The C++11 standard supports that in-class initialization using
+<code>constexpr</code> instead, so the GNU extension is no longer supported for
+C++11 or later.  Programs relying on the extension will be rejected with an
+error.  The fix is to use <code>constexpr</code> instead of <code>const</code>.
+</p>
+
+<h3>Stricter flexible array member rules</h3>
+
+<p>
+As of this release, the C++ compiler is now more strict about flexible array
+member rules.  As a consequence, the following code is no longer accepted:
+</p>
+
+<pre><code>
+union U {
+  int i;
+  char a[];
+};
+</pre></code>
+
 <h2>-Wmisleading-indentation</h2>
 <p>
 A new warning <code>-Wmisleading-indentation</code> was added

	Marek



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