On 07/03/14 18:08 +0000, Jonathan Wakely wrote:
On 04/03/14 22:32 +0000, Jonathan Wakely wrote:
I've added an initial "Porting to GCC 4.9" page at
http://gcc.gnu.org/gcc-4.9/porting_to.html
So far it only contains a couple of C++ changes that caused some
failures during mass rebuilds, other additions are welcome.
The attached patch adds some more changes (thanks to Jakub for the
OpenMP one) and links to the porting guide form gcc-4.9/changes.html
This patch adds a note about a new warning (thanks to Marek), which
caused some build failures in binutils and gdb.
? .porting_to.html.swp
Index: porting_to.html
===================================================================
RCS file: /cvs/gcc/wwwdocs/htdocs/gcc-4.9/porting_to.html,v
retrieving revision 1.3
diff -u -r1.3 porting_to.html
--- porting_to.html 7 Mar 2014 19:19:51 -0000 1.3
+++ porting_to.html 7 Mar 2014 19:42:36 -0000
@@ -60,9 +60,32 @@
<code>#pragma omp end declare target</code> directive, this is now a parsing
error.</p>
-<!--
<h2>C language issues</h2>
--->
+
+<h3>Right operand of comma operator without effect</h3>
+
+<p>GCC now warns about unused right-hand side of a comma expression that
+contains no side effects:</p>
+
+<pre><code>
+ int i = 42;
+ bar (), i;
+</code></pre>
+
+<p>This example now gives the following diagnostic:</p>
+
+<pre>
+<b>w.c:5:9:</b> <b style='color:magenta'>warning:</b> right-hand operand of
comma expression has no effect [-Wunused-value]
+ bar (), i;
+ <b style='color:lime'>^</b>
+</pre>
+
+<p>To suppress this warning cast the right-hand operand to
<code>void</code>:</p>
+
+<pre><code>
+ int i = 42;
+ bar (), (void) i;
+</code></pre>
<h2>C++ language issues</h2>
