@@ -251,6 +251,99 @@
<b style='color:lime'>^</b>
</pre>
+<h4><code>__STDC_VERSION__</code> macro</h4>
+
+<p>In the C11 mode, the <code>__STDC_VERSION__</code> standard macro,
+introduced in C95, is now defined to <code>201112L</code>. Typically,
+this macro is used as in the following:</p>
+
+<pre><code>
+ #if !defined __STDC_VERSION__ || __STDC_VERSION__ < 199901L
+ /* ... */
+ #else
+ # include <stdint.h>
+ #endif
+</code></pre>
+
+<p>You can check the macro using <code>gcc -dM -E -std=gnu11 - < /dev/null | grep STDC_VER</code>.</p>
+
+<h4>Different meaning of the <code>%a *scanf</code> modifier</h4>
+
+<p>The GNU C library supports dynamic allocation via the <code>%a</code>
+modifier. But in C99, the <code>%a</code> modifier is a synonym for
+<code>%f</code> (float), so the compiler expects an argument of type
+<code>float *</code>. This in combination with the <code>-Wformat</code>
+warning option may result in additional warnings:</p>
+
+<pre><code>
+ #include <stdio.h>
+
+ int
+ main (void)
+ {
+ char *s;
+ scanf ("%as", &s);
+ }
+</code></pre>
+
+<pre>
+<b>q.c:7:10:</b> <b style='color:magenta'>warning:</b> format <b>'%a'</b> expects argument of type <b>'float *'</b>, but argument 2 has type <b>'char **'</b> [-Wformat=]
+ scanf ("%as", &s);
+ <b style='color:lime'>^</b>
+</pre>
+
+<p>The fix is to use the <code>%m</code> modifier instead, specified by
+POSIX.1-2008.</p>
+
+<h3>New warnings</h3>
+
+<p>Several new warnings have been added to the C front end. One of the new
+warnings is that GCC now warns about non-standard predefined macros with the
+<code>-Wpedantic</code> option. For instance:</p>
+
+<pre><code>
+ void
+ foo (void)
+ {
+ const char *s = __FUNCTION__;
+ }
+</code></pre>
+
+<pre>
+<b>q.c:4:19:</b> <b style='color:magenta'>warning:</b> ISO C does not support <b>'__FUNCTION__'</b> predefined identifier [-Wpedantic]
+ const char *s = __FUNCTION__;
+ <b style='color:lime'>^</b>
+</pre>
+
+<p>The fix is either to use the standard predefined macro <code>__func__</code>
+(since C99), or to use the <code>__extension__</code> keyword:<p/>
+
+<pre><code>
+ const char *s = __extension__ __FUNCTION__;
+</code></pre>
+
+<h2>C++ language issues</h2>
+
+<h3>Converting <code>std::nullptr_t</code> to <code>bool</code></h3>
+
+<p>Converting <code>std::nullptr_t</code> to <code>bool</code> in the C++11
+mode now requires direct-initialization. This has been changed in
+<a href="http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_defects.html#1423">DR 1423</a>.
+As a consequence, the following is invalid:</p>
+
+<pre><code>
+ bool b = nullptr;
+</code></pre>
+
+<p>but the following is valid:</p>
+
+<pre><code>
+ bool b(nullptr);
+</code></pre>
+
+It is recommended to use <code>true</code>, resp. <code>false</code> keywords
+in such cases.
+
<h3>Links</h3>
<p>