From: Mike Frysinger <vapier@gentoo.org>
Date: Sat, 20 Jan 2007 13:43:39 +0000 (-0000)
Subject: forgot to document strict alias warnings
X-Git-Tag: v2.1.2-r3~14
X-Git-Url: http://git.tremily.us/?a=commitdiff_plain;h=c810ebde215ff5698cbbdd35021c61c704b150e5;p=portage.git

forgot to document strict alias warnings

svn path=/main/trunk/; revision=5733
---

diff --git a/doc/qa.docbook b/doc/qa.docbook
index d4c920867..22cefa8d2 100644
--- a/doc/qa.docbook
+++ b/doc/qa.docbook
@@ -214,6 +214,20 @@
    </programlisting>
   </para>
   <para>
+   This warning crops up when code starts casting distinct pointer types and
+   then dereferencing them.  Generally, this is a violation of aliasing rules
+   which are part of the C standard.  Historically, these warnings did not show
+   up as the optimization was not turned on by default.  With gcc-4.1.x and
+   newer though, the -O2 optimization level enables strict aliasing support.
+   For information, please review these links:
+   <ulink url="http://mail-index.netbsd.org/tech-kern/2003/08/11/0001.html">NetBSD Explanation</ulink>,
+   <ulink url="http://thread.gmane.org/gmane.linux.gentoo.devel/39495">Gentoo Dev Thread</ulink>,
+   <ulink url="http://gcc.gnu.org/bugs.html#nonbugs_c">GCC Docs</ulink>
+  </para>
+  <para>
+   To fix this issue, use the methods proposed in the links mentioned earlier.
+   If you're unable to do so, then a work around would be to append the gcc
+   -fno-strict-aliasing flag to CFLAGS in the ebuild.
   </para>
  </sect1>