Recommend compiling with PIC consistently.

While shared objects with non-PIC code work on some architectures
(notably x86), unless code is always PIC on that arch (not true for x86)
doing so requires runtime relocations, which prevents the object
actually being shared, and means such segments can't be marked as
read-only.

Doc/Manual/Ruby.html

@@ -259,14 +259,22 @@ operating system would look something like this: </p>
 
 <div class="code shell">
 <pre>$ swig -ruby example.i
-$ gcc -c example.c
-$ gcc -c example_wrap.c -I/usr/local/lib/ruby/1.6/i686-linux
+$ gcc -O2 -fPIC -c example.c
+$ gcc -O2 -fPIC -c example_wrap.c -I/usr/local/lib/ruby/1.6/i686-linux
 $ gcc -shared example.o example_wrap.o -o example.so
 </pre>
 </div>
 
-<p> For other platforms it may be necessary to compile with the <tt>-fPIC</tt>
-option to generate position-independent code. If in doubt, consult the
+<p>
+The -fPIC option tells GCC to generate position-independent code (PIC)
+which is required for most architectures (it's not vital on x86, but
+still a good idea as it allows code pages from the library to be shared between
+processes).  Other compilers may need a different option specified instead of
+-fPIC.
+</p>
+
+<p>
+If in doubt, consult the
 manual pages for your compiler and linker to determine the correct set
 of options. You might also check the <a href="http://www.dabeaz.com/cgi-bin/wiki.pl">SWIG Wiki</a>
 for additional information. </p>
@@ -325,8 +333,8 @@ using the C++ compiler. For example: </p>
 <div class="code shell">
 <pre>
 $ swig -c++ -ruby example.i
-$ g++ -c example.cxx
-$ g++ -c example_wrap.cxx -I/usr/local/lib/ruby/1.6/i686-linux
+$ g++ -fPIC -c example.cxx
+$ g++ -fPIC -c example_wrap.cxx -I/usr/local/lib/ruby/1.6/i686-linux
 $ g++ -shared example.o example_wrap.o -o example.so
 </pre>
 </div>