diff -durN gcc-4.4.5.orig/gcc/doc/invoke.texi gcc-4.4.5/gcc/doc/invoke.texi
--- gcc-4.4.5.orig/gcc/doc/invoke.texi	2010-10-09 22:59:03.000000000 +0200
+++ gcc-4.4.5/gcc/doc/invoke.texi	2010-10-09 22:59:33.000000000 +0200
@@ -5432,6 +5432,11 @@
 Please note the warning under @option{-fgcse} about
 invoking @option{-O2} on programs that use computed gotos.
 
+NOTE: In Gentoo, @option{-D_FORTIFY_SOURCE=2} is set by default, and is
+activated when @option{-O} is set to 2 or higher.  This enables additional
+compile-time and run-time checks for several libc functions.  To disable,
+specify either @option{-U_FORTIFY_SOURCE} or @option{-D_FORTIFY_SOURCE=0}.
+
 @item -O3
 @opindex O3
 Optimize yet more.  @option{-O3} turns on all optimizations specified
diff -durN gcc-4.4.5.orig/gcc/gcc.c gcc-4.4.5/gcc/gcc.c
--- gcc-4.4.5.orig/gcc/gcc.c	2010-01-09 01:05:06.000000000 +0100
+++ gcc-4.4.5/gcc/gcc.c	2010-10-09 22:59:33.000000000 +0200
@@ -807,6 +807,7 @@
  %{H} %C %{D*&U*&A*} %{i*} %Z %i\
  %{fmudflap:-D_MUDFLAP -include mf-runtime.h}\
  %{fmudflapth:-D_MUDFLAP -D_MUDFLAPTH -include mf-runtime.h}\
+ %{!D_FORTIFY_SOURCE:%{!D_FORTIFY_SOURCE=*:%{!U_FORTIFY_SOURCE:-D_FORTIFY_SOURCE=2}}}\
  %{E|M|MM:%W{o*}}";
 
 /* This contains cpp options which are common with cc1_options and are passed