Mention that GCC reorders statements.

diff --git a/doc/debug.texi b/doc/debug.texi
index 82f001ffbe91ffbdb2dedc912c4c08f202ba6059..19270f46e46c19aa4d8897195a68622af032b913 100644 (file)
--- a/doc/debug.texi
+++ b/doc/debug.texi
@@ -201,7 +201,15 @@ address.
 (Use a @samp{0x} prefix to specify an address in hex.)
 @end table
 
-If you notice unexplainable behavior while using @command{gdb}, there
+You might notice that @command{gdb} tends to show code being executed
+in an order different from the order in the source.  That is, the
+current statement jumps around seemingly randomly.  This is due to
+GCC's optimizer, which does tend to reorder code.  If it bothers you,
+you can turn off optimization by editing
+@file{pintos/src/Make.config}, removing @option{-O3} from the
+@code{CFLAGS} definition.
+
+If you notice other strange behavior while using @command{gdb}, there
 are three possibilities.  The first is that there is a bug in your
 modified Pintos.  The second is that there is a bug in Bochs's
 interface to @command{gdb} or in @command{gdb} itself.  The third is