diff -urpN src/gdb/doc/gdb.texinfo dev/gdb/doc/gdb.texinfo
--- src/gdb/doc/gdb.texinfo	2008-04-21 06:23:26.000000000 +0200
+++ dev/gdb/doc/gdb.texinfo	2008-04-22 07:10:59.000000000 +0200
@@ -9903,6 +9903,12 @@ of the second one.
 @item :
 The range operator.  Normally used in the form of array(low:high) to
 represent a section of array.
+
+@item %
+The access component operator.  Normally used to access elements in derived
+types.  Also suitable for unions.  As unions aren't part of regular fortran
+this can only happen when accessing a register that uses a gdbarch-defined
+union type.
 @end table
 
 @node Fortran Defaults