update docs regarding --debug

* doc/ref/scheme-scripts.texi (Invoking Guile): Update docs on --debug.

diff --git a/doc/ref/scheme-scripts.texi b/doc/ref/scheme-scripts.texi
index fcb22a6..8d47746 100644 (file)
--- a/doc/ref/scheme-scripts.texi
+++ b/doc/ref/scheme-scripts.texi
@@ -174,15 +174,19 @@ guile --use-srfi=8,13
 @end example
 
 @item --debug
-Start with the debugging evaluator and enable backtraces.  Using the
-debugging evaluator will give you better error messages but it will
-slow down execution.  By default, the debugging evaluator is only used
-when entering an interactive session.  When executing a script with
-@code{-s} or @code{-c}, the normal, faster evaluator is used by default.
+Start with the debugging virtual machine engine.  Using the debugging VM
+will enable support for VM hooks, which are needed for tracing,
+breakpoints, and accurate call counts when profiling.  The debugging VM
+is slower than the regular VM, though, by about 10 percent.  @xref{VM
+Hooks}, for more information.
+
+By default, the debugging VM engine is only used when entering an
+interactive session.  When executing a script with @code{-s} or
+@code{-c}, the normal, faster VM is used by default.
 
 @vnew{1.8}
 @item --no-debug
-Do not use the debugging evaluator, even when entering an interactive
+Do not use the debugging VM engine, even when entering an interactive
 session.
 
 @item -h@r{, }--help