update debugging information in readme file

diff --git a/doc/README.txt b/doc/README.txt
index 268b9afabd664fb6dda2be85fb8863941c850c72..ddb8763c9ec22c975bd0ad15a1d695455cbd2c50 100644 (file)
--- a/doc/README.txt
+++ b/doc/README.txt
@@ -27,3 +27,18 @@ Run the model checker.
 
 Use dot (from graphviz) to convert the outputted dot files into the
 format of your choice.
 
 Use dot (from graphviz) to convert the outputted dot files into the
 format of your choice.

+
+III. Using the debugger (gdb).
+
+You can launch the debugger by passing in the gdb option to run.sh (or
+you can lok at run.sh to see how to launch the model checker from
+within a debugger).  Since we trap SIGSEGV to detect pages that we
+need to update, you have to disable stopping on SIGSEGV.  To do this,
+use the following commands:
+
+To run inside MacOS under gdb you need (lldb won't work as far as I know):
+set dont-handle-bad-access 1 (sometime not necessary)
+handle SIGBUS nostop noprint
+
+To run in Linux under gdb, use:
+handle SIGSEGV nostop noprint