4915

In the process of building next-token I finally added some support for a
debugging situation I've found myself in a couple of times: wondering "what
changed this memory location"?

1 files changed, 6 insertions, 0 deletions

diff --git a/subx/Readme.md b/subx/Readme.md
index 42f2cedb..93ef21e1 100644
--- a/subx/Readme.md
+++ b/subx/Readme.md
@@ -466,6 +466,12 @@ rudimentary but hopefully still workable toolkit:
   Now the trace should have a lot more detail on which of these labels was
   reached, and precisely when the exit was taken.
 
+* If you find yourself wondering, "when did the contents of this memory
+  address change?", `subx run` has some rudimentary support for _watch
+  points_. Just insert a label starting with `$watch-` before an instruction
+  that writes to the address, and its value will start getting dumped to the
+  trace after every instruction thereafter.
+
 * Once we have a sense for precisely which instructions we want to look at,
   it's time to look at the trace as a whole. Key is the state of registers
   before each instruction. If a function is receiving bad arguments it becomes