From 54709e55f8460c83fc0225cb78ada3331a2f125c Mon Sep 17 00:00:00 2001
From: Dane Johnson <daneallenjohnson@protonmail.com>
Date: Mon, 25 Aug 2025 17:26:11 -0500
Subject: [PATCH] Added stepping to debugger

---
 scmvm.scm          |  2 +-
 scmvm/debugger.scm | 21 ++++++++++++++-------
 tests.scm          | 17 ++++++++++++++++-
 3 files changed, 31 insertions(+), 9 deletions(-)

diff --git a/scmvm.scm b/scmvm.scm
index 8b47b2d..71630e0 100644
--- a/scmvm.scm
+++ b/scmvm.scm
@@ -10,7 +10,7 @@
                ;; assembler
                assemble
                ;; debugger
-               make-debugger debugger-continue
+               make-debugger debugger-continue debugger-step
                debugger-vm
                debugger-breakpoints debugger-breakpoints-set!
                debugger-breakpoint-add! debugger-breakpoint-ref
diff --git a/scmvm/debugger.scm b/scmvm/debugger.scm
index 8cdaa87..56141c8 100644
--- a/scmvm/debugger.scm
+++ b/scmvm/debugger.scm
@@ -12,15 +12,16 @@
             debugger-breakpoint-add! debugger-breakpoint-ref
             debugger-breakpoint-enable! debugger-breakpoint-disable!
             debugger-breakpoint-delete!
-            debugger-continue))
+            debugger-step debugger-continue))
 
 (define-record-type <debugger>
-  (make-debugger vm source breakpoints continuation)
+  (make-debugger vm source breakpoints continuation stepping)
   debugger?
   (vm debugger-vm)
   (source debugger-source)
   (breakpoints debugger-breakpoints)
-  (continuation debugger-continuation debugger-continuation-set!))
+  (continuation debugger-continuation debugger-continuation-set!)
+  (stepping debugger-stepping? debugger-stepping-set!))
 
 (define (make-breakpoints labels)
   (define the-breakpoints '())
@@ -51,17 +52,23 @@
   (define the-debugger #f)
   (define (debug)
     (shift k
-      (if (((debugger-breakpoints the-debugger) 'ref) (vm-pc (debugger-vm the-debugger)))
-          (debugger-continuation-set! the-debugger k)
-          (k))))
+     (if (or (debugger-stepping? the-debugger)
+             (((debugger-breakpoints the-debugger) 'ref) (vm-pc (debugger-vm the-debugger))))
+         (debugger-continuation-set! the-debugger k)
+         (k))))
   (define vm (make-vm #:debugger debug))
   (vm-load-program! vm prgm)
-  (set! the-debugger (make-debugger vm source (make-breakpoints symbols) #f))
+  (set! the-debugger (make-debugger vm source (make-breakpoints symbols) #f #f))
   (debugger-breakpoint-add! the-debugger 1)
   (reset (run-vm vm))
   the-debugger)
 
 (define (debugger-continue debugger)
+  (debugger-stepping-set! debugger #f)
+  ((debugger-continuation debugger)))
+
+(define (debugger-step debugger)
+  (debugger-stepping-set! debugger #t)
   ((debugger-continuation debugger)))
 
 (define (debugger-breakpoint-add! debugger breakpoint)
diff --git a/tests.scm b/tests.scm
index b69571a..34844f6 100644
--- a/tests.scm
+++ b/tests.scm
@@ -144,4 +144,19 @@
     (stack-pop my-data)
     (stack-push my-data 1)
     (debugger-continue my-debugger)
-    (assert-equal 1 (vm-memory-ref my-vm 1))))
+    (assert-equal 1 (vm-memory-ref my-vm 1)))
+  (define-test "stepping"
+    (define my-debugger (make-debugger fib-program-asm))
+    (define my-vm (debugger-vm my-debugger))
+    (vm-memory-set! my-vm 1 10)
+    (vm-pc-set! my-vm 5)
+    (debugger-breakpoint-add! my-debugger 'fib)
+    (debugger-continue my-debugger)
+    (assert-equal 23 (vm-pc my-vm))
+    (debugger-step my-debugger)
+    (assert-equal 24 (vm-pc my-vm)) ;; dup is a 1 byte instruction
+    (debugger-step my-debugger)
+    (assert-equal 29 (vm-pc my-vm)) ;; push is a 5 byte instruction
+    (debugger-continue my-debugger)
+    (assert-equal 23 (vm-pc my-vm)) ;; continue stops stepping
+    ))