From ac0e27197fa304b928c2e9d331b467c5fe5176f9 Mon Sep 17 00:00:00 2001
From: Adam Eury <euryadam@gmail.com>
Date: Sun, 21 Jan 2024 00:05:10 -0500
Subject: [PATCH] Terminate variables with string literals with a zero.

---
 examples/print.g | 12 +++++++-----
 gmachine.go      |  2 +-
 gmachine_test.go | 12 +++++++++---
 3 files changed, 17 insertions(+), 9 deletions(-)

diff --git a/examples/print.g b/examples/print.g
index 89a2345..6484d18 100644
--- a/examples/print.g
+++ b/examples/print.g
@@ -1,12 +1,14 @@
+JUMP run
 VARB msg "hello world"
 
 .run
-SETX msg 	; set X register to the address of msg
+SETX msg 	    ; set X register to the address of msg
+JUMP print
 
 .print
-MOVE *X -> A		; move the value of address in X to A
-OUTA		; print A
-INCX		; increment address stored in X
-JANZ print	; jump to label 'done' if A = 0
+MOVE *X -> A    ; move the value at address in X to A
+OUTA		    ; print A
+INCX		    ; increment address stored in X
+JANZ print	    ; jump to label 'done' if A = 0
 HALT
 
diff --git a/gmachine.go b/gmachine.go
index abcfca9..fd3978f 100644
--- a/gmachine.go
+++ b/gmachine.go
@@ -293,7 +293,7 @@ func Assemble(reader io.Reader) ([]Word, error) {
 			case ast.IntegerLiteral:
 				program = append(program, Word(operand.Value))
 			case ast.StringLiteral:
-				strSlice := make([]Word, len(operand.Value))
+				strSlice := make([]Word, len(operand.Value)+1)
 				for i, c := range operand.Value {
 					strSlice[i] = Word(c)
 				}
diff --git a/gmachine_test.go b/gmachine_test.go
index f231c70..8b53c3d 100644
--- a/gmachine_test.go
+++ b/gmachine_test.go
@@ -914,12 +914,18 @@ HALT
 func TestVARB_DeclaresAStringVariableInMemory(t *testing.T) {
 	t.Parallel()
 	g := gmachine.New(nil)
-	err := assembleAndRunFromString(g, `VARB msg "hello world"`)
+	err := assembleAndRunFromString(g, `
+JUMP start
+VARB msg "hello world"
+.start
+HALT
+`)
 	if err != nil {
 		t.Fatal("didn't expect an error:", err)
 	}
-	want := []gmachine.Word{'h', 'e', 'l', 'l', 'o', ' ', 'w', 'o', 'r', 'l', 'd'}
-	got := g.Memory[int(g.MemOffset) : int(g.MemOffset)+len(want)]
+	want := []gmachine.Word{'h', 'e', 'l', 'l', 'o', ' ', 'w', 'o', 'r', 'l', 'd', 0}
+	offsetStart := int(g.MemOffset) + 2
+	got := g.Memory[offsetStart : offsetStart+len(want)]
 	if !cmp.Equal(want, got) {
 		t.Error(cmp.Diff(want, got))
 	}