Fix regression in OS VM files

The 2.5.7 source code archive contained outdated VM files of Memory.vm and Sys.vm. The official software suite 2.6 zip archive already contained an updated version of the OS VM files. The source code archive on the nand2tetris website was however never updated accordingly.

The OS update addressed the following issues:
1. Sys.error included a call to String.new which could cause itself a runtime error via Memory.alloc, resulting in recursive calls to Sys.error and ultimately crashing with a stack overflow.
2. Memory.vm contains now a better allocation algorithm with defragmentation of adjacent blocks

Author: Axel Kern

n2t-software-suite/OS/Memory.vm

@@ -37,9 +37,9 @@ push temp 0
 pop that 0
 push constant 0
 return
-function Memory.alloc 1
+function Memory.alloc 2
 push argument 0
-push constant 1
+push constant 0
 lt
 if-goto IF_TRUE0
 goto IF_FALSE0
@@ -48,38 +48,135 @@ push constant 5
 call Sys.error 1
 pop temp 0
 label IF_FALSE0
+push argument 0
+push constant 0
+eq
+if-goto IF_TRUE1
+goto IF_FALSE1
+label IF_TRUE1
+push constant 1
+pop argument 0
+label IF_FALSE1
 push constant 2048
 pop local 0
 label WHILE_EXP0
+push local 0
+push constant 16383
+lt
 push constant 0
 push local 0
 add
 pop pointer 1
 push that 0
 push argument 0
 lt
+and
 not
 if-goto WHILE_END0
 push constant 1
 push local 0
 add
 pop pointer 1
 push that 0
+pop local 1
+push constant 0
+push local 0
+add
+pop pointer 1
+push that 0
+push constant 0
+eq
+push local 1
+push constant 16382
+gt
+or
+push constant 0
+push local 1
+add
+pop pointer 1
+push that 0
+push constant 0
+eq
+or
+if-goto IF_TRUE2
+goto IF_FALSE2
+label IF_TRUE2
+push local 1
 pop local 0
+goto IF_END2
+label IF_FALSE2
+push constant 0
+push local 0
+add
+push constant 1
+push local 0
+add
+pop pointer 1
+push that 0
+push local 0
+sub
+push constant 0
+push local 1
+add
+pop pointer 1
+push that 0
+add
+pop temp 0
+pop pointer 1
+push temp 0
+pop that 0
+push constant 1
+push local 1
+add
+pop pointer 1
+push that 0
+push local 1
+push constant 2
+add
+eq
+if-goto IF_TRUE3
+goto IF_FALSE3
+label IF_TRUE3
+push constant 1
+push local 0
+add
+push local 0
+push constant 2
+add
+pop temp 0
+pop pointer 1
+push temp 0
+pop that 0
+goto IF_END3
+label IF_FALSE3
+push constant 1
+push local 0
+add
+push constant 1
+push local 1
+add
+pop pointer 1
+push that 0
+pop temp 0
+pop pointer 1
+push temp 0
+pop that 0
+label IF_END3
+label IF_END2
 goto WHILE_EXP0
 label WHILE_END0
 push local 0
 push argument 0
 add
 push constant 16379
 gt
-if-goto IF_TRUE1
-goto IF_FALSE1
-label IF_TRUE1
+if-goto IF_TRUE4
+goto IF_FALSE4
+label IF_TRUE4
 push constant 6
 call Sys.error 1
 pop temp 0
-label IF_FALSE1
+label IF_FALSE4
 push constant 0
 push local 0
 add
@@ -89,9 +186,9 @@ push argument 0
 push constant 2
 add
 gt
-if-goto IF_TRUE2
-goto IF_FALSE2
-label IF_TRUE2
+if-goto IF_TRUE5
+goto IF_FALSE5
+label IF_TRUE5
 push argument 0
 push constant 2
 add
@@ -119,9 +216,9 @@ push local 0
 push constant 2
 add
 eq
-if-goto IF_TRUE3
-goto IF_FALSE3
-label IF_TRUE3
+if-goto IF_TRUE6
+goto IF_FALSE6
+label IF_TRUE6
 push argument 0
 push constant 3
 add
@@ -136,8 +233,8 @@ pop temp 0
 pop pointer 1
 push temp 0
 pop that 0
-goto IF_END3
-label IF_FALSE3
+goto IF_END6
+label IF_FALSE6
 push argument 0
 push constant 3
 add
@@ -152,7 +249,7 @@ pop temp 0
 pop pointer 1
 push temp 0
 pop that 0
-label IF_END3
+label IF_END6
 push constant 1
 push local 0
 add
@@ -165,7 +262,7 @@ pop temp 0
 pop pointer 1
 push temp 0
 pop that 0
-label IF_FALSE2
+label IF_FALSE5
 push constant 0
 push local 0
 add

n2t-software-suite/OS/Sys.vm

@@ -65,15 +65,14 @@ label WHILE_END0
 push constant 0
 return
 function Sys.error 0
-push constant 3
-call String.new 1
 push constant 69
-call String.appendChar 2
+call Output.printChar 1
+pop temp 0
 push constant 82
-call String.appendChar 2
+call Output.printChar 1
+pop temp 0
 push constant 82
-call String.appendChar 2
-call Output.printString 1
+call Output.printChar 1
 pop temp 0
 push argument 0
 call Output.printInt 1