From 456bc951382741e34c4d17af01406ff7bda32f7b Mon Sep 17 00:00:00 2001
From: Luna <git@l4.pm>
Date: Sat, 1 Jun 2019 15:01:39 -0300
Subject: [PATCH] vm: add debug flags

---
 src/main.zig |  6 +-----
 src/vm.zig   | 22 ++++++++++++++++++++--
 2 files changed, 21 insertions(+), 7 deletions(-)

diff --git a/src/main.zig b/src/main.zig
index 1c982e3..1d4bdc7 100644
--- a/src/main.zig
+++ b/src/main.zig
@@ -118,11 +118,7 @@ pub fn main() !void {
 
     var constant = try chk.writeConstant(1.2, 123);
     try chk.write(chunk.OpCode.Return, 123);
-    try chk.disassemble(stdout, "test chunk");
 
-    var vmach = vm.VM.init(stdout, &chk);
-
-    std.debug.warn("vm start\n");
+    var vmach = vm.VM.init(stdout, &chk, true);
     _ = try vmach.interpret();
-    std.debug.warn("vm end\n");
 }
diff --git a/src/vm.zig b/src/vm.zig
index fd510b3..1765c6c 100644
--- a/src/vm.zig
+++ b/src/vm.zig
@@ -15,15 +15,23 @@ pub const VM = struct {
     chk: *Chunk,
     ip: usize,
     stdout: StdOut,
+    debug_flag: bool,
 
-    pub fn init(stdout: StdOut, chk: *Chunk) VM {
+    pub fn init(stdout: StdOut, chk: *Chunk, debug_flag: bool) VM {
         return VM{
             .stdout = stdout,
             .chk = chk,
             .ip = 0,
+            .debug_flag = debug_flag,
         };
     }
 
+    pub fn debug(self: *VM, comptime fmt: []const u8, args: ...) void {
+        if (self.debug_flag) {
+            std.debug.warn(fmt, args);
+        }
+    }
+
     fn readByte(self: *VM) u8 {
         var byte: u8 = self.chk.code[self.ip];
         self.ip += 1;
@@ -47,17 +55,23 @@ pub const VM = struct {
 
     fn run(self: *VM) !InterpretResult {
         while (true) {
+            if (self.debug_flag) {
+                _ = try self.chk.disassembleInstruction(self.stdout, self.ip);
+            }
+
             var instruction = self.readByte();
 
             switch (instruction) {
                 chunk.OpCode.Constant => blk: {
                     var constant = self.readConst();
                     try value.printValue(self.stdout, constant);
+                    try self.stdout.write("\n");
                     break :blk;
                 },
                 chunk.OpCode.ConstantLong => blk: {
                     var constant = self.readConstLong();
                     try value.printValue(self.stdout, constant);
+                    try self.stdout.write("\n");
                     break :blk;
                 },
                 chunk.OpCode.Return => blk: {
@@ -73,6 +87,10 @@ pub const VM = struct {
 
     pub fn interpret(self: *VM) !InterpretResult {
         self.ip = 0;
-        return try self.run();
+
+        self.debug("VM start\n");
+        var res = try self.run();
+        self.debug("VM end\n");
+        return res;
     }
 };