Require assembler sections to specify where in virtual memory they begin

Signed-off-by: Alek Ratzloff <alekratz@gmail.com>

src/vm/obj/assemble/mod.rs

@@ -38,7 +38,6 @@ impl<'a> Assemble<'a> {
     }
 
     pub fn assemble(&mut self) -> Result<Object> {
-        let mut pos = 0;
         let mut sections = Vec::new();
 
         // gather global symbols
@@ -78,11 +77,9 @@ impl<'a> Assemble<'a> {
                         }
                     }
                     let (start, end) = match org {
-                        Some(SectionOrg::Start(start)) => (*start, start + bytes.len() as u64),
-                        Some(SectionOrg::Range(start, end)) => (*start, *end),
-                        None => (pos, pos + bytes.len() as u64),
+                        SectionOrg::Start(start) => (*start, start + bytes.len() as u64),
+                        SectionOrg::Range(start, end) => (*start, *end),
                     };
-                    pos = end;
 
                     let section = match block {
                         SectionBlock::Data { .. } => Section::Data {
@@ -121,10 +118,12 @@ impl<'a> Assemble<'a> {
 
     fn gather_symbols(block: &SectionBlock, export: bool) -> Result<HashMap<String, u64>> {
         match block {
-            SectionBlock::Data { body, .. } | SectionBlock::Code { body, .. } => {
+            SectionBlock::Data { org, body, .. } | SectionBlock::Code { org, body, .. } => {
                 let mut exports = HashSet::new();
                 let mut labels = HashMap::new();
-                let mut pos = 0;
+                let mut pos = match org {
+                    SectionOrg::Start(start) | SectionOrg::Range(start, _) => (*start) as usize,
+                };
                 for line in body.iter() {
                     match line {
                         Line::Inst(inst) => {

src/vm/obj/syn/ast.rs

@@ -3,11 +3,11 @@ use crate::vm::{inst::*, reg::Reg};
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub enum SectionBlock {
     Data {
-        org: Option<SectionOrg>,
+        org: SectionOrg,
         body: Vec<Line>,
     },
     Code {
-        org: Option<SectionOrg>,
+        org: SectionOrg,
         body: Vec<Line>,
     },
     Meta {

src/vm/obj/syn/parser.lalrpop

@@ -82,11 +82,11 @@ SectionOrg: SectionOrg = {
 }
 
 Section: SectionBlock = {
-    "data" <org:SectionOrg?> "{" <body:Line*> "}" => {
+    "data" <org:SectionOrg> "{" <body:Line*> "}" => {
         SectionBlock::Data { org, body }
     },
 
-    "code" <org:SectionOrg?> "{" <body:Line*> "}" => {
+    "code" <org:SectionOrg> "{" <body:Line*> "}" => {
         SectionBlock::Code { org, body }
     },