wasm: Create a global for __stack_pointer

compiler/gen_wasm/src/backend.rs

@@ -86,6 +86,14 @@ impl<'a> WasmBackend<'a> {
             }
         }
 
+        module.global.append(Global {
+            ty: GlobalType {
+                value_type: ValueType::I32,
+                is_mutable: true,
+            },
+            init: ConstExpr::I32(1234), // TODO: come up with a value!
+        });
+
         module.export.exports = app_exports;
         module.code.code_builders.reserve(proc_lookup.len());
 

compiler/gen_wasm/src/wasm_module/mod.rs

@@ -105,6 +105,7 @@ impl<'a> WasmModule<'a> {
         let function = FunctionSection::parse(arena, bytes, &mut cursor)?;
         let table = TableSection::parse((), bytes, &mut cursor)?;
         let memory = MemorySection::parse(arena, bytes, &mut cursor)?;
+        let global_start = cursor;
         let global = GlobalSection::parse(arena, bytes, &mut cursor)?;
         let export = ExportSection::parse(arena, bytes, &mut cursor)?;
         let start = OpaqueSection::parse((arena, SectionId::Start), bytes, &mut cursor)?;
@@ -127,6 +128,13 @@ impl<'a> WasmModule<'a> {
         let reloc_data = RelocationSection::parse((arena, "reloc.DATA"), bytes, &mut cursor)?;
         let names = NameSection::parse(arena, bytes, &mut cursor)?;
 
+        if global.count != 0 {
+            return Err(ParseError {
+                offset: global_start,
+                message: format!("All globals in a relocatable Wasm module should be imported, but found {} internally defined", global.count),
+            });
+        }
+
         Ok(WasmModule {
             types,
             import,

compiler/gen_wasm/src/wasm_module/sections.rs

@@ -385,14 +385,15 @@ impl<'a> ImportSection<'a> {
 
 impl<'a> Parse<&'a Bump> for ImportSection<'a> {
     fn parse(arena: &'a Bump, module_bytes: &[u8], cursor: &mut usize) -> Result<Self, ParseError> {
+        let start = *cursor;
         let (count, range) = parse_section(Self::ID, module_bytes, cursor)?;
         let mut bytes = Vec::with_capacity_in(range.len() * 2, arena);
         let mut fn_signatures = Vec::with_capacity_in(range.len() / 8, arena);
 
         let end = range.end;
-        bytes.extend_from_slice(&module_bytes[range]);
 
         while *cursor < end {
+            let import_start = *cursor;
             String::skip_bytes(module_bytes, cursor)?; // import namespace
             String::skip_bytes(module_bytes, cursor)?; // import name
 
@@ -403,6 +404,7 @@ impl<'a> Parse<&'a Bump> for ImportSection<'a> {
                 ImportTypeId::Func => {
                     let sig = u32::parse((), module_bytes, cursor)?;
                     fn_signatures.push(sig);
+                    bytes.extend_from_slice(&module_bytes[import_start..*cursor]);
                 }
                 ImportTypeId::Table => {
                     TableType::skip_bytes(module_bytes, cursor)?;
@@ -416,6 +418,8 @@ impl<'a> Parse<&'a Bump> for ImportSection<'a> {
             }
         }
 
+        dbg!(bytes.len(), end - start);
+
         Ok(ImportSection {
             count,
             fn_signatures,