review comments

Author: awortman-fastly

lucet-module/src/version_info.rs

@@ -13,6 +13,14 @@ pub struct VersionInfo {
     minor: u16,
     patch: u16,
     reserved: u16,
+    /// `version_hash` is either all nulls or the first eight ascii characters of the git commit
+    /// hash of wherever this Version is coming from. In the case of a compiled lucet module, this
+    /// hash will come from the git commit that the lucetc producing it came from. In a runtime
+    /// context, it will be the git commit of lucet-runtime built into the embedder.
+    ///
+    /// The version hash will typically populated only in release builds, but may blank even in
+    /// that case: if building from a packagd crate, or in a build environment that does not have
+    /// "git" installed, `lucetc` and `lucet-runtime` will fall back to an empty hash.
     version_hash: [u8; 8],
 }
 

lucetc/src/output.rs

@@ -1,7 +1,6 @@
 use crate::error::LucetcErrorKind;
 use crate::function_manifest::{write_function_manifest, FUNCTION_MANIFEST_SYM};
 use crate::name::Name;
-use crate::pointer::NATIVE_POINTER_SIZE;
 use crate::stack_probe;
 use crate::table::{link_tables, TABLE_SYM};
 use crate::traps::write_trap_tables;
@@ -10,7 +9,9 @@ use cranelift_codegen::{ir, isa};
 use cranelift_faerie::FaerieProduct;
 use faerie::{Artifact, Decl, Link};
 use failure::{format_err, Error, ResultExt};
-use lucet_module::{FunctionSpec, VersionInfo, LUCET_MODULE_SYM, MODULE_DATA_SYM};
+use lucet_module::{
+    FunctionSpec, SerializedModule, VersionInfo, LUCET_MODULE_SYM, MODULE_DATA_SYM,
+};
 use std::collections::HashMap;
 use std::fs::File;
 use std::io::{Cursor, Write};
@@ -136,7 +137,7 @@ fn write_module(
     function_manifest_len: usize,
     obj: &mut Artifact,
 ) -> Result<(), Error> {
-    let mut native_data = Cursor::new(Vec::with_capacity(16 + NATIVE_POINTER_SIZE * 4));
+    let mut native_data = Cursor::new(Vec::with_capacity(std::mem::size_of::<SerializedModule>()));
     obj.declare(LUCET_MODULE_SYM, Decl::data().global())
         .context(format!("declaring {}", LUCET_MODULE_SYM))?;