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Remove requirement that the module to link exports _start. #60

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Merged
peterhuene merged 2 commits into from
Aug 9, 2021
Merged

Remove requirement that the module to link exports _start. #60

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2c9d0c6
Remove requirement that the module to link exports `_start`.
peterhuene Aug 9, 2021
9970a1c
Also export memories from the linked module.
peterhuene Aug 9, 2021
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22 changes: 11 additions & 11 deletions crates/wasmlink-cli/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -41,13 +41,13 @@ pub struct App {
#[structopt(long, short = "p", value_name = "PROFILE")]
pub profile: String,

/// The path of the output linked module; defaults to replacing the main module.
/// The path of the output linked module; defaults to replacing the given module.
#[structopt(long, short = "o", value_name = "OUTPUT", parse(from_os_str))]
pub output: Option<PathBuf>,

/// The main module to link.
/// The module to link.
#[structopt(index = 1, value_name = "MODULE", parse(from_os_str))]
pub main: PathBuf,
pub module: PathBuf,
}

impl App {
Expand All @@ -57,15 +57,15 @@ impl App {
bail!("at least one import module must be specified");
}

let main_bytes = wat::parse_file(&self.main)
.with_context(|| format!("failed to parse main module `{}`", self.main.display()))?;
let module_bytes = wat::parse_file(&self.module)
.with_context(|| format!("failed to parse module `{}`", self.module.display()))?;

let main_module = Module::new(
self.main.file_name().unwrap().to_str().unwrap(),
&main_bytes,
let module = Module::new(
self.module.file_name().unwrap().to_str().unwrap(),
&module_bytes,
[],
)
.with_context(|| format!("failed to parse main module `{}`", self.main.display()))?;
.with_context(|| format!("failed to parse module `{}`", self.module.display()))?;

let import_bytes = self
.modules
Expand Down Expand Up @@ -118,8 +118,8 @@ impl App {

let linker = Linker::new(Profile::new());

let output = self.output.as_ref().unwrap_or(&self.main);
std::fs::write(output, linker.link(&main_module, &import_modules)?)
let output = self.output.as_ref().unwrap_or(&self.module);
std::fs::write(output, linker.link(&module, &import_modules)?)
.with_context(|| format!("failed to write to output module `{}`", output.display()))?;

Ok(())
Expand Down
104 changes: 44 additions & 60 deletions crates/wasmlink/src/linker.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -37,6 +37,7 @@ struct LinkedModule<'a> {
module_map: HashMap<&'a ModuleAdapter<'a>, (u32, Option<u32>)>,
instances: Vec<(u32, Vec<(&'a str, u32)>)>,
func_aliases: Vec<(u32, &'a str)>,
memory_aliases: Vec<(u32, &'a str)>,
table_aliases: Vec<(u32, &'a str)>,
segments: Vec<(u32, Vec<wasm_encoder::Element>)>,
exports: Vec<(&'a str, wasm_encoder::Export)>,
Expand Down Expand Up @@ -126,16 +127,32 @@ impl<'a> LinkedModule<'a> {
linked.instances.push((index, args));
}

// Instantiate the main module
let (main_index, _) = linked.instantiate(graph, NodeIndex::new(0), None)?;

// Re-export the start function
let start_index = linked.func_aliases.len() as u32;
linked.func_aliases.push((main_index, "_start"));
linked.exports.push((
"_start",
wasm_encoder::Export::Function(linked.imports.len() as u32 + start_index),
));
// Instantiate the root module
let (root_index, _) = linked.instantiate(graph, NodeIndex::new(0), None)?;

let root = &graph[NodeIndex::new(0)];

// Re-export all supported exports from the root module
for export in &root.module.exports {
match export.kind {
ExternalKind::Function => {
let func_index = linked.func_aliases.len() as u32;
linked.func_aliases.push((root_index, export.field));
linked.exports.push((
export.field,
wasm_encoder::Export::Function(linked.imports.len() as u32 + func_index),
));
}
ExternalKind::Memory => {
let memory_index = linked.memory_aliases.len() as u32;
linked.memory_aliases.push((root_index, export.field));
linked
.exports
.push((export.field, wasm_encoder::Export::Memory(memory_index)));
}
_ => {}
}
}

Ok(linked)
}
Expand Down Expand Up @@ -326,6 +343,10 @@ impl<'a> LinkedModule<'a> {
section.instance_export(*index, wasm_encoder::ItemKind::Table, name);
}

for (index, name) in &self.memory_aliases {
section.instance_export(*index, wasm_encoder::ItemKind::Memory, name);
}

module.section(&section);
}

Expand Down Expand Up @@ -370,21 +391,8 @@ impl Linker {
/// Links the given module with the given set of imported modules.
///
/// On success, returns a vector of bytes representing the linked module.
pub fn link(&self, main: &Module, imports: &HashMap<&str, Module>) -> Result<Vec<u8>> {
if !main.exports.iter().any(|e| match (e.field, e.kind) {
("_start", ExternalKind::Function) => {
let ty = main.func_type(e.index).unwrap();
ty.params.is_empty() && ty.returns.is_empty()
}
_ => false,
}) {
bail!(
"main module `{}` must export a start function that has no parameters or results",
main.name
);
}

let (graph, needs_runtime) = self.build_graph(main, imports)?;
pub fn link(&self, module: &Module, imports: &HashMap<&str, Module>) -> Result<Vec<u8>> {
let (graph, needs_runtime) = self.build_graph(module, imports)?;

let module = LinkedModule::new(&graph, needs_runtime, &self.profile)?;

Expand All @@ -393,16 +401,16 @@ impl Linker {

fn build_graph<'a>(
&self,
main: &'a Module,
module: &'a Module,
imports: &'a HashMap<&str, Module>,
) -> Result<(Graph<ModuleAdapter<'a>, ()>, bool)> {
let mut queue: Vec<(Option<petgraph::graph::NodeIndex>, &Module)> = Vec::new();
let mut seen = HashMap::new();
let mut graph: Graph<ModuleAdapter, ()> = Graph::new();

let mut needs_runtime = main.has_resources;
let mut needs_runtime = module.has_resources;

queue.push((None, main));
queue.push((None, module));

let mut next_resource_id = 0;

Expand Down Expand Up @@ -476,36 +484,6 @@ impl Linker {
mod test {
use super::*;

#[test]
fn it_errors_on_missing_main_function() -> Result<()> {
let bytes = wat::parse_str(r#"(module)"#)?;
let main = Module::new("main", &bytes, [])?;

let linker = Linker::new(Profile::new());

assert_eq!(
linker.link(&main, &HashMap::new()).unwrap_err().to_string(),
"main module `main` must export a start function that has no parameters or results"
);

Ok(())
}

#[test]
fn it_errors_on_incorrect_main_function() -> Result<()> {
let bytes = wat::parse_str(r#"(module (func (export "_start") (param i32)))"#)?;
let main = Module::new("main", &bytes, [])?;

let linker = Linker::new(Profile::new());

assert_eq!(
linker.link(&main, &HashMap::new()).unwrap_err().to_string(),
"main module `main` must export a start function that has no parameters or results"
);

Ok(())
}

#[test]
fn it_errors_on_missing_import() -> Result<()> {
let bytes = wat::parse_str(
Expand Down Expand Up @@ -743,7 +721,7 @@ mod test {
#[test]
fn it_links_with_interface() -> Result<()> {
let bytes = wat::parse_str(
r#"(module (import "a" "a" (func (param i32 i32))) (func (export "_start")) (func (export "canonical_abi_realloc") (param i32 i32 i32 i32) (result i32) unreachable))"#,
r#"(module (import "a" "a" (func (param i32 i32))) (func (export "_start")) (func (export "canonical_abi_realloc") (param i32 i32 i32 i32) (result i32) unreachable) (memory (export "memory") 0))"#,
)?;
let a = wat::parse_str(
r#"(module (import "wasi_snapshot_preview1" "a" (func)) (func (export "a") (param i32 i32)) (memory (export "memory") 0) (func (export "canonical_abi_realloc") (param i32 i32 i32 i32) (result i32) unreachable) (func (export "canonical_abi_free") (param i32 i32 i32)))"#,
Expand Down Expand Up @@ -777,8 +755,10 @@ mod test {
(func (;1;) (type 1))
(func (;2;) (type 2) (param i32 i32 i32 i32) (result i32)
unreachable)
(memory (;0;) 0)
(export \"_start\" (func 1))
(export \"canonical_abi_realloc\" (func 2)))
(export \"canonical_abi_realloc\" (func 2))
(export \"memory\" (memory 0)))
(module (;1;)
(type (;0;) (func))
(type (;1;) (func (param i32 i32)))
Expand Down Expand Up @@ -853,8 +833,12 @@ mod test {
(import \"$parent\" (instance 2))))
(alias 3 \"a\" (func (;1;)))
(alias 2 \"_start\" (func (;2;)))
(alias 2 \"canonical_abi_realloc\" (func (;3;)))
(alias 1 \"$funcs\" (table (;0;)))
(alias 2 \"memory\" (memory (;0;)))
(export \"_start\" (func 2))
(export \"canonical_abi_realloc\" (func 3))
(export \"memory\" (memory 0))
(elem (;0;) (i32.const 0) funcref (ref.func 1)))"
);

Expand Down