feat(compiler): Allow exporting the function table

cli/bin/grain.js

@@ -146,6 +146,10 @@ class GrainCommand extends commander.Command {
       "--use-start-section",
       "replaces the _start export with a start section during linking"
     );
+    cmd.forwardOption(
+      "--export-function-table",
+      "causes the function table to be exported under the given name"
+    );
     cmd.forwardOption(
       "--no-pervasives",
       "don't automatically import the Grain Pervasives module"

compiler/src/linking/link.re

@@ -698,6 +698,17 @@ let link_all = (linked_mod, dependencies, signature) => {
     Type.funcref,
   );
 
+  switch (Grain_utils.Config.export_function_table^) {
+  | Some(name) =>
+    ignore @@
+    Export.add_table_export(
+      linked_mod,
+      Comp_utils.grain_global_function_table,
+      name,
+    )
+  | None => ()
+  };
+
   let (initial_memory, maximum_memory) =
     switch (Config.initial_memory_pages^, Config.maximum_memory_pages^) {
     | (initial_memory, Some(maximum_memory)) => (

compiler/src/utils/config.re

@@ -545,6 +545,14 @@ let use_start_section =
     false,
   );
 
+let export_function_table =
+  opt(
+    ~names=["export-function-table"],
+    ~conv=option_conv(Cmdliner.Arg.string),
+    ~doc="Causes the function table to be exported under the given name.",
+    None,
+  );
+
 let elide_type_info =
   toggle_flag(
     ~names=["elide-type-info"],

compiler/src/utils/config.rei

@@ -40,6 +40,9 @@ let wasi_polyfill: ref(option(string));
 
 let use_start_section: ref(bool);
 
+/** Weather to export the function table under a specifed name */
+let export_function_table: ref(option(string));
+
 /** Compilation profile, e.g. release for production builds */
 
 let profile: ref(option(profile));

compiler/test/suites/linking.re

@@ -122,6 +122,35 @@ describe("linking", ({test, testSkip}) => {
     );
   });
 
+  test("export_function_table", ({expect}) => {
+    let name = "export_function_table";
+    let outfile = wasmfile(name);
+    ignore @@
+    compile(
+      ~config_fn=
+        () => {Grain_utils.Config.export_function_table := Some("funcTable")},
+      name,
+      {|module Test; print("Hello, world!")|},
+    );
+    let ic = open_in_bin(outfile);
+    let sections = Grain_utils.Wasm_utils.get_wasm_sections(ic);
+    close_in(ic);
+    let export_sections =
+      List.find_map(
+        (sec: Grain_utils.Wasm_utils.wasm_bin_section) =>
+          switch (sec) {
+          | {sec_type: Export(exports)} => Some(exports)
+          | _ => None
+          },
+        sections,
+      );
+    expect.option(export_sections).toBeSome();
+    expect.list(Option.get(export_sections)).toContainEqual(
+      ~equals=tuple_equal,
+      (WasmTable, "funcTable"),
+    );
+  });
+
   test("import_memory", ({expect}) => {
     let name = "import_memory";
     let outfile = wasmfile(name);