1 files changed, 9 insertions, 13 deletions
diff --git a/src/passes/ExtractFunction.cpp b/src/passes/ExtractFunction.cpp
index 7259f399d..8a97ced8e 100644
--- a/src/passes/ExtractFunction.cpp
+++ b/src/passes/ExtractFunction.cpp
@@ -23,22 +23,18 @@
 
 namespace wasm {
 
-
 struct ExtractFunction : public Pass {
   void run(PassRunner* runner, Module* module) override {
-    auto* leave = getenv("BINARYEN_EXTRACT");
-    if (!leave) {
-      std::cerr << "usage: set BINARYEN_EXTRACT in the env\n";
-      abort();
-    }
-    Name LEAVE(leave);
-    std::cerr << "extracting " << LEAVE << "\n";
+    Name name = runner->options.getArgument("extract", "ExtractFunction usage:  wasm-opt --pass-arg=extract:FUNCTION_NAME");
+    std::cerr << "extracting " << name << "\n";
     bool found = false;
     for (auto& func : module->functions) {
-      if (func->name != LEAVE) {
-        // wipe out all the contents
+      if (func->name != name) {
+        // Turn it into an import.
+        func->module = "env";
+        func->base = func->name;
         func->vars.clear();
-        func->body = module->allocator.alloc<Unreachable>();
+        func->body = nullptr;
       } else {
         found = true;
       }
@@ -53,8 +49,8 @@ struct ExtractFunction : public Pass {
     // leave just an export for the thing we want
     module->exports.clear();
     auto* export_ = new Export;
-    export_->name = LEAVE;
-    export_->value = LEAVE;
+    export_->name = name;
+    export_->value = name;
     export_->kind = ExternalKind::Function;
     module->addExport(export_);
   }