rustc: Always handle exported symbols on the wasm target

src/librustc_codegen_ssa/back/link.rs

@@ -1017,12 +1017,10 @@ fn link_args<'a, B: ArchiveBuilder<'a>>(cmd: &mut dyn Linker,
         }
     }
 
-    // If we're building a dynamic library then some platforms need to make sure
-    // that all symbols are exported correctly from the dynamic library.
-    if crate_type != config::CrateType::Executable ||
-       sess.target.target.options.is_like_emscripten {
-        cmd.export_symbols(tmpdir, crate_type);
-    }
+    // If we're building something like a dynamic library then some platforms
+    // need to make sure that all symbols are exported correctly from the
+    // dynamic library.
+    cmd.export_symbols(tmpdir, crate_type);
 
     // When linking a dynamic library, we put the metadata into a section of the
     // executable. This metadata is in a separate object file from the main

src/librustc_codegen_ssa/back/linker.rs

@@ -372,6 +372,11 @@ impl<'a> Linker for GccLinker<'a> {
     }
 
     fn export_symbols(&mut self, tmpdir: &Path, crate_type: CrateType) {
+        // Symbol visibility in object files typically takes care of this.
+        if crate_type == CrateType::Executable {
+            return;
+        }
+
         // If we're compiling a dylib, then we let symbol visibility in object
         // files to take care of whether they're exported or not.
         //
@@ -645,6 +650,11 @@ impl<'a> Linker for MsvcLinker<'a> {
     fn export_symbols(&mut self,
                       tmpdir: &Path,
                       crate_type: CrateType) {
+        // Symbol visibility takes care of this typically
+        if crate_type == CrateType::Executable {
+            return;
+        }
+
         let path = tmpdir.join("lib.def");
         let res: io::Result<()> = try {
             let mut f = BufWriter::new(File::create(&path)?);

src/test/run-make/wasm-export-all-symbols/Makefile

@@ -6,8 +6,14 @@ all:
 	$(RUSTC) bar.rs --target wasm32-unknown-unknown
 	$(RUSTC) foo.rs --target wasm32-unknown-unknown
 	$(NODE) verify.js $(TMPDIR)/foo.wasm
+	$(RUSTC) main.rs --target wasm32-unknown-unknown
+	$(NODE) verify.js $(TMPDIR)/main.wasm
 	$(RUSTC) bar.rs --target wasm32-unknown-unknown -O
 	$(RUSTC) foo.rs --target wasm32-unknown-unknown -O
 	$(NODE) verify.js $(TMPDIR)/foo.wasm
+	$(RUSTC) main.rs --target wasm32-unknown-unknown -O
+	$(NODE) verify.js $(TMPDIR)/main.wasm
 	$(RUSTC) foo.rs --target wasm32-unknown-unknown -C lto
 	$(NODE) verify.js $(TMPDIR)/foo.wasm
+	$(RUSTC) main.rs --target wasm32-unknown-unknown -C lto
+	$(NODE) verify.js $(TMPDIR)/main.wasm

src/test/run-make/wasm-export-all-symbols/main.rs

@@ -0,0 +1,3 @@
+extern crate bar;
+
+fn main() {}

src/test/run-make/wasm-export-all-symbols/verify.js

@@ -16,7 +16,13 @@ for (const entry of list) {
   nexports += 1;
 }
 
-if (nexports != 1)
-  throw new Error("should only have one function export");
 if (my_exports.foo === undefined)
   throw new Error("`foo` wasn't defined");
+
+if (my_exports.main === undefined) {
+  if (nexports != 1)
+    throw new Error("should only have one function export");
+} else {
+  if (nexports != 2)
+    throw new Error("should only have two function exports");
+}