Auto merge of #1063 - liranringel:disable-mangling-if-link-name-is-specified, r=emilio

Tell LLVM to not mangle names if they're already mangled

LLVM mangles the name by default but functions are already mangled because the `link_name` attribute's value is mangled.
Prefixing the name with `\u{1}` should tell LLVM to not mangle it.

I originally thought it's a bug in rustc, but it was clarified here: rust-lang/rust#45073

Author: bors-servo

src/codegen/helpers.rs

@@ -45,6 +45,9 @@ pub mod attributes {
     }
 
     pub fn link_name(name: &str) -> quote::Tokens {
+        // LLVM mangles the name by default but it's already mangled.
+        // Prefixing the name with \u{1} should tell LLVM to not mangle it.
+        let name = format!("\u{1}{}", name);
         quote! {
             #[link_name = #name]
         }

src/ir/context.rs

@@ -391,9 +391,6 @@ pub struct BindgenContext {
     /// bitfield allocation units computed. Drained in `compute_bitfield_units`.
     need_bitfield_allocation: Vec<ItemId>,
 
-    /// Whether we need the mangling hack which removes the prefixing underscore.
-    needs_mangling_hack: bool,
-
     /// The set of (`ItemId`s of) types that can't derive debug.
     ///
     /// This is populated when we enter codegen by `compute_cannot_derive_debug`
@@ -558,15 +555,6 @@ impl BindgenContext {
             ).expect("TranslationUnit::parse failed")
         };
 
-        // Mac os, iOS and Win32 need __ for mangled symbols but rust will
-        // automatically prepend the extra _.
-        //
-        // We need to make sure that we don't include __ because rust will turn
-        // into ___.
-        let needs_mangling_hack = effective_target.contains("darwin") ||
-            effective_target.contains("ios") ||
-            effective_target == "i686-pc-win32";
-
         let root_module = Self::build_root_module(ItemId(0));
         let root_module_id = root_module.id().as_module_id_unchecked();
 
@@ -592,7 +580,6 @@ impl BindgenContext {
             codegen_items: None,
             used_template_parameters: None,
             need_bitfield_allocation: Default::default(),
-            needs_mangling_hack: needs_mangling_hack,
             cannot_derive_debug: None,
             cannot_derive_default: None,
             cannot_derive_copy: None,
@@ -1415,11 +1402,6 @@ impl BindgenContext {
         Item::new(id, None, None, id, ItemKind::Module(module))
     }
 
-    /// Returns the target triple bindgen is running over.
-    pub fn needs_mangling_hack(&self) -> bool {
-        self.needs_mangling_hack
-    }
-
     /// Get the root module.
     pub fn root_module(&self) -> ModuleId {
         self.root_module

src/ir/function.rs

@@ -206,23 +206,6 @@ fn get_abi(cc: CXCallingConv) -> Abi {
     }
 }
 
-fn mangling_hack_if_needed(ctx: &BindgenContext, symbol: &mut String) {
-    if ctx.needs_mangling_hack() {
-        match symbol.chars().next().unwrap() {
-            // Stripping leading underscore for all names on Darwin and
-            // C linkage functions on Win32.
-            '_' => {
-                symbol.remove(0);
-            }
-            // Stop Rust from prepending underscore for variables on Win32.
-            '?' => {
-                symbol.insert(0, '\x01');
-            }
-            _ => {}
-        }
-    }
-}
-
 /// Get the mangled name for the cursor's referent.
 pub fn cursor_mangling(
     ctx: &BindgenContext,
@@ -241,8 +224,7 @@ pub fn cursor_mangling(
     }
 
     if let Ok(mut manglings) = cursor.cxx_manglings() {
-        if let Some(mut m) = manglings.pop() {
-            mangling_hack_if_needed(ctx, &mut m);
+        if let Some(m) = manglings.pop() {
             return Some(m);
         }
     }
@@ -252,8 +234,6 @@ pub fn cursor_mangling(
         return None;
     }
 
-    mangling_hack_if_needed(ctx, &mut mangling);
-
     if cursor.kind() == clang_sys::CXCursor_Destructor {
         // With old (3.8-) libclang versions, and the Itanium ABI, clang returns
         // the "destructor group 0" symbol, which means that it'll try to free

tests/expectations/tests/arg_keyword.rs

@@ -5,6 +5,6 @@
 
 
 extern "C" {
-    #[link_name = "_Z3fooPKc"]
+    #[link_name = "\u{1}_Z3fooPKc"]
     pub fn foo(type_: *const ::std::os::raw::c_char);
 }

tests/expectations/tests/bitfield-method-same-name.rs

@@ -24,15 +24,15 @@ fn bindgen_test_layout_Foo() {
     );
 }
 extern "C" {
-    #[link_name = "_ZN3Foo4typeEv"]
+    #[link_name = "\u{1}_ZN3Foo4typeEv"]
     pub fn Foo_type(this: *mut Foo) -> ::std::os::raw::c_char;
 }
 extern "C" {
-    #[link_name = "_ZN3Foo9set_type_Ec"]
+    #[link_name = "\u{1}_ZN3Foo9set_type_Ec"]
     pub fn Foo_set_type_(this: *mut Foo, c: ::std::os::raw::c_char);
 }
 extern "C" {
-    #[link_name = "_ZN3Foo8set_typeEc"]
+    #[link_name = "\u{1}_ZN3Foo8set_typeEc"]
     pub fn Foo_set_type(this: *mut Foo, c: ::std::os::raw::c_char);
 }
 impl Clone for Foo {

tests/expectations/tests/bitfield_large_overflow.rs

@@ -28,6 +28,6 @@ impl Clone for _bindgen_ty_1 {
     }
 }
 extern "C" {
-    #[link_name = "a"]
+    #[link_name = "\u{1}a"]
     pub static mut a: _bindgen_ty_1;
 }

tests/expectations/tests/canonical_path_without_namespacing.rs

@@ -20,6 +20,6 @@ impl Clone for Bar {
     fn clone(&self) -> Self { *self }
 }
 extern "C" {
-    #[link_name = "_Z3bazPN3foo3BarE"]
+    #[link_name = "\u{1}_Z3bazPN3foo3BarE"]
     pub fn baz(arg1: *mut Bar);
 }

tests/expectations/tests/class.rs

@@ -245,23 +245,23 @@ fn bindgen_test_layout_RealAbstractionWithTonsOfMethods() {
                 RealAbstractionWithTonsOfMethods ) ));
 }
 extern "C" {
-    #[link_name = "_ZNK32RealAbstractionWithTonsOfMethods3barEv"]
+    #[link_name = "\u{1}_ZNK32RealAbstractionWithTonsOfMethods3barEv"]
     pub fn RealAbstractionWithTonsOfMethods_bar(this:
                                                     *const RealAbstractionWithTonsOfMethods);
 }
 extern "C" {
-    #[link_name = "_ZN32RealAbstractionWithTonsOfMethods3barEv"]
+    #[link_name = "\u{1}_ZN32RealAbstractionWithTonsOfMethods3barEv"]
     pub fn RealAbstractionWithTonsOfMethods_bar1(this:
                                                      *mut RealAbstractionWithTonsOfMethods);
 }
 extern "C" {
-    #[link_name = "_ZN32RealAbstractionWithTonsOfMethods3barEi"]
+    #[link_name = "\u{1}_ZN32RealAbstractionWithTonsOfMethods3barEi"]
     pub fn RealAbstractionWithTonsOfMethods_bar2(this:
                                                      *mut RealAbstractionWithTonsOfMethods,
                                                  foo: ::std::os::raw::c_int);
 }
 extern "C" {
-    #[link_name = "_ZN32RealAbstractionWithTonsOfMethods3staEv"]
+    #[link_name = "\u{1}_ZN32RealAbstractionWithTonsOfMethods3staEv"]
     pub fn RealAbstractionWithTonsOfMethods_sta();
 }
 impl Clone for RealAbstractionWithTonsOfMethods {

tests/expectations/tests/class_1_0.rs

@@ -395,22 +395,22 @@ fn bindgen_test_layout_RealAbstractionWithTonsOfMethods() {
     );
 }
 extern "C" {
-    #[link_name = "_ZNK32RealAbstractionWithTonsOfMethods3barEv"]
+    #[link_name = "\u{1}_ZNK32RealAbstractionWithTonsOfMethods3barEv"]
     pub fn RealAbstractionWithTonsOfMethods_bar(this: *const RealAbstractionWithTonsOfMethods);
 }
 extern "C" {
-    #[link_name = "_ZN32RealAbstractionWithTonsOfMethods3barEv"]
+    #[link_name = "\u{1}_ZN32RealAbstractionWithTonsOfMethods3barEv"]
     pub fn RealAbstractionWithTonsOfMethods_bar1(this: *mut RealAbstractionWithTonsOfMethods);
 }
 extern "C" {
-    #[link_name = "_ZN32RealAbstractionWithTonsOfMethods3barEi"]
+    #[link_name = "\u{1}_ZN32RealAbstractionWithTonsOfMethods3barEi"]
     pub fn RealAbstractionWithTonsOfMethods_bar2(
         this: *mut RealAbstractionWithTonsOfMethods,
         foo: ::std::os::raw::c_int,
     );
 }
 extern "C" {
-    #[link_name = "_ZN32RealAbstractionWithTonsOfMethods3staEv"]
+    #[link_name = "\u{1}_ZN32RealAbstractionWithTonsOfMethods3staEv"]
     pub fn RealAbstractionWithTonsOfMethods_sta();
 }
 impl Clone for RealAbstractionWithTonsOfMethods {

tests/expectations/tests/class_nested.rs

@@ -115,7 +115,7 @@ impl Clone for A_C {
     }
 }
 extern "C" {
-    #[link_name = "var"]
+    #[link_name = "\u{1}var"]
     pub static mut var: A_B;
 }
 #[test]
@@ -131,7 +131,7 @@ fn __bindgen_test_layout_A_D_open0_int_close0_instantiation() {
     assert_eq ! ( :: std :: mem :: align_of :: < A_D < :: std :: os :: raw :: c_int > > ( ) , 4usize , concat ! ( "Alignment of template specialization: " , stringify ! ( A_D < :: std :: os :: raw :: c_int > ) ) );
 }
 extern "C" {
-    #[link_name = "baz"]
+    #[link_name = "\u{1}baz"]
     pub static mut baz: A_D<::std::os::raw::c_int>;
 }
 #[repr(C)]