codegen: Be consistent about variadic signatures.

Fixes rust-lang#1216.

src/codegen/mod.rs

@@ -3249,21 +3249,13 @@ impl CodeGenerator for Function {
             abi => abi,
         };
 
-        let variadic = if signature.is_variadic() {
-            quote! { ... }
-        } else {
-            quote! {}
-        };
-
         let ident = ctx.rust_ident(canonical_name);
         let mut tokens = quote! { extern #abi };
         tokens.append("{\n");
         if !attributes.is_empty() {
             tokens.append_separated(attributes, "\n");
             tokens.append("\n");
         }
-        let mut args = args;
-        args.push(variadic);
         tokens.append(quote! {
             pub fn #ident ( #( #args ),* ) #ret;
         });
@@ -3719,7 +3711,7 @@ mod utils {
         use super::ToPtr;
 
         let mut unnamed_arguments = 0;
-        sig.argument_types().iter().map(|&(ref name, ty)| {
+        let mut args = sig.argument_types().iter().map(|&(ref name, ty)| {
             let arg_item = ctx.resolve_item(ty);
             let arg_ty = arg_item.kind().expect_type();
 
@@ -3766,6 +3758,12 @@ mod utils {
             quote! {
                 #arg_name : #arg_ty
             }
-        }).collect()
+        }).collect::<Vec<_>>();
+
+        if sig.is_variadic() {
+            args.push(quote! { ... })
+        }
+
+        args
     }
 }

tests/expectations/tests/issue-1216-variadic-member.rs

@@ -0,0 +1,42 @@
+/* automatically generated by rust-bindgen */
+
+#![allow(dead_code, non_snake_case, non_camel_case_types, non_upper_case_globals)]
+
+extern "C" {
+    pub fn f(a: ::std::os::raw::c_int, ...);
+}
+#[repr(C)]
+#[derive(Debug, Copy, Clone)]
+pub struct Foo {
+    pub f: ::std::option::Option<
+        unsafe extern "C" fn(
+            p: *mut ::std::os::raw::c_void,
+            obj: *mut ::std::os::raw::c_void,
+            a: ::std::os::raw::c_int,
+            ...
+        ),
+    >,
+}
+#[test]
+fn bindgen_test_layout_Foo() {
+    assert_eq!(
+        ::std::mem::size_of::<Foo>(),
+        8usize,
+        concat!("Size of: ", stringify!(Foo))
+    );
+    assert_eq!(
+        ::std::mem::align_of::<Foo>(),
+        8usize,
+        concat!("Alignment of ", stringify!(Foo))
+    );
+    assert_eq!(
+        unsafe { &(*(::std::ptr::null::<Foo>())).f as *const _ as usize },
+        0usize,
+        concat!("Offset of field: ", stringify!(Foo), "::", stringify!(f))
+    );
+}
+impl Default for Foo {
+    fn default() -> Self {
+        unsafe { ::std::mem::zeroed() }
+    }
+}

tests/headers/issue-1216-variadic-member.h

@@ -0,0 +1,4 @@
+void f(int a, ...);
+struct Foo {
+  void (*f)(void *p, void *obj, int a, ...);
+};