Support defining C compatible variadic functions

Add support for defining C compatible variadic functions in unsafe rust
with extern "C".

src/librustdoc/clean/mod.rs

@@ -1752,7 +1752,6 @@ impl Clean<Item> for doctree::Function {
 pub struct FnDecl {
     pub inputs: Arguments,
     pub output: FunctionRetTy,
-    pub variadic: bool,
     pub attrs: Attributes,
 }
 
@@ -1831,7 +1830,6 @@ impl<'a, A: Copy> Clean<FnDecl> for (&'a hir::FnDecl, A)
         FnDecl {
             inputs: (&self.0.inputs[..], self.1).clean(cx),
             output: self.0.output.clean(cx),
-            variadic: self.0.variadic,
             attrs: Attributes::default()
         }
     }
@@ -1849,7 +1847,6 @@ impl<'a, 'tcx> Clean<FnDecl> for (DefId, ty::PolyFnSig<'tcx>) {
         FnDecl {
             output: Return(sig.skip_binder().output().clean(cx)),
             attrs: Attributes::default(),
-            variadic: sig.skip_binder().variadic,
             inputs: Arguments {
                 values: sig.skip_binder().inputs().iter().map(|t| {
                     Argument {
@@ -2252,6 +2249,7 @@ pub enum Type {
     Slice(Box<Type>),
     Array(Box<Type>, String),
     Never,
+    CVarArgs,
     Unique(Box<Type>),
     RawPointer(Mutability, Box<Type>),
     BorrowedRef {
@@ -2290,6 +2288,7 @@ pub enum PrimitiveType {
     Reference,
     Fn,
     Never,
+    CVarArgs,
 }
 
 #[derive(Clone, RustcEncodable, RustcDecodable, Copy, Debug)]
@@ -2469,6 +2468,7 @@ impl PrimitiveType {
             Reference => "reference",
             Fn => "fn",
             Never => "never",
+            CVarArgs => "...",
         }
     }
 
@@ -2518,6 +2518,7 @@ impl Clean<Type> for hir::Ty {
 
         match self.node {
             TyKind::Never => Never,
+            TyKind::CVarArgs(_) => CVarArgs,
             TyKind::Ptr(ref m) => RawPointer(m.mutbl.clean(cx), box m.ty.clean(cx)),
             TyKind::Rptr(ref l, ref m) => {
                 let lifetime = if l.is_elided() {
@@ -3654,6 +3655,7 @@ fn build_deref_target_impls(cx: &DocContext<'_, '_, '_>,
             Reference => None,
             Fn => None,
             Never => None,
+            CVarArgs => tcx.lang_items().va_list(),
         };
         if let Some(did) = did {
             if !did.is_local() {

src/librustdoc/html/format.rs

@@ -609,6 +609,7 @@ fn fmt_type(t: &clean::Type, f: &mut fmt::Formatter<'_>, use_absolute: bool) ->
             primitive_link(f, PrimitiveType::Array, &format!("; {}]", n))
         }
         clean::Never => primitive_link(f, PrimitiveType::Never, "!"),
+        clean::CVarArgs => primitive_link(f, PrimitiveType::CVarArgs, "..."),
         clean::RawPointer(m, ref t) => {
             match **t {
                 clean::Generic(_) | clean::ResolvedPath {is_generic: true, ..} => {
@@ -834,18 +835,10 @@ impl fmt::Display for clean::FunctionRetTy {
 
 impl fmt::Display for clean::FnDecl {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        if self.variadic {
-            if f.alternate() {
-                write!(f, "({args:#}, ...){arrow:#}", args = self.inputs, arrow = self.output)
-            } else {
-                write!(f, "({args}, ...){arrow}", args = self.inputs, arrow = self.output)
-            }
+        if f.alternate() {
+            write!(f, "({args:#}){arrow:#}", args = self.inputs, arrow = self.output)
         } else {
-            if f.alternate() {
-                write!(f, "({args:#}){arrow:#}", args = self.inputs, arrow = self.output)
-            } else {
-                write!(f, "({args}){arrow}", args = self.inputs, arrow = self.output)
-            }
+            write!(f, "({args}){arrow}", args = self.inputs, arrow = self.output)
         }
     }
 }
@@ -907,12 +900,7 @@ impl<'a> fmt::Display for Function<'a> {
             }
         }
 
-        let mut args_plain = format!("({})", args_plain);
-
-        if decl.variadic {
-            args.push_str(",<br> ...");
-            args_plain.push_str(", ...");
-        }
+        let args_plain = format!("({})", args_plain);
 
         let output = if let hir::IsAsync::Async = asyncness {
             Cow::Owned(decl.sugared_async_return_type())