Add support for bindings to overloaded functions

This commit (re)adds support for generating bindings to overloaded
functions. First, we use the symbol name instead of the canonical name
when checking if we have already generated bindings for a given
function. Second, we add a map from canonical names to number of times
we have generated a function with that canonical name. We increment this
number every time we generate a function. When the number is greater
than zero, we append it to the function name so that overloaded
functions get a unique Rust symbol.

Author: fitzgen

src/codegen/mod.rs

@@ -21,6 +21,7 @@ use self::helpers::{BlobTyBuilder, attributes};
 use std::borrow::Cow;
 use std::collections::HashSet;
 use std::collections::hash_map::{Entry, HashMap};
+use std::fmt::Write;
 use std::mem;
 use std::ops;
 use syntax::abi::Abi;
@@ -57,6 +58,11 @@ struct CodegenResult {
     /// Being these two different declarations.
     functions_seen: HashSet<String>,
     vars_seen: HashSet<String>,
+
+    /// Used for making bindings to overloaded functions. Maps from a canonical
+    /// function name to the number of overloads we have already codegen'd for
+    /// that name. This lets us give each overload a unique suffix.
+    overload_counters: HashMap<String, u32>,
 }
 
 impl CodegenResult {
@@ -67,6 +73,7 @@ impl CodegenResult {
             items_seen: Default::default(),
             functions_seen: Default::default(),
             vars_seen: Default::default(),
+            overload_counters: Default::default(),
         }
     }
 
@@ -90,6 +97,16 @@ impl CodegenResult {
         self.functions_seen.insert(name.into());
     }
 
+    /// Get the overload number for the given function name. Increments the
+    /// counter internally so the next time we ask for the overload for this
+    /// name, we get the incremented value, and so on.
+    fn overload_number(&mut self, name: &str) -> u32 {
+        let mut counter = self.overload_counters.entry(name.into()).or_insert(0);
+        let number = *counter;
+        *counter += 1;
+        number
+    }
+
     fn seen_var(&self, name: &str) -> bool {
         self.vars_seen.contains(name)
     }
@@ -1803,14 +1820,19 @@ impl CodeGenerator for Function {
                result: &mut CodegenResult,
                item: &Item) {
         let name = self.name();
-        let canonical_name = item.canonical_name(ctx);
+        let mut canonical_name = item.canonical_name(ctx);
+        let mangled_name = self.mangled_name();
 
-        // TODO: Maybe warn here if there's a type/argument mismatch, or
-        // something?
-        if result.seen_function(&canonical_name) {
-            return;
+        {
+            let seen_symbol_name = mangled_name.unwrap_or(&canonical_name);
+
+            // TODO: Maybe warn here if there's a type/argument mismatch, or
+            // something?
+            if result.seen_function(seen_symbol_name) {
+                return;
+            }
+            result.saw_function(seen_symbol_name);
         }
-        result.saw_function(&canonical_name);
 
         let signature_item = ctx.resolve_item(self.signature());
         let signature = signature_item.kind().expect_type();
@@ -1827,7 +1849,7 @@ impl CodeGenerator for Function {
             attributes.push(attributes::doc(comment));
         }
 
-        if let Some(mangled) = self.mangled_name() {
+        if let Some(mangled) = mangled_name {
             attributes.push(attributes::link_name(mangled));
         } else if name != canonical_name {
             attributes.push(attributes::link_name(name));
@@ -1836,6 +1858,13 @@ impl CodeGenerator for Function {
         let foreign_item_kind =
             ast::ForeignItemKind::Fn(fndecl, ast::Generics::default());
 
+        // Handle overloaded functions by giving each overload its own unique
+        // suffix.
+        let times_seen = result.overload_number(&canonical_name);
+        if times_seen > 0 {
+            write!(&mut canonical_name, "{}", times_seen).unwrap();
+        }
+
         let foreign_item = ast::ForeignItem {
             ident: ctx.rust_ident_raw(&canonical_name),
             attrs: attributes,

tests/expectations/tests/overloading.rs

@@ -0,0 +1,23 @@
+/* automatically generated by rust-bindgen */
+
+
+#![allow(non_snake_case)]
+
+
+extern "C" {
+    #[link_name = "_Z8Evaluatec"]
+    pub fn Evaluate(r: ::std::os::raw::c_char) -> bool;
+}
+extern "C" {
+    #[link_name = "_Z8Evaluateii"]
+    pub fn Evaluate1(x: ::std::os::raw::c_int, y: ::std::os::raw::c_int)
+     -> bool;
+}
+extern "C" {
+    #[link_name = "_ZN3foo10MyFunctionEv"]
+    pub fn MyFunction();
+}
+extern "C" {
+    #[link_name = "_ZN3bar10MyFunctionEv"]
+    pub fn MyFunction1();
+}

tests/headers/overloading.hpp

@@ -0,0 +1,9 @@
+extern bool Evaluate(char r);
+extern bool Evaluate(int x, int y);
+
+namespace foo {
+    extern void MyFunction();
+}
+namespace bar {
+    extern void MyFunction();
+}