Merge #598

598: Hello world r=philberty a=philberty

```rust
extern "C" {
    fn puts(s: *const i8);
}

fn main() {
    unsafe {
        let a = "Hello World\0";
        let b = a as *const str;
        let c = b as *const i8;
        puts(c);
    }
}
```

Fixes #421

Co-authored-by: Philip Herron <philip.herron@embecosm.com>

1 files changed, 7 insertions, 0 deletions

diff --git a/gcc/rust/rust-backend.h b/gcc/rust/rust-backend.h
index 1dd4aba..be23fd3 100644
--- a/gcc/rust/rust-backend.h
+++ b/gcc/rust/rust-backend.h
@@ -163,6 +163,13 @@ public:
 		 Btype *result_struct, Location location)
     = 0;
 
+  virtual Btype *
+  function_type_varadic (const Btyped_identifier &receiver,
+			 const std::vector<Btyped_identifier> &parameters,
+			 const std::vector<Btyped_identifier> &results,
+			 Btype *result_struct, Location location)
+    = 0;
+
   virtual Btype *function_ptr_type (Btype *result,
 				    const std::vector<Btype *> &praameters,
 				    Location location)