Add uninit intrinsic

Author: James Miller

src/libcore/unstable/intrinsics.rs

@@ -44,6 +44,9 @@ pub extern "rust-intrinsic" {
 
     pub fn init<T>() -> T;
 
+    #[cfg(not(stage0))]
+    pub unsafe fn uninit<T>() -> T;
+
     pub fn forget<T>(_: T) -> ();
 
     pub fn needs_drop<T>() -> bool;

src/librustc/middle/trans/foreign.rs

@@ -715,6 +715,9 @@ pub fn trans_intrinsic(ccx: @CrateContext,
                 Store(bcx, C_null(lltp_ty), fcx.llretptr.get());
             }
         }
+        ~"uninit" => {
+            // Do nothing, this is effectively a no-op
+        }
         ~"forget" => {}
         ~"transmute" => {
             let (in_type, out_type) = (substs.tys[0], substs.tys[1]);

src/librustc/middle/trans/type_use.rs

@@ -118,7 +118,7 @@ pub fn type_uses_for(ccx: @CrateContext, fn_id: def_id, n_tps: uint)
         if abi.is_intrinsic() {
             let flags = match *cx.ccx.sess.str_of(i.ident) {
                 ~"size_of"  | ~"pref_align_of" | ~"min_align_of" |
-                ~"init"     | ~"transmute"     | ~"move_val"     |
+                ~"uninit"   | ~"init" | ~"transmute" | ~"move_val" |
                 ~"move_val_init" => use_repr,
 
                 ~"get_tydesc" | ~"needs_drop" => use_tydesc,

src/librustc/middle/typeck/check/mod.rs

@@ -3447,6 +3447,7 @@ pub fn check_intrinsic_type(ccx: @mut CrateCtxt, it: @ast::foreign_item) {
       ~"size_of" |
       ~"pref_align_of" | ~"min_align_of" => (1u, ~[], ty::mk_uint()),
       ~"init" => (1u, ~[], param(ccx, 0u)),
+      ~"uninit" => (1u, ~[], param(ccx, 0u)),
       ~"forget" => (1u, ~[arg(param(ccx, 0u))], ty::mk_nil()),
       ~"transmute" => (2, ~[ arg(param(ccx, 0)) ], param(ccx, 1)),
       ~"move_val" | ~"move_val_init" => {

src/test/run-pass/intrinsic-uninit.rs

@@ -0,0 +1,19 @@
+// Copyright 2012 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+mod rusti {
+    #[abi = "rust-intrinsic"]
+    pub extern "rust-intrinsic" {
+        fn uninit<T>() -> T;
+    }
+}
+pub fn main() {
+    let _a : int = unsafe {rusti::uninit()};
+}