Add tests exercising the dropflag checking functionality.

src/test/run-pass/drop-flag-sanity-check.rs

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+// Copyright 2015 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.
+
+// compile-flags: -Z force-dropflag-checks=on
+
+// Quick-and-dirty test to ensure -Z force-dropflag-checks=on works as
+// expected. Note that the inlined drop-flag is slated for removal
+// (RFC 320); when that happens, the -Z flag and this test should
+// simply be removed.
+//
+// See also drop-flag-skip-sanity-check.rs.
+
+use std::env;
+use std::old_io::process::{Command, ExitSignal, ExitStatus};
+
+fn main() {
+    let args: Vec<String> = env::args().collect();
+    if args.len() > 1 && args[1] == "test" {
+        return test();
+    }
+
+    let mut p = Command::new(&args[0]).arg("test").spawn().unwrap();
+    // The invocation should fail due to the drop-flag sanity check.
+    assert!(!p.wait().unwrap().success());
+}
+
+#[derive(Debug)]
+struct Corrupted {
+    x: u8
+}
+
+impl Drop for Corrupted {
+    fn drop(&mut self) { println!("dropping"); }
+}
+
+fn test() {
+    {
+        let mut c1 = Corrupted { x: 1 };
+        let mut c2 = Corrupted { x: 2 };
+        unsafe {
+            let p1 = &mut c1 as *mut Corrupted as *mut u8;
+            let p2 = &mut c2 as *mut Corrupted as *mut u8;
+            for i in 0..std::mem::size_of::<Corrupted>() {
+                // corrupt everything, *including the drop flag.
+                //
+                // (We corrupt via two different means to safeguard
+                // against the hypothetical assignment of the
+                // dtor_needed/dtor_done values to v and v+k.  that
+                // happen to match with one of the corruption values
+                // below.)
+                *p1.offset(i as isize) += 2;
+                *p2.offset(i as isize) += 3;
+            }
+        }
+        // Here, at the end of the scope of `c1` and `c2`, the
+        // drop-glue should detect the corruption of (at least one of)
+        // the drop-flags.
+    }
+    println!("We should never get here.");
+}

src/test/run-pass/drop-flag-skip-sanity-check.rs

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+// Copyright 2015 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.
+
+// compile-flags: -Z force-dropflag-checks=off
+
+// Quick-and-dirty test to ensure -Z force-dropflag-checks=off works as
+// expected. Note that the inlined drop-flag is slated for removal
+// (RFC 320); when that happens, the -Z flag and this test should
+// simply be removed.
+//
+// See also drop-flag-sanity-check.rs.
+
+use std::env;
+use std::old_io::process::{Command, ExitSignal, ExitStatus};
+
+fn main() {
+    let args: Vec<String> = env::args().collect();
+    if args.len() > 1 && args[1] == "test" {
+        return test();
+    }
+
+    let mut p = Command::new(&args[0]).arg("test").spawn().unwrap();
+    // Invocatinn should succeed as drop-flag sanity check is skipped.
+    assert!(p.wait().unwrap().success());
+}
+
+#[derive(Debug)]
+struct Corrupted {
+    x: u8
+}
+
+impl Drop for Corrupted {
+    fn drop(&mut self) { println!("dropping"); }
+}
+
+fn test() {
+    {
+        let mut c1 = Corrupted { x: 1 };
+        let mut c2 = Corrupted { x: 2 };
+        unsafe {
+            let p1 = &mut c1 as *mut Corrupted as *mut u8;
+            let p2 = &mut c2 as *mut Corrupted as *mut u8;
+            for i in 0..std::mem::size_of::<Corrupted>() {
+                // corrupt everything, *including the drop flag.
+                //
+                // (We corrupt via two different means to safeguard
+                // against the hypothetical assignment of the
+                // dtor_needed/dtor_done values to v and v+k.  that
+                // happen to match with one of the corruption values
+                // below.)
+                *p1.offset(i as isize) += 2;
+                *p2.offset(i as isize) += 3;
+            }
+        }
+        // Here, at the end of the scope of `c1` and `c2`, the
+        // drop-glue should detect the corruption of (at least one of)
+        // the drop-flags.
+    }
+    println!("We should never get here.");
+}