DoubleEndedIterator for Args

The number of arguments given to a process is always known, which
makes implementing DoubleEndedIterator possible.

That way, the Iterator::rev() method becomes usable, among others.

Signed-off-by: Sebastian Thiel <byronimo@gmail.com>

Tidy for DoubleEndedIterator

I chose to not create a new feature for it, even though
technically, this makes me lie about the original availability
of the implementation.

Verify with @alexchrichton

Setup feature flag for new std::env::Args iterators

Add test for Args reverse iterator

It's somewhat depending on the input of the test program,
but made in such a way that should be somewhat flexible to changes
to the way it is called.

Deduplicate windows ArgsOS code for DEI

DEI = DoubleEndedIterator

Move env::args().rev() test to run-pass

It must be controlling it's arguments for full isolation.

Remove superfluous feature name

Assert all arguments returned by env::args().rev()

Let's be very sure it works as we expect, why take chances.

Fix rval of os_string_from_ptr

A trait cannot be returned, but only the corresponding object.

Deref pointers to actually operate on the argument

Put unsafe to correct location

1 files changed, 44 insertions, 0 deletions

diff --git a/src/test/run-pass/env-args-reverse-iterator.rs b/src/test/run-pass/env-args-reverse-iterator.rs
new file mode 100644
index 00000000000..d22fa6494f0
--- /dev/null
+++ b/src/test/run-pass/env-args-reverse-iterator.rs
@@ -0,0 +1,44 @@
+// Copyright 2014 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.
+
+use std::env::args;
+use std::process::Command;
+
+fn assert_reverse_iterator_for_program_arguments(program_name: &str) {
+    let args: Vec<_> = args().rev().collect();
+
+    assert!(args.len() == 4);
+    assert_eq!(args[0], "c");
+    assert_eq!(args[1], "b");
+    assert_eq!(args[2], "a");
+    assert_eq!(args[3], program_name);
+
+    println!("passed");
+}
+
+fn main() {
+    let mut args = args();
+    let me = args.next().unwrap();
+
+    if let Some(_) = args.next() {
+        assert_reverse_iterator_for_program_arguments(&me);
+        return
+    }
+
+    let output = Command::new(&me)
+        .arg("a")
+        .arg("b")
+        .arg("c")
+        .output()
+        .unwrap();
+    assert!(output.status.success());
+    assert!(output.stderr.is_empty());
+    assert_eq!(output.stdout, b"passed\n");
+}