rollup merge of #22482: alexcrichton/cstr-changes

This commit is an implementation of [RFC 592][r592] and [RFC 840][r840]. These
two RFCs tweak the behavior of `CString` and add a new `CStr` unsized slice type
to the module.

[r592]: https://github.com/rust-lang/rfcs/blob/master/text/0592-c-str-deref.md
[r840]: https://github.com/rust-lang/rfcs/blob/master/text/0840-no-panic-in-c-string.md

The new `CStr` type is only constructable via two methods:

1. By `deref`'ing from a `CString`
2. Unsafely via `CStr::from_ptr`

The purpose of `CStr` is to be an unsized type which is a thin pointer to a
`libc::c_char` (currently it is a fat pointer slice due to implementation
limitations). Strings from C can be safely represented with a `CStr` and an
appropriate lifetime as well. Consumers of `&CString` should now consume `&CStr`
instead to allow producers to pass in C-originating strings instead of just
Rust-allocated strings.

A new constructor was added to `CString`, `new`, which takes `T: IntoBytes`
instead of separate `from_slice` and `from_vec` methods (both have been
deprecated in favor of `new`). The `new` method returns a `Result` instead of
panicking.  The error variant contains the relevant information about where the
error happened and bytes (if present). Conversions are provided to the
`io::Error` and `old_io::IoError` types via the `FromError` trait which
translate to `InvalidInput`.

This is a breaking change due to the modification of existing `#[unstable]` APIs
and new deprecation, and more detailed information can be found in the two RFCs.
Notable breakage includes:

* All construction of `CString` now needs to use `new` and handle the outgoing
  `Result`.
* Usage of `CString` as a byte slice now explicitly needs a `.as_bytes()` call.
* The `as_slice*` methods have been removed in favor of just having the
  `as_bytes*` methods.

Closes #22469
Closes #22470
[breaking-change]

1 files changed, 5 insertions, 4 deletions

diff --git a/src/libstd/rt/args.rs b/src/libstd/rt/args.rs
index c2f5133eaf3..61f5bd0f013 100644
--- a/src/libstd/rt/args.rs
+++ b/src/libstd/rt/args.rs
@@ -49,7 +49,7 @@ mod imp {
 
     use libc;
     use mem;
-    use ffi;
+    use ffi::CStr;
 
     use sync::{StaticMutex, MUTEX_INIT};
 
@@ -96,10 +96,11 @@ mod imp {
         unsafe { mem::transmute(&GLOBAL_ARGS_PTR) }
     }
 
-    unsafe fn load_argc_and_argv(argc: int, argv: *const *const u8) -> Vec<Vec<u8>> {
+    unsafe fn load_argc_and_argv(argc: isize,
+                                 argv: *const *const u8) -> Vec<Vec<u8>> {
         let argv = argv as *const *const libc::c_char;
-        (0..argc as uint).map(|i| {
-            ffi::c_str_to_bytes(&*argv.offset(i as int)).to_vec()
+        (0..argc).map(|i| {
+            CStr::from_ptr(*argv.offset(i)).to_bytes().to_vec()
         }).collect()
     }