std: Redesign c_str and c_vec

This commit is an implementation of [RFC 494][rfc] which removes the entire
`std::c_vec` module and redesigns the `std::c_str` module as `std::ffi`.

[rfc]: https://github.com/rust-lang/rfcs/blob/master/text/0494-c_str-and-c_vec-stability.md

The interface of the new `CString` is outlined in the linked RFC, the primary
changes being:

* The `ToCStr` trait is gone, meaning the `with_c_str` and `to_c_str` methods
  are now gone. These two methods are replaced with a `CString::from_slice`
  method.
* The `CString` type is now just a wrapper around `Vec<u8>` with a static
  guarantee that there is a trailing nul byte with no internal nul bytes. This
  means that `CString` now implements `Deref<Target = [c_char]>`, which is where
  it gains most of its methods from. A few helper methods are added to acquire a
  slice of `u8` instead of `c_char`, as well as including a slice with the
  trailing nul byte if necessary.
* All usage of non-owned `CString` values is now done via two functions inside
  of `std::ffi`, called `c_str_to_bytes` and `c_str_to_bytes_with_nul`. These
  functions are now the one method used to convert a `*const c_char` to a Rust
  slice of `u8`.

Many more details, including newly deprecated methods, can be found linked in
the RFC. This is a:

[breaking-change]
Closes #20444

1 files changed, 15 insertions, 16 deletions

diff --git a/src/libstd/sys/windows/process.rs b/src/libstd/sys/windows/process.rs
index 81e8f974a12..9b3f2ca0373 100644
--- a/src/libstd/sys/windows/process.rs
+++ b/src/libstd/sys/windows/process.rs
@@ -10,27 +10,26 @@
 
 use prelude::v1::*;
 
+use collections;
+use ffi::CString;
+use hash::Hash;
+use io::fs::PathExtensions;
+use io::process::{ProcessExit, ExitStatus, ExitSignal};
+use io::{IoResult, IoError};
+use io;
 use libc::{pid_t, c_void, c_int};
 use libc;
-use c_str::{CString, ToCStr};
-use io;
 use mem;
 use os;
-use ptr;
-use io::process::{ProcessExit, ExitStatus, ExitSignal};
-use collections;
 use path::BytesContainer;
-use hash::Hash;
-use io::{IoResult, IoError};
-
+use ptr;
+use str;
+use sys::fs::FileDesc;
 use sys::fs;
 use sys::{self, retry, c, wouldblock, set_nonblocking, ms_to_timeval, timer};
-use sys::fs::FileDesc;
 use sys_common::helper_thread::Helper;
 use sys_common::{AsInner, mkerr_libc, timeout};
 
-use io::fs::PathExtensions;
-
 pub use sys_common::ProcessConfig;
 
 /// A value representing a child process.
@@ -142,10 +141,10 @@ impl Process {
                 // Split the value and test each path to see if the
                 // program exists.
                 for path in os::split_paths(v.container_as_bytes()).into_iter() {
-                    let path = path.join(cfg.program().as_bytes_no_nul())
+                    let path = path.join(cfg.program().as_bytes())
                                    .with_extension(os::consts::EXE_EXTENSION);
                     if path.exists() {
-                        return Some(path.to_c_str())
+                        return Some(CString::from_slice(path.as_vec()))
                     }
                 }
                 break
@@ -363,11 +362,11 @@ fn zeroed_process_information() -> libc::types::os::arch::extra::PROCESS_INFORMA
 
 fn make_command_line(prog: &CString, args: &[CString]) -> String {
     let mut cmd = String::new();
-    append_arg(&mut cmd, prog.as_str()
+    append_arg(&mut cmd, str::from_utf8(prog.as_bytes()).ok()
                              .expect("expected program name to be utf-8 encoded"));
     for arg in args.iter() {
         cmd.push(' ');
-        append_arg(&mut cmd, arg.as_str()
+        append_arg(&mut cmd, str::from_utf8(arg.as_bytes()).ok()
                                 .expect("expected argument to be utf-8 encoded"));
     }
     return cmd;
@@ -449,7 +448,7 @@ fn with_dirp<T, F>(d: Option<&CString>, cb: F) -> T where
 {
     match d {
       Some(dir) => {
-          let dir_str = dir.as_str()
+          let dir_str = str::from_utf8(dir.as_bytes()).ok()
                            .expect("expected workingdirectory to be utf-8 encoded");
           let mut dir_str: Vec<u16> = dir_str.utf16_units().collect();
           dir_str.push(0);