Process::new etc should support non-utf8 commands/args

The existing APIs for spawning processes took strings for the command
and arguments, but the underlying system may not impose utf8 encoding,
so this is overly limiting.

The assumption we actually want to make is just that the command and
arguments are viewable as [u8] slices with no interior NULLs, i.e., as
CStrings. The ToCStr trait is a handy bound for types that meet this
requirement (such as &str and Path).

However, since the commands and arguments are often a mixture of
strings and paths, it would be inconvenient to take a slice with a
single T: ToCStr bound. So this patch revamps the process creation API
to instead use a builder-style interface, called `Command`, allowing
arguments to be added one at a time with differing ToCStr
implementations for each.

The initial cut of the builder API has some drawbacks that can be
addressed once issue #13851 (libstd as a facade) is closed. These are
detailed as FIXMEs.

Closes #11650.

[breaking-change]

1 files changed, 2 insertions, 5 deletions

diff --git a/src/libworkcache/lib.rs b/src/libworkcache/lib.rs
index c2dd8459540..98fbb00f437 100644
--- a/src/libworkcache/lib.rs
+++ b/src/libworkcache/lib.rs
@@ -488,7 +488,7 @@ impl<'a, T:Send +
 #[cfg(not(target_os="android"))] // FIXME(#10455)
 fn test() {
     use std::os;
-    use std::io::{fs, Process};
+    use std::io::{fs, Command};
     use std::str::from_utf8;
 
     // Create a path to a new file 'filename' in the directory in which
@@ -522,10 +522,7 @@ fn test() {
         prep.exec(proc(_exe) {
             let out = make_path("foo.o".to_strbuf());
             let compiler = if cfg!(windows) {"gcc"} else {"cc"};
-            // FIXME (#9639): This needs to handle non-utf8 paths
-            Process::status(compiler, [pth.as_str().unwrap().to_owned(),
-                                    "-o".to_owned(),
-                                    out.as_str().unwrap().to_owned()]).unwrap();
+            Command::new(compiler).arg(pth).arg("-o").arg(out.clone()).status().unwrap();
 
             let _proof_of_concept = subcx.prep("subfn");
             // Could run sub-rules inside here.