Update unix.rs

Author: ChrisDenton

library/std/src/sys/process/unix/unix.rs

@@ -378,6 +378,7 @@ impl Command {
             callback()?;
         }
 
+        let mut _reset = None;
         if let Some(envp) = maybe_envp
             && self.get_resolve_in_parent_path()
             && self.env_saw_path()
@@ -390,8 +391,9 @@ impl Command {
                 program: &CStr,
                 args: &CStringArray,
                 envp: &CStringArray,
-            ) -> libc::c_int {
-                unsafe { libc::execvpe(program.as_ptr(), args.as_ptr(), envp.as_ptr()) }
+            ) -> io::Error {
+                unsafe { libc::execvpe(program.as_ptr(), args.as_ptr(), envp.as_ptr()) };
+                io::Error::last_os_error()
             }
 
             // ...so if we're not gnu then use our own implementation.
@@ -400,7 +402,7 @@ impl Command {
                 program: &CStr,
                 args: &CStringArray,
                 envp: &CStringArray,
-            ) -> libc::c_int {
+            ) -> io::Error {
                 unsafe {
                     let name = program.to_bytes();
                     let mut buffer =
@@ -433,18 +435,18 @@ impl Command {
                         }
                         environ = environ.add(1);
                     }
-                    // If execve is successful then it'll never return, thus we'll never reach this point.
-                    -1
+                    // If execve is successful then it'll never return,
+                    // thus we only reach this point on failure..
+                    io::Error::from_raw_os_error(libc::ENOENT)
                 }
             }
-            exec_with_env(self.get_program_cstr(), self.get_argv(), envp);
+            return Err(exec_with_env(self.get_program_cstr(), self.get_argv(), envp));
         } else if let Some(envp) = maybe_envp {
             // Although we're performing an exec here we may also return with an
             // error from this function (without actually exec'ing) in which case we
             // want to be sure to restore the global environment back to what it
             // once was, ensuring that our temporary override, when free'd, doesn't
             // corrupt our process's environment.
-            let mut _reset = None;
             struct Reset(*const *const libc::c_char);
 
             impl Drop for Reset {
@@ -457,8 +459,8 @@ impl Command {
 
             _reset = Some(Reset(*sys::env::environ()));
             *sys::env::environ() = envp.as_ptr();
-            libc::execvp(self.get_program_cstr().as_ptr(), self.get_argv().as_ptr());
         }
+        libc::execvp(self.get_program_cstr().as_ptr(), self.get_argv().as_ptr());
         Err(io::Error::last_os_error())
     }