Use libc::getpid instead of std::process::id

Until the std::process::id interface becomes stable.

.travis.yml

@@ -1,8 +1,8 @@
 language: rust
 cache: cargo
 rust:
+  - stable
   - nightly
-  # - stable # would fail, std::process::id is unstable
 
 matrix:
   allow_failures:

Cargo.toml

@@ -19,6 +19,7 @@ serde_derive = "^1.0"
 serde_json   = "^1.0"
 byte         = "0.2"
 log          = "~0.4"
+libc         = "0.2.39" # until std::process::id is stable
 
 [dependencies.uuid]
 version  = "^0.6.2"

src/lib.rs

@@ -1,5 +1,3 @@
-#![feature(getpid)]
-
 #[macro_use]
 extern crate log;
 #[macro_use]
@@ -8,6 +6,7 @@ extern crate serde;
 extern crate serde_json;
 extern crate byte;
 extern crate uuid;
+extern crate libc;
 
 #[macro_use]
 mod macros;

src/models/set_activity.rs

@@ -1,4 +1,4 @@
-use std::process::id as pid;
+use libc::getpid;
 use models::Command;
 
 #[derive(Debug, Default, Serialize)]
@@ -10,7 +10,7 @@ pub struct SetActivityArgs {
 impl SetActivityArgs {
     pub fn command(args: SetActivity) -> Command<Self> {
         Command::new("SET_ACTIVITY", Self {
-            pid: pid(),
+            pid: unsafe { getpid() as u32 },
             activity: args
         })
     }