Use the nix crate.

Cargo.toml

@@ -17,5 +17,8 @@ rustc_version = "0.2.1"
 semver = "0.9.0"
 toml = "0.2.1"
 
+[target.'cfg(not(windows))'.dependencies]
+nix = "0.15"
+
 [target.'cfg(windows)'.dependencies]
 winapi = { version = "0.3.7", features = ["winbase"] }

src/docker.rs

@@ -116,7 +116,7 @@ pub fn run(target: &Target,
         .args(&["-e", "XARGO_HOME=/xargo"])
         .args(&["-e", "CARGO_HOME=/cargo"])
         .args(&["-e", "CARGO_TARGET_DIR=/target"])
-        .args(&["-e", &format!("USER={}", id::username())]);
+        .args(&["-e", &format!("USER={}", id::username().unwrap().unwrap())]);
 
     if let Ok(value) = env::var("QEMU_STRACE") {
         docker.args(&["-e", &format!("QEMU_STRACE={}", value)]);

src/id.rs

@@ -2,6 +2,8 @@
 use libc;
 #[cfg(not(target_os = "windows"))]
 use std::ffi::CStr;
+#[cfg(not(target_os = "windows"))]
+use nix::{errno::{errno, Errno}, unistd::{Gid, Uid}, Error};
 
 #[cfg(target_os = "windows")]
 pub fn group() -> u32 {
@@ -10,7 +12,7 @@ pub fn group() -> u32 {
 
 #[cfg(not(target_os = "windows"))]
 pub fn group() -> u32 {
-    unsafe { libc::getgid() }
+    Gid::current().as_raw()
 }
 
 #[cfg(target_os = "windows")]
@@ -20,7 +22,7 @@ pub fn user() -> u32 {
 
 #[cfg(not(target_os = "windows"))]
 pub fn user() -> u32 {
-    unsafe { libc::getuid() }
+    Uid::current().as_raw()
 }
 
 #[cfg(target_os = "windows")]
@@ -51,10 +53,22 @@ pub fn username() -> String {
 }
 
 #[cfg(not(target_os = "windows"))]
-pub fn username() -> String {
-    unsafe {
-        CStr::from_ptr((*libc::getpwuid(user())).pw_name)
-            .to_string_lossy()
-            .into_owned()
-    }
+pub fn username() -> Result<Option<String>, Error>  {
+    let name = unsafe {
+        Errno::clear();
+
+        let passwd = libc::getpwuid(Uid::current().as_raw());
+
+        if passwd.is_null() {
+            let errno = errno();
+
+            if errno == 0 { return Ok(None) }
+
+            return Err(Error::Sys(Errno::from_i32(errno)))
+        }
+
+        CStr::from_ptr((*passwd).pw_name)
+    };
+
+    Ok(Some(name.to_string_lossy().into_owned()))
 }

src/main.rs

@@ -8,6 +8,7 @@ extern crate libc;
 extern crate rustc_version;
 extern crate semver;
 extern crate toml;
+extern crate nix;
 
 #[cfg(target_os = "windows")]
 extern crate winapi;