Proper return values from XS, and code should work

lib/Sys/Linux/Mount.xs

@@ -12,11 +12,7 @@ PROTOTYPES: ENABLE
  # XS comments begin with " #" to avoid them being interpreted as pre-processor
  # directives
  
-int _mount_sys(source, target, filesystem, mountflags, data)
+SV *_mount_sys(const char *source, const char *target, const char *filesystem, unsigned long mountflags, const char *data)
-const char *source
-const char *target
-const char *filesystem
-unsigned long mountflags
-const char *data
 	CODE:
-	RETVAL = mount(source, target, filesystem, mountflags, (const void *) data);
+	ST(0) = sv_newmortal();
+	sv_setiv(ST(0), mount(source, target, filesystem, mountflags, (const void *) data));

lib/Sys/Linux/Unshare.xs

@@ -15,9 +15,8 @@ PROTOTYPES: ENABLE
  # XS comments begin with " #" to avoid them being interpreted as pre-processor
  # directives
  
-int 
+SV * _unshare_sys(int flags)
-_unshare_sys(flags)
-int flags
 	CODE:
-	RETVAL = unshare(flags);
+	ST(0) = sv_newmortal();
+	sv_setiv(ST(0), unshare(flags));
 

t/02-namespace.t

@@ -0,0 +1,13 @@
+use Test::More tests => 3;
+
+# test 1
+use_ok("Sys::Linux::Namespace", 'namespace');
+
+# test 2
+SKIP: {
+  skip "Need to be root to run test", 2 unless $< == 0;
+  ok(namespace({private_tmp => 1}), "Setup private /tmp");
+  
+  # tmp is empty
+  is_deeply([glob "/tmp/*"], [], "/tmp is empty afterwards"); 
+}