diff --git a/src/lib.rs b/src/lib.rs
index 57919c5..2593e3b 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -258,8 +258,10 @@
     if #[cfg(windows)] {
         mod windows;
         pub use windows::*;
-    } else {
+    } else if #[cfg(unix)] {
         mod unix;
         pub use unix::*;
+    } else {
+        // Unknown target_family
     }
 }
diff --git a/src/unix/bsd/apple/mod.rs b/src/unix/bsd/apple/mod.rs
index ec0fe7c..e96f433 100644
--- a/src/unix/bsd/apple/mod.rs
+++ b/src/unix/bsd/apple/mod.rs
@@ -946,6 +946,6 @@
         mod b64;
         pub use self::b64::*;
     } else {
-        // unknown arch...
+        // Unknown target_arch
     }
 }
diff --git a/src/unix/bsd/freebsdlike/freebsd/mod.rs b/src/unix/bsd/freebsdlike/freebsd/mod.rs
index 171889e..7d98ef4 100644
--- a/src/unix/bsd/freebsdlike/freebsd/mod.rs
+++ b/src/unix/bsd/freebsdlike/freebsd/mod.rs
@@ -86,6 +86,6 @@
         mod x86_64;
         pub use self::x86_64::*;
     } else {
-        // ...
+        // Unknown target_arch
     }
 }
diff --git a/src/unix/bsd/mod.rs b/src/unix/bsd/mod.rs
index 139edf7..b633003 100644
--- a/src/unix/bsd/mod.rs
+++ b/src/unix/bsd/mod.rs
@@ -350,6 +350,6 @@
         mod freebsdlike;
         pub use self::freebsdlike::*;
     } else {
-        // ...
+        // Unknown target_os
     }
 }
diff --git a/src/unix/bsd/openbsdlike/mod.rs b/src/unix/bsd/openbsdlike/mod.rs
index 1cd6eb8..1a2bdff 100644
--- a/src/unix/bsd/openbsdlike/mod.rs
+++ b/src/unix/bsd/openbsdlike/mod.rs
@@ -402,8 +402,10 @@
     } else if #[cfg(target_os = "netbsd")] {
         mod netbsd;
         pub use self::netbsd::*;
-    } else {
+    } else if #[cfg(target_os = "openbsd")] {
         mod openbsd;
         pub use self::openbsd::*;
+    } else {
+        // Unknown target_os
     }
 }
diff --git a/src/unix/mod.rs b/src/unix/mod.rs
index 3ffb3b7..77b24f2 100644
--- a/src/unix/mod.rs
+++ b/src/unix/mod.rs
@@ -733,6 +733,6 @@
         mod solaris;
         pub use self::solaris::*;
     } else {
-        // ...
+        // Unknown target_os
     }
 }
diff --git a/src/unix/notbsd/android/mod.rs b/src/unix/notbsd/android/mod.rs
index f039683..0a01bcc 100644
--- a/src/unix/notbsd/android/mod.rs
+++ b/src/unix/notbsd/android/mod.rs
@@ -657,6 +657,6 @@
         mod b64;
         pub use self::b64::*;
     } else {
-        // ...
+        // Unknown target_pointer_width
     }
 }
diff --git a/src/unix/notbsd/linux/musl/b32/mod.rs b/src/unix/notbsd/linux/musl/b32/mod.rs
index 668e8fc..ad74e88 100644
--- a/src/unix/notbsd/linux/musl/b32/mod.rs
+++ b/src/unix/notbsd/linux/musl/b32/mod.rs
@@ -38,5 +38,7 @@
     } else if #[cfg(any(target_arch = "asmjs"))] {
         mod asmjs;
         pub use self::asmjs::*;
-    } else { }
+    } else {
+        // Unknown target_arch
+    }
 }
diff --git a/src/unix/notbsd/linux/other/b32/mod.rs b/src/unix/notbsd/linux/other/b32/mod.rs
index 908fa40..b39ff68 100644
--- a/src/unix/notbsd/linux/other/b32/mod.rs
+++ b/src/unix/notbsd/linux/other/b32/mod.rs
@@ -90,6 +90,6 @@
         mod powerpc;
         pub use self::powerpc::*;
     } else {
-        // ...
+        // Unknown target_arch
     }
 }
diff --git a/src/unix/notbsd/linux/other/b64/mod.rs b/src/unix/notbsd/linux/other/b64/mod.rs
index 28d9e4d..663b093 100644
--- a/src/unix/notbsd/linux/other/b64/mod.rs
+++ b/src/unix/notbsd/linux/other/b64/mod.rs
@@ -25,8 +25,10 @@
     } else if #[cfg(any(target_arch = "powerpc64"))] {
         mod powerpc64;
         pub use self::powerpc64::*;
-    } else {
+    } else if #[cfg(any(target_arch = "x86_64"))] {
         mod x86_64;
         pub use self::x86_64::*;
+    } else {
+        // Unknown target_arch
     }
 }
diff --git a/src/unix/notbsd/linux/other/mod.rs b/src/unix/notbsd/linux/other/mod.rs
index 09d7e35..3ac57fe 100644
--- a/src/unix/notbsd/linux/other/mod.rs
+++ b/src/unix/notbsd/linux/other/mod.rs
@@ -491,6 +491,6 @@
         mod b64;
         pub use self::b64::*;
     } else {
-        // ...
+        // Unknown target_arch
     }
 }
diff --git a/src/unix/notbsd/mod.rs b/src/unix/notbsd/mod.rs
index 6106438..7cdd63c 100644
--- a/src/unix/notbsd/mod.rs
+++ b/src/unix/notbsd/mod.rs
@@ -133,6 +133,7 @@
     } else if #[cfg(target_pointer_width = "64")] {
         const ULONG_SIZE: usize = 64;
     } else {
+        // Unknown target_pointer_width
     }
 }
 
@@ -680,6 +681,6 @@
         mod android;
         pub use self::android::*;
     } else {
-        // ...
+        // Unknown target_os
     }
 }
diff --git a/src/windows.rs b/src/windows.rs
index 3f7f160..21b6e13 100644
--- a/src/windows.rs
+++ b/src/windows.rs
@@ -72,9 +72,11 @@
     if #[cfg(all(target_env = "gnu"))] {
         pub const L_tmpnam: ::c_uint = 14;
         pub const TMP_MAX: ::c_uint = 0x7fff;
-    } else {
+    } else if #[cfg(all(target_env = "msvc"))] {
         pub const L_tmpnam: ::c_uint = 260;
         pub const TMP_MAX: ::c_uint = 0x7fff_ffff;
+    } else {
+        // Unknown target_env
     }
 }