diff --git a/Cargo.toml b/Cargo.toml
index dfd1fde..48f6ee0 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -3,5 +3,11 @@ authors = ["Jorge Aparicio <japaricious@gmail.com>"]
 name = "rustc_builtins"
 version = "0.1.0"
 
+[dependencies]
+rlibc = { git = "https://github.com/alexcrichton/rlibc", optional = true }
+
 [dev-dependencies]
 quickcheck = "0.3.1"
+
+[features]
+default = ["rlibc/weak"]
diff --git a/src/lib.rs b/src/lib.rs
index 2d1c839..7b621dd 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -18,12 +18,13 @@ extern crate quickcheck;
 #[cfg(test)]
 extern crate core;
 
+#[cfg(all(not(windows), not(target_os = "macos")))]
+extern crate rlibc;
+
 #[cfg(target_arch = "arm")]
 pub mod arm;
 
 pub mod udiv;
-#[cfg(all(not(windows), not(target_os = "macos")))]
-pub mod mem;
 pub mod mul;
 pub mod shift;
 
diff --git a/src/mem.rs b/src/mem.rs
deleted file mode 100644
index 7a94034..0000000
--- a/src/mem.rs
+++ /dev/null
@@ -1,60 +0,0 @@
-// NOTE Copied verbatim from the rlibc crate
-// cf. https://crates.io/crates/rlibc
-
-#[linkage = "weak"]
-#[no_mangle]
-pub unsafe extern "C" fn memcpy(dest: *mut u8, src: *const u8, n: usize) -> *mut u8 {
-    let mut i = 0;
-    while i < n {
-        *dest.offset(i as isize) = *src.offset(i as isize);
-        i += 1;
-    }
-    dest
-}
-
-#[linkage = "weak"]
-#[no_mangle]
-pub unsafe extern "C" fn memmove(dest: *mut u8, src: *const u8, n: usize) -> *mut u8 {
-    if src < dest as *const u8 {
-        // copy from end
-        let mut i = n;
-        while i != 0 {
-            i -= 1;
-            *dest.offset(i as isize) = *src.offset(i as isize);
-        }
-    } else {
-        // copy from beginning
-        let mut i = 0;
-        while i < n {
-            *dest.offset(i as isize) = *src.offset(i as isize);
-            i += 1;
-        }
-    }
-    dest
-}
-
-#[linkage = "weak"]
-#[no_mangle]
-pub unsafe extern "C" fn memset(s: *mut u8, c: i32, n: usize) -> *mut u8 {
-    let mut i = 0;
-    while i < n {
-        *s.offset(i as isize) = c as u8;
-        i += 1;
-    }
-    s
-}
-
-#[linkage = "weak"]
-#[no_mangle]
-pub unsafe extern "C" fn memcmp(s1: *const u8, s2: *const u8, n: usize) -> i32 {
-    let mut i = 0;
-    while i < n {
-        let a = *s1.offset(i as isize);
-        let b = *s2.offset(i as isize);
-        if a != b {
-            return a as i32 - b as i32;
-        }
-        i += 1;
-    }
-    0
-}