diff --git a/Cargo.toml b/Cargo.toml
index 33d5c06b..50fbbe7d 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -83,3 +83,13 @@ panic = 'abort'
 
 [profile.dev]
 panic = 'abort'
+
+[lints.rust]
+# Values used during testing
+unexpected_cfgs = { level = "warn", check-cfg = [
+  'cfg(feature, values("arch"))',
+  'cfg(feature, values("force-soft-floats"))',
+  'cfg(feature, values("unstable-float"))',
+  'cfg(feature, values("unstable-intrinsics"))',
+  'cfg(feature, values("unstable-test-support"))',
+] }
diff --git a/build.rs b/build.rs
index 22ec9e4d..238d9179 100644
--- a/build.rs
+++ b/build.rs
@@ -1,6 +1,8 @@
 use std::{collections::BTreeMap, env, path::PathBuf, sync::atomic::Ordering};
 
 mod configure;
+#[path = "libm/configure.rs"]
+mod libm_configure;
 
 use configure::{configure_f16_f128, Target};
 
@@ -14,12 +16,9 @@ fn main() {
     configure_check_cfg();
     configure_f16_f128(&target);
 
-    println!("cargo:compiler-rt={}", cwd.join("compiler-rt").display());
+    configure_libm();
 
-    // Activate libm's unstable features to make full use of Nightly.
-    println!("cargo::rustc-check-cfg=cfg(feature, values(\"unstable\", \"force-soft-floats\"))");
-    println!("cargo:rustc-cfg=feature=\"unstable\"");
-    println!("cargo:rustc-cfg=feature=\"force-soft-floats\"");
+    println!("cargo:compiler-rt={}", cwd.join("compiler-rt").display());
 
     // Emscripten's runtime includes all the builtins
     if target.os == "emscripten" {
@@ -104,6 +103,18 @@ fn main() {
     }
 }
 
+/// Run configuration for `libm` since it is included directly.
+fn configure_libm() {
+    let cfg = libm_configure::Config::from_env();
+    libm_configure::emit_libm_config(&cfg);
+
+    // Activate libm's unstable features to make full use of Nightly.
+    println!("cargo:rustc-cfg=feature=\"force-soft-floats\"");
+    println!("cargo:rustc-cfg=feature=\"unstable-float\"");
+    println!("cargo:rustc-cfg=feature=\"unstable-intrinsics\"");
+    println!("cargo:rustc-cfg=feature=\"unstable\"");
+}
+
 fn aarch64_symbol(ordering: Ordering) -> &'static str {
     match ordering {
         Ordering::Relaxed => "relax",
diff --git a/libm b/libm
index f4e5b38a..9d043c56 160000
--- a/libm
+++ b/libm
@@ -1 +1 @@
-Subproject commit f4e5b38aee0e0c592a82ed45b21cd068c9b6c89a
+Subproject commit 9d043c563e213661e87ff87a746bd98f39e81b7a
diff --git a/src/math.rs b/src/math.rs
index 477dfe36..da208239 100644
--- a/src/math.rs
+++ b/src/math.rs
@@ -1,3 +1,4 @@
+#[rustfmt::skip]
 #[allow(dead_code)]
 #[allow(unused_imports)]
 #[allow(clippy::all)]