extern arithmetic

build.rs

@@ -6,7 +6,7 @@ fn main() {
         builder.compiler("clang");
     }
 
-    builder.flag("-O3").flag("-flto=thin");
+    builder.flag("-flto=thin");
 
     build_ll(builder.clone());
     build_c(builder);
@@ -21,13 +21,32 @@ fn build_ll(mut builder: cc::Build) {
 }
 
 fn build_c(mut builder: cc::Build) {
-    builder
-        .file("src/math/math.c")
-        .flag("-ffinite-math-only")
-        .flag("-fassociative-math")
-        .flag("-freciprocal-math")
-        .flag("-fno-signed-zeros")
-        .flag("-fno-trapping-math")
-        .flag("-ffp-contract=fast")
-        .compile("math")
+    builder.flag("-O3");
+
+    #[cfg(feature = "finite-math-only")]
+    builder.flag("-ffinite-math-only");
+
+    #[cfg(feature = "associative-math")]
+    builder.flag("-fassociative-math");
+
+    #[cfg(feature = "reciprocal-math")]
+    builder.flag("-freciprocal-math");
+
+    #[cfg(feature = "no-signed-zeros")]
+    builder.flag("-fno-signed-zeros");
+
+    #[cfg(feature = "no-trapping-math")]
+    builder.flag("-fno-trapping-math");
+
+    #[cfg(feature = "fp-contract-fast")]
+    builder.flag("-ffp-contract=fast");
+
+    // TODO figure out if this works
+    //#[cfg(feature = "approx-func")]
+    //builder.flag("-Xclang -fapprox-func");
+
+    #[cfg(feature = "denormal-fp-math-preserve-sign")]
+    builder.flag("-fdenormal-fp-math=preserve-sign");
+
+    builder.file("src/math/math.c").compile("math")
 }