use a 'safe-wrappers' feature to gate the FamStructWrappers

The FamStructWrappers definitions as well as the vmm-sys-util
dependency are now gated by an opt-in `safe-wrappers` feature.

Signed-off-by: Adrian Catangiu <acatan@amazon.com>

Author: acatangiu

Cargo.toml

@@ -9,8 +9,10 @@ keywords = ["kvm"]
 license = "Apache-2.0"
 
 [features]
+default = []
 kvm-v4_14_0 = []
 kvm-v4_20_0 = []
+safe-wrappers = ["vmm-sys-util"]
 
 [dependencies]
-vmm-sys-util = ">=0.2.0"
+vmm-sys-util = { version = ">=0.2.0", optional = true }

src/lib.rs

@@ -6,7 +6,10 @@
 #![allow(non_snake_case)]
 
 #[macro_use]
-#[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
+#[cfg(all(
+    feature = "safe-wrappers",
+    any(target_arch = "x86", target_arch = "x86_64")
+))]
 extern crate vmm_sys_util;
 
 #[cfg(any(target_arch = "x86", target_arch = "x86_64"))]

src/x86/mod.rs

@@ -1,6 +1,7 @@
 // Copyright 2019 Amazon.com, Inc. or its affiliates. All Rights Reserved.
 // SPDX-License-Identifier: Apache-2.0
 
+#[cfg(feature = "safe-wrappers")]
 mod fam_wrappers;
 
 #[cfg(feature = "kvm-v4_14_0")]
@@ -24,5 +25,6 @@ pub mod bindings {
     #[cfg(all(not(feature = "kvm-v4_14_0"), not(feature = "kvm-v4_20_0")))]
     pub use super::bindings_v4_20_0::*;
 
+    #[cfg(feature = "safe-wrappers")]
     pub use super::fam_wrappers::*;
 }