sequester build and link into a separate function

Author: addisoncrump

Cargo.toml

@@ -16,8 +16,8 @@ once_cell = "1"
 cc = { version = "1.0", features = ["parallel"] }
 
 [features]
-default = ["link"]
-link = []
+default = ["link_libfuzzer"]
+link_libfuzzer = []
 arbitrary-derive = ["arbitrary/derive"]
 
 [workspace]

build.rs

@@ -1,42 +1,46 @@
-fn main() {
-    if cfg!(feature = "link") {
-        println!("cargo:rerun-if-env-changed=CUSTOM_LIBFUZZER_PATH");
-        if let Ok(custom) = ::std::env::var("CUSTOM_LIBFUZZER_PATH") {
-            println!("cargo:rerun-if-changed={custom}");
+fn build_and_link_libfuzzer() {
+    println!("cargo:rerun-if-env-changed=CUSTOM_LIBFUZZER_PATH");
+    if let Ok(custom) = ::std::env::var("CUSTOM_LIBFUZZER_PATH") {
+        println!("cargo:rerun-if-changed={custom}");
 
-            let custom_lib_path = ::std::path::PathBuf::from(&custom);
-            let custom_lib_dir = custom_lib_path.parent().unwrap().to_string_lossy();
+        let custom_lib_path = ::std::path::PathBuf::from(&custom);
+        let custom_lib_dir = custom_lib_path.parent().unwrap().to_string_lossy();
 
-            let custom_lib_name = custom_lib_path.file_stem().unwrap().to_string_lossy();
-            let custom_lib_name = custom_lib_name
-                .strip_prefix("lib")
-                .unwrap_or(custom_lib_name.as_ref());
+        let custom_lib_name = custom_lib_path.file_stem().unwrap().to_string_lossy();
+        let custom_lib_name = custom_lib_name
+            .strip_prefix("lib")
+            .unwrap_or(custom_lib_name.as_ref());
 
-            println!("cargo:rustc-link-search=native={}", custom_lib_dir);
-            println!("cargo:rustc-link-lib=static={}", custom_lib_name);
+        println!("cargo:rustc-link-search=native={}", custom_lib_dir);
+        println!("cargo:rustc-link-lib=static={}", custom_lib_name);
 
-            match std::env::var("CUSTOM_LIBFUZZER_STD_CXX") {
-                // Default behavior for backwards compat.
-                Err(_) => println!("cargo:rustc-link-lib=stdc++"),
-                Ok(s) if s == "none" => (),
-                Ok(s) => println!("cargo:rustc-link-lib={}", s),
-            }
-        } else {
-            let mut build = cc::Build::new();
-            let sources = ::std::fs::read_dir("libfuzzer")
-                .expect("listable source directory")
-                .map(|de| de.expect("file in directory").path())
-                .filter(|p| p.extension().map(|ext| ext == "cpp") == Some(true))
-                .collect::<Vec<_>>();
-            for source in sources.iter() {
-                println!("cargo:rerun-if-changed={}", source.display());
-                build.file(source.to_str().unwrap());
-            }
-            build.flag("-std=c++17");
-            build.flag("-fno-omit-frame-pointer");
-            build.flag("-w");
-            build.cpp(true);
-            build.compile("libfuzzer.a");
+        match std::env::var("CUSTOM_LIBFUZZER_STD_CXX") {
+            // Default behavior for backwards compat.
+            Err(_) => println!("cargo:rustc-link-lib=stdc++"),
+            Ok(s) if s == "none" => (),
+            Ok(s) => println!("cargo:rustc-link-lib={}", s),
+        }
+    } else {
+        let mut build = cc::Build::new();
+        let sources = ::std::fs::read_dir("libfuzzer")
+            .expect("listable source directory")
+            .map(|de| de.expect("file in directory").path())
+            .filter(|p| p.extension().map(|ext| ext == "cpp") == Some(true))
+            .collect::<Vec<_>>();
+        for source in sources.iter() {
+            println!("cargo:rerun-if-changed={}", source.display());
+            build.file(source.to_str().unwrap());
         }
+        build.flag("-std=c++17");
+        build.flag("-fno-omit-frame-pointer");
+        build.flag("-w");
+        build.cpp(true);
+        build.compile("libfuzzer.a");
+    }
+}
+
+fn main() {
+    if cfg!(feature = "link_libfuzzer") {
+        build_and_link_libfuzzer();
     }
 }