Fix running on Windows

Add directory where asan DLL is to path when running.

Cargo.toml

@@ -21,6 +21,9 @@ toml = "0.5.9"
 rustc_version = "0.4.0"
 cargo_metadata = "0.18.1"
 
+[target.'cfg(target_env = "msvc")'.dependencies]
+cc = "1.1"
+
 [dev-dependencies]
 assert_cmd = "2.0.7"
 predicates = "2.1.4"

src/project.rs

@@ -454,6 +454,17 @@ impl FuzzProject {
             cmd.arg(format!("-fork={}", run.jobs));
         }
 
+        #[cfg(target_env = "msvc")]
+        {
+            use crate::utils::{append_to_pathvar, get_asan_path};
+            // On Windows asan is in a DLL. This DLL is not on PATH by default, so the recommended
+            // action is to add the directory to PATH when running.
+            let asan = get_asan_path().with_context(|| "could not find AddressSanitizer DLL")?;
+            let new_path =
+                append_to_pathvar(asan).with_context(|| "could not get PATH variable")?;
+            cmd.env("PATH", new_path);
+        }
+
         // When libfuzzer finds failing inputs, those inputs will end up in the
         // artifacts directory. To easily filter old artifacts from new ones,
         // get the current time, and then later we only consider files modified

src/utils.rs

@@ -1,4 +1,32 @@
+use std::ffi::OsString;
+
 /// The default target to pass to cargo, to workaround issue #11.
 pub fn default_target() -> &'static str {
     current_platform::CURRENT_PLATFORM
 }
+
+/// Gets the path to the asan DLL required for the asan instrumented binary to run.
+#[cfg(target_env = "msvc")]
+pub fn get_asan_path() -> Option<std::path::PathBuf> {
+    // The asan DLL sits next to cl & link.exe. So grab the parent path.
+    Some(
+        cc::windows_registry::find_tool(default_target(), "link.exe")?
+            .path()
+            .parent()?
+            .to_owned(),
+    )
+}
+
+/// Append a value to the PATH variable
+#[cfg(target_env = "msvc")]
+pub fn append_to_pathvar(path: std::path::PathBuf) -> Option<OsString> {
+    use std::env;
+
+    if let Some(current) = env::var_os("PATH") {
+        let mut current = env::split_paths(&current).collect::<Vec<_>>();
+        current.push(path);
+        return env::join_paths(current).ok();
+    }
+
+    return None;
+}