COM scope fix.

As stated on the MSDN, A thread must call CoUninitialize once for each
successful call it has made to the CoInitialize or CoInitializeEx
function, including any call that returns S_FALSE. We were not calling
it previously, so the fix is to make a scope guard, which handles this.

Author: den-mentiei

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name        = "thound"
-version     = "0.1.0"
+version     = "0.1.1"
 authors     = ["Denys Mentiei <endden@gmail.com>"]
 description = "Finds the folders with VC toolchain and Windows SDK"
 license     = "MIT"

README.md

@@ -23,7 +23,7 @@ Add `thound` to your `Cargo.toml`:
 
 ``` toml
 [dependencies]
-thound = "0.1.0"
+thound = "0.1"
 ```
 
 ## Usage

src/lib.rs

@@ -123,11 +123,7 @@ pub fn find_vc_and_windows_sdk() -> Option<Info> {
 }
 
 fn find_vc_toolchain() -> Option<ToolchainInfo> {
-	let hr = unsafe { CoInitializeEx(null_mut(), COINIT_MULTITHREADED) };
-	// S_FALSE means COM has been already initialized.
-	if hr != S_OK && hr != S_FALSE {
-		return None;
-	}
+	let _com = ComScope::start()?;
 
 	let mut config = null_mut();
 	let status = unsafe {

src/winapi.rs

@@ -107,6 +107,7 @@ extern "stdcall" {
 #[link(name = "Ole32")]
 extern "stdcall" {
 	pub fn CoInitializeEx(pvReserved: LPVOID, dwCoInit: DWORD) -> HRESULT;
+	pub fn CoUninitialize();
 	pub fn CoCreateInstance(
 		rclsid: REFCLSID,
 		pUnkOuter: LPUNKNOWN,
@@ -400,3 +401,29 @@ pub(crate) fn reg_query_string_value(key: &RegKey, sub_key: &str) -> Option<Path
 	let root = OsString::from_wide(&value[..]);
 	Some(root.into())
 }
+
+// COM initialization seems to be a ref-count of some kind under the
+// hood, so we need to make sure we play by the rules and uninit it.
+pub(crate) struct ComScope;
+
+impl ComScope {
+	#[must_use]
+	pub fn start() -> Option<Self> {
+		let hr = unsafe { CoInitializeEx(null_mut(), COINIT_MULTITHREADED) };
+		// S_FALSE means COM has been already initialized.
+		if hr != S_OK && hr != S_FALSE {
+			return None;
+		}
+
+		Some(ComScope)
+	}
+}
+
+impl Drop for ComScope {
+	fn drop(&mut self) {
+		// A thread must call CoUninitialize once for each successful
+		// call it has made to the CoInitialize or CoInitializeEx
+		// function, including any call that returns S_FALSE.
+		unsafe { CoUninitialize() };
+	}
+}