From 929c3e50fafecc920891d9b94a8913c5c175f88b Mon Sep 17 00:00:00 2001
From: Christopher Vella <cvella@microsoft.com>
Date: Mon, 26 May 2025 13:30:21 +1000
Subject: [PATCH 1/5] Allow pinning of windows modules

---
 src/os/windows/mod.rs | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/src/os/windows/mod.rs b/src/os/windows/mod.rs
index 1cbc57be3..deacabf43 100644
--- a/src/os/windows/mod.rs
+++ b/src/os/windows/mod.rs
@@ -171,6 +171,36 @@ impl Library {
         ret
     }
 
+    /// Attempts to pin the module represented by the current `Library` into memory.
+    /// If successful, the module will remain in memory regardless of the refcount for this `Library`
+    pub fn pin(&self) -> Result<(), crate::Error> {
+        const GET_MODULE_HANDLE_EX_FLAG_PIN: u32 = 0x1;
+        const GET_MODULE_HANDLE_EX_FLAG_FROM_ADDRESS: u32 = 0x4;
+        let ret = unsafe {
+            let mut handle: HMODULE = 0;
+            with_get_last_error(
+                |source| crate::Error::GetModuleHandleExW { source },
+                || {
+                    // Make sure no winapi calls as a result of drop happen inside this closure, because
+                    // otherwise that might change the return value of the GetLastError.
+                    let result = GetModuleHandleExW(
+                        GET_MODULE_HANDLE_EX_FLAG_PIN | GET_MODULE_HANDLE_EX_FLAG_FROM_ADDRESS,
+                        self.0 as *const u16,
+                        &mut handle,
+                    );
+                    if result == 0 {
+                        None
+                    } else {
+                        Some(())
+                    }
+                },
+            )
+            .map_err(|e| e.unwrap_or(crate::Error::GetModuleHandleExWUnknown))
+        };
+
+        ret
+    }
+
     /// Get a pointer to a function or static variable by symbol name.
     ///
     /// The `symbol` may not contain any null bytes, with the exception of the last byte. A null

From d83bc9e35e02496e5d64d5b67555de2e080e0fb1 Mon Sep 17 00:00:00 2001
From: Christopher Vella <cvella@microsoft.com>
Date: Mon, 26 May 2025 13:39:47 +1000
Subject: [PATCH 2/5] Add test for module pinning on windows

---
 tests/functions.rs | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/tests/functions.rs b/tests/functions.rs
index c94592e7a..84d5267d9 100644
--- a/tests/functions.rs
+++ b/tests/functions.rs
@@ -279,6 +279,17 @@ fn works_getlasterror0() {
     }
 }
 
+#[cfg(windows)]
+#[test]
+fn works_pin_module() {
+    use libloading::os::windows::Library;
+
+    unsafe {
+        let lib = Library::new("kernel32.dll").unwrap();
+        lib.pin().unwrap();
+    }
+}
+
 #[cfg(windows)]
 #[test]
 fn library_open_already_loaded() {

From 3e2d21d36f70ea87dbe9b8df0a1b44f5305d9229 Mon Sep 17 00:00:00 2001
From: Christopher Vella <cvella@microsoft.com>
Date: Mon, 26 May 2025 13:44:27 +1000
Subject: [PATCH 3/5] Comment update

---
 src/os/windows/mod.rs | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/os/windows/mod.rs b/src/os/windows/mod.rs
index deacabf43..f13b611dd 100644
--- a/src/os/windows/mod.rs
+++ b/src/os/windows/mod.rs
@@ -183,6 +183,10 @@ impl Library {
                 || {
                     // Make sure no winapi calls as a result of drop happen inside this closure, because
                     // otherwise that might change the return value of the GetLastError.
+
+                    // We use our cached module handle of this `Library` instead of the module name. This works
+                    // if we also pass the flag `GET_MODULE_HANDLE_EX_FLAG_FROM_ADDRESS` because on Windows, module handles
+                    // are the loaded base address of the module.
                     let result = GetModuleHandleExW(
                         GET_MODULE_HANDLE_EX_FLAG_PIN | GET_MODULE_HANDLE_EX_FLAG_FROM_ADDRESS,
                         self.0 as *const u16,

From 24c9d70f47ef05aa800b1e919bc76565a0d74582 Mon Sep 17 00:00:00 2001
From: Christopher Vella <cvella@microsoft.com>
Date: Tue, 27 May 2025 07:46:05 +1000
Subject: [PATCH 4/5] Comment update

---
 src/os/windows/mod.rs | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/src/os/windows/mod.rs b/src/os/windows/mod.rs
index f13b611dd..07ee5c846 100644
--- a/src/os/windows/mod.rs
+++ b/src/os/windows/mod.rs
@@ -172,6 +172,12 @@ impl Library {
     }
 
     /// Attempts to pin the module represented by the current `Library` into memory.
+    /// 
+    /// Calls `GetModuleHandleExW` with the flag `GET_MODULE_HANDLE_EX_FLAG_PIN` to pin the module.
+    /// See the [MSDN documentation][msdn] for more information.
+    /// 
+    /// [msdn]: https://learn.microsoft.com/en-us/windows/win32/api/libloaderapi/nf-libloaderapi-getmodulehandleexw
+    /// 
     /// If successful, the module will remain in memory regardless of the refcount for this `Library`
     pub fn pin(&self) -> Result<(), crate::Error> {
         const GET_MODULE_HANDLE_EX_FLAG_PIN: u32 = 0x1;

From 7585067cf62999ebe0dd724dcb7e09b067a6a937 Mon Sep 17 00:00:00 2001
From: Christopher Vella <cvella@microsoft.com>
Date: Tue, 27 May 2025 08:00:50 +1000
Subject: [PATCH 5/5] cargo clippy

---
 src/os/windows/mod.rs | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/src/os/windows/mod.rs b/src/os/windows/mod.rs
index 07ee5c846..59fa69a5e 100644
--- a/src/os/windows/mod.rs
+++ b/src/os/windows/mod.rs
@@ -182,7 +182,7 @@ impl Library {
     pub fn pin(&self) -> Result<(), crate::Error> {
         const GET_MODULE_HANDLE_EX_FLAG_PIN: u32 = 0x1;
         const GET_MODULE_HANDLE_EX_FLAG_FROM_ADDRESS: u32 = 0x4;
-        let ret = unsafe {
+        unsafe {
             let mut handle: HMODULE = 0;
             with_get_last_error(
                 |source| crate::Error::GetModuleHandleExW { source },
@@ -206,9 +206,7 @@ impl Library {
                 },
             )
             .map_err(|e| e.unwrap_or(crate::Error::GetModuleHandleExWUnknown))
-        };
-
-        ret
+        }
     }
 
     /// Get a pointer to a function or static variable by symbol name.