Windows/WinCE: Improve the run-time dynamic linking scheme

Prior to this commit, the Windows and WinCE backends had a specific
shortcoming when loading DLLs, that being that once loaded they were
never unloaded. This commit improves this by providing a means to
unload the DLLs during cleanup.

Note that the use of GetModuleHandle() has been removed in favor of
the exclusive use of LoadLibrary(). This was done to ensure that a
reference count is taken against the loaded DLL, which guards against
some other part of the application unloading the DLL that libusb
is currently using.

Signed-off-by: Chris Dickens <christopher.a.dickens@gmail.com>

7 files changed, 246 insertions, 160 deletions

diff --git a/libusb/os/wince_usb.c b/libusb/os/wince_usb.c
index 96cad67..fc95e9c 100644
--- a/libusb/os/wince_usb.c
+++ b/libusb/os/wince_usb.c
@@ -109,33 +109,40 @@ static int translate_driver_error(DWORD error)
 	}
 }
 
-static int init_dllimports()
-{
-	DLL_LOAD(ceusbkwrapper.dll, UkwOpenDriver, TRUE);
-	DLL_LOAD(ceusbkwrapper.dll, UkwGetDeviceList, TRUE);
-	DLL_LOAD(ceusbkwrapper.dll, UkwReleaseDeviceList, TRUE);
-	DLL_LOAD(ceusbkwrapper.dll, UkwGetDeviceAddress, TRUE);
-	DLL_LOAD(ceusbkwrapper.dll, UkwGetDeviceDescriptor, TRUE);
-	DLL_LOAD(ceusbkwrapper.dll, UkwGetConfigDescriptor, TRUE);
-	DLL_LOAD(ceusbkwrapper.dll, UkwCloseDriver, TRUE);
-	DLL_LOAD(ceusbkwrapper.dll, UkwCancelTransfer, TRUE);
-	DLL_LOAD(ceusbkwrapper.dll, UkwIssueControlTransfer, TRUE);
-	DLL_LOAD(ceusbkwrapper.dll, UkwClaimInterface, TRUE);
-	DLL_LOAD(ceusbkwrapper.dll, UkwReleaseInterface, TRUE);
-	DLL_LOAD(ceusbkwrapper.dll, UkwSetInterfaceAlternateSetting, TRUE);
-	DLL_LOAD(ceusbkwrapper.dll, UkwClearHaltHost, TRUE);
-	DLL_LOAD(ceusbkwrapper.dll, UkwClearHaltDevice, TRUE);
-	DLL_LOAD(ceusbkwrapper.dll, UkwGetConfig, TRUE);
-	DLL_LOAD(ceusbkwrapper.dll, UkwSetConfig, TRUE);
-	DLL_LOAD(ceusbkwrapper.dll, UkwResetDevice, TRUE);
-	DLL_LOAD(ceusbkwrapper.dll, UkwKernelDriverActive, TRUE);
-	DLL_LOAD(ceusbkwrapper.dll, UkwAttachKernelDriver, TRUE);
-	DLL_LOAD(ceusbkwrapper.dll, UkwDetachKernelDriver, TRUE);
-	DLL_LOAD(ceusbkwrapper.dll, UkwIssueBulkTransfer, TRUE);
-	DLL_LOAD(ceusbkwrapper.dll, UkwIsPipeHalted, TRUE);
+static int init_dllimports(void)
+{
+	DLL_GET_HANDLE(ceusbkwrapper);
+	DLL_LOAD_FUNC(ceusbkwrapper, UkwOpenDriver, TRUE);
+	DLL_LOAD_FUNC(ceusbkwrapper, UkwGetDeviceList, TRUE);
+	DLL_LOAD_FUNC(ceusbkwrapper, UkwReleaseDeviceList, TRUE);
+	DLL_LOAD_FUNC(ceusbkwrapper, UkwGetDeviceAddress, TRUE);
+	DLL_LOAD_FUNC(ceusbkwrapper, UkwGetDeviceDescriptor, TRUE);
+	DLL_LOAD_FUNC(ceusbkwrapper, UkwGetConfigDescriptor, TRUE);
+	DLL_LOAD_FUNC(ceusbkwrapper, UkwCloseDriver, TRUE);
+	DLL_LOAD_FUNC(ceusbkwrapper, UkwCancelTransfer, TRUE);
+	DLL_LOAD_FUNC(ceusbkwrapper, UkwIssueControlTransfer, TRUE);
+	DLL_LOAD_FUNC(ceusbkwrapper, UkwClaimInterface, TRUE);
+	DLL_LOAD_FUNC(ceusbkwrapper, UkwReleaseInterface, TRUE);
+	DLL_LOAD_FUNC(ceusbkwrapper, UkwSetInterfaceAlternateSetting, TRUE);
+	DLL_LOAD_FUNC(ceusbkwrapper, UkwClearHaltHost, TRUE);
+	DLL_LOAD_FUNC(ceusbkwrapper, UkwClearHaltDevice, TRUE);
+	DLL_LOAD_FUNC(ceusbkwrapper, UkwGetConfig, TRUE);
+	DLL_LOAD_FUNC(ceusbkwrapper, UkwSetConfig, TRUE);
+	DLL_LOAD_FUNC(ceusbkwrapper, UkwResetDevice, TRUE);
+	DLL_LOAD_FUNC(ceusbkwrapper, UkwKernelDriverActive, TRUE);
+	DLL_LOAD_FUNC(ceusbkwrapper, UkwAttachKernelDriver, TRUE);
+	DLL_LOAD_FUNC(ceusbkwrapper, UkwDetachKernelDriver, TRUE);
+	DLL_LOAD_FUNC(ceusbkwrapper, UkwIssueBulkTransfer, TRUE);
+	DLL_LOAD_FUNC(ceusbkwrapper, UkwIsPipeHalted, TRUE);
+
 	return LIBUSB_SUCCESS;
 }
 
+static void exit_dllimports(void)
+{
+	DLL_FREE_HANDLE(ceusbkwrapper);
+}
+
 static int init_device(
 	struct libusb_device *dev, UKW_DEVICE drv_dev,
 	unsigned char bus_addr, unsigned char dev_addr)
@@ -215,6 +222,9 @@ static int wince_init(struct libusb_context *ctx)
 
 init_exit: // Holds semaphore here.
 	if (!concurrent_usage && r != LIBUSB_SUCCESS) { // First init failed?
+		exit_dllimports();
+		exit_polling();
+
 		if (driver_handle != INVALID_HANDLE_VALUE) {
 			UkwCloseDriver(driver_handle);
 			driver_handle = INVALID_HANDLE_VALUE;
@@ -248,6 +258,7 @@ static void wince_exit(void)
 
 	// Only works if exits and inits are balanced exactly
 	if (--concurrent_usage < 0) {	// Last exit
+		exit_dllimports();
 		exit_polling();
 
 		if (driver_handle != INVALID_HANDLE_VALUE) {
diff --git a/libusb/os/wince_usb.h b/libusb/os/wince_usb.h
index b3403db..edcb9fc 100644
--- a/libusb/os/wince_usb.h
+++ b/libusb/os/wince_usb.h
@@ -87,28 +87,29 @@ typedef struct {
  * to specify the currently active configuration for the device. */
 #define UKW_ACTIVE_CONFIGURATION -1
 
-DLL_DECLARE(WINAPI, HANDLE, UkwOpenDriver, ());
-DLL_DECLARE(WINAPI, BOOL, UkwGetDeviceList, (HANDLE, LPUKW_DEVICE, DWORD, LPDWORD));
-DLL_DECLARE(WINAPI, void, UkwReleaseDeviceList, (HANDLE, LPUKW_DEVICE, DWORD));
-DLL_DECLARE(WINAPI, BOOL, UkwGetDeviceAddress, (UKW_DEVICE, unsigned char*, unsigned char*, unsigned long*));
-DLL_DECLARE(WINAPI, BOOL, UkwGetDeviceDescriptor, (UKW_DEVICE, LPUKW_DEVICE_DESCRIPTOR));
-DLL_DECLARE(WINAPI, BOOL, UkwGetConfigDescriptor, (UKW_DEVICE, DWORD, LPVOID, DWORD, LPDWORD));
-DLL_DECLARE(WINAPI, void, UkwCloseDriver, (HANDLE));
-DLL_DECLARE(WINAPI, BOOL, UkwCancelTransfer, (UKW_DEVICE, LPOVERLAPPED, DWORD));
-DLL_DECLARE(WINAPI, BOOL, UkwIssueControlTransfer, (UKW_DEVICE, DWORD, LPUKW_CONTROL_HEADER, LPVOID, DWORD, LPDWORD, LPOVERLAPPED));
-DLL_DECLARE(WINAPI, BOOL, UkwClaimInterface, (UKW_DEVICE, DWORD));
-DLL_DECLARE(WINAPI, BOOL, UkwReleaseInterface, (UKW_DEVICE, DWORD));
-DLL_DECLARE(WINAPI, BOOL, UkwSetInterfaceAlternateSetting, (UKW_DEVICE, DWORD, DWORD));
-DLL_DECLARE(WINAPI, BOOL, UkwClearHaltHost, (UKW_DEVICE, UCHAR));
-DLL_DECLARE(WINAPI, BOOL, UkwClearHaltDevice, (UKW_DEVICE, UCHAR));
-DLL_DECLARE(WINAPI, BOOL, UkwGetConfig, (UKW_DEVICE, PUCHAR));
-DLL_DECLARE(WINAPI, BOOL, UkwSetConfig, (UKW_DEVICE, UCHAR));
-DLL_DECLARE(WINAPI, BOOL, UkwResetDevice, (UKW_DEVICE));
-DLL_DECLARE(WINAPI, BOOL, UkwKernelDriverActive, (UKW_DEVICE, DWORD, PBOOL));
-DLL_DECLARE(WINAPI, BOOL, UkwAttachKernelDriver, (UKW_DEVICE, DWORD));
-DLL_DECLARE(WINAPI, BOOL, UkwDetachKernelDriver, (UKW_DEVICE, DWORD));
-DLL_DECLARE(WINAPI, BOOL, UkwIssueBulkTransfer, (UKW_DEVICE, DWORD, UCHAR, LPVOID, DWORD, LPDWORD, LPOVERLAPPED));
-DLL_DECLARE(WINAPI, BOOL, UkwIsPipeHalted, (UKW_DEVICE, UCHAR, LPBOOL));
+DLL_DECLARE_HANDLE(ceusbkwrapper);
+DLL_DECLARE_FUNC(WINAPI, HANDLE, UkwOpenDriver, ());
+DLL_DECLARE_FUNC(WINAPI, BOOL, UkwGetDeviceList, (HANDLE, LPUKW_DEVICE, DWORD, LPDWORD));
+DLL_DECLARE_FUNC(WINAPI, void, UkwReleaseDeviceList, (HANDLE, LPUKW_DEVICE, DWORD));
+DLL_DECLARE_FUNC(WINAPI, BOOL, UkwGetDeviceAddress, (UKW_DEVICE, unsigned char*, unsigned char*, unsigned long*));
+DLL_DECLARE_FUNC(WINAPI, BOOL, UkwGetDeviceDescriptor, (UKW_DEVICE, LPUKW_DEVICE_DESCRIPTOR));
+DLL_DECLARE_FUNC(WINAPI, BOOL, UkwGetConfigDescriptor, (UKW_DEVICE, DWORD, LPVOID, DWORD, LPDWORD));
+DLL_DECLARE_FUNC(WINAPI, void, UkwCloseDriver, (HANDLE));
+DLL_DECLARE_FUNC(WINAPI, BOOL, UkwCancelTransfer, (UKW_DEVICE, LPOVERLAPPED, DWORD));
+DLL_DECLARE_FUNC(WINAPI, BOOL, UkwIssueControlTransfer, (UKW_DEVICE, DWORD, LPUKW_CONTROL_HEADER, LPVOID, DWORD, LPDWORD, LPOVERLAPPED));
+DLL_DECLARE_FUNC(WINAPI, BOOL, UkwClaimInterface, (UKW_DEVICE, DWORD));
+DLL_DECLARE_FUNC(WINAPI, BOOL, UkwReleaseInterface, (UKW_DEVICE, DWORD));
+DLL_DECLARE_FUNC(WINAPI, BOOL, UkwSetInterfaceAlternateSetting, (UKW_DEVICE, DWORD, DWORD));
+DLL_DECLARE_FUNC(WINAPI, BOOL, UkwClearHaltHost, (UKW_DEVICE, UCHAR));
+DLL_DECLARE_FUNC(WINAPI, BOOL, UkwClearHaltDevice, (UKW_DEVICE, UCHAR));
+DLL_DECLARE_FUNC(WINAPI, BOOL, UkwGetConfig, (UKW_DEVICE, PUCHAR));
+DLL_DECLARE_FUNC(WINAPI, BOOL, UkwSetConfig, (UKW_DEVICE, UCHAR));
+DLL_DECLARE_FUNC(WINAPI, BOOL, UkwResetDevice, (UKW_DEVICE));
+DLL_DECLARE_FUNC(WINAPI, BOOL, UkwKernelDriverActive, (UKW_DEVICE, DWORD, PBOOL));
+DLL_DECLARE_FUNC(WINAPI, BOOL, UkwAttachKernelDriver, (UKW_DEVICE, DWORD));
+DLL_DECLARE_FUNC(WINAPI, BOOL, UkwDetachKernelDriver, (UKW_DEVICE, DWORD));
+DLL_DECLARE_FUNC(WINAPI, BOOL, UkwIssueBulkTransfer, (UKW_DEVICE, DWORD, UCHAR, LPVOID, DWORD, LPDWORD, LPOVERLAPPED));
+DLL_DECLARE_FUNC(WINAPI, BOOL, UkwIsPipeHalted, (UKW_DEVICE, UCHAR, LPBOOL));
 
 // Used to determine if an endpoint status really is halted on a failed transfer.
 #define STATUS_HALT_FLAG 0x1
diff --git a/libusb/os/windows_common.h b/libusb/os/windows_common.h
index 45c59af..0149e11 100644
--- a/libusb/os/windows_common.h
+++ b/libusb/os/windows_common.h
@@ -62,45 +62,70 @@
 
 
 /*
- * API macros - from libusb-win32 1.x
+ * API macros - leveraged from libusb-win32 1.x
  */
-#define DLL_DECLARE_PREFIXNAME(api, ret, prefixname, name, args)    \
-	typedef ret (api * __dll_##name##_t)args;                       \
-	static __dll_##name##_t prefixname = NULL
-
 #ifndef _WIN32_WCE
-#define DLL_STRINGIFY(dll) #dll
-#define DLL_GET_MODULE_HANDLE(dll) GetModuleHandleA(DLL_STRINGIFY(dll))
-#define DLL_LOAD_LIBRARY(dll) LoadLibraryA(DLL_STRINGIFY(dll))
+#define DLL_STRINGIFY(s) #s
+#define DLL_LOAD_LIBRARY(name) LoadLibraryA(DLL_STRINGIFY(name))
 #else
-#define DLL_STRINGIFY(dll) L#dll
-#define DLL_GET_MODULE_HANDLE(dll) GetModuleHandle(DLL_STRINGIFY(dll))
-#define DLL_LOAD_LIBRARY(dll) LoadLibrary(DLL_STRINGIFY(dll))
+#define DLL_STRINGIFY(s) L#s
+#define DLL_LOAD_LIBRARY(name) LoadLibrary(DLL_STRINGIFY(name))
 #endif
 
-#define DLL_LOAD_PREFIXNAME(dll, prefixname, name, ret_on_failure) \
-	do {                                                           \
-		HMODULE h = DLL_GET_MODULE_HANDLE(dll);                    \
-	if (!h)                                                        \
-		h = DLL_LOAD_LIBRARY(dll);                                 \
-	if (!h) {                                                      \
-		if (ret_on_failure) { return LIBUSB_ERROR_NOT_FOUND; }     \
-		else { break; }                                            \
-	}                                                              \
-	prefixname = (__dll_##name##_t)GetProcAddress(h,               \
-	                        DLL_STRINGIFY(name));                  \
-	if (prefixname) break;                                         \
-	prefixname = (__dll_##name##_t)GetProcAddress(h,               \
-	                        DLL_STRINGIFY(name) DLL_STRINGIFY(A)); \
-	if (prefixname) break;                                         \
-	prefixname = (__dll_##name##_t)GetProcAddress(h,               \
-	                        DLL_STRINGIFY(name) DLL_STRINGIFY(W)); \
-	if (prefixname) break;                                         \
-	if(ret_on_failure)                                             \
-		return LIBUSB_ERROR_NOT_FOUND;                             \
+/*
+ * Macros for handling DLL themselves
+ */
+#define DLL_DECLARE_HANDLE(name)				\
+	static HMODULE __dll_##name##_handle = NULL
+
+#define DLL_GET_HANDLE(name)					\
+	do {							\
+		__dll_##name##_handle = DLL_LOAD_LIBRARY(name);	\
+		if (!__dll_##name##_handle)			\
+			return LIBUSB_ERROR_OTHER;		\
+	} while (0)
+
+#define DLL_FREE_HANDLE(name)					\
+	do {							\
+		if (__dll_##name##_handle) {			\
+			FreeLibrary(__dll_##name##_handle);	\
+			__dll_##name##_handle = NULL;		\
+		}						\
+	} while(0)
+
+
+/*
+ * Macros for handling functions within a DLL
+ */
+#define DLL_DECLARE_FUNC_PREFIXNAME(api, ret, prefixname, name, args)	\
+	typedef ret (api * __dll_##name##_func_t)args;			\
+	static __dll_##name##_func_t prefixname = NULL
+
+#define DLL_DECLARE_FUNC(api, ret, name, args)				\
+	DLL_DECLARE_FUNC_PREFIXNAME(api, ret, name, name, args)
+#define DLL_DECLARE_FUNC_PREFIXED(api, ret, prefix, name, args)		\
+	DLL_DECLARE_FUNC_PREFIXNAME(api, ret, prefix##name, name, args)
+
+#define DLL_LOAD_FUNC_PREFIXNAME(dll, prefixname, name, ret_on_failure)	\
+	do {								\
+		HMODULE h = __dll_##dll##_handle;			\
+		prefixname = (__dll_##name##_func_t)GetProcAddress(h,	\
+				DLL_STRINGIFY(name));			\
+		if (prefixname)						\
+			break;						\
+		prefixname = (__dll_##name##_func_t)GetProcAddress(h,	\
+				DLL_STRINGIFY(name) DLL_STRINGIFY(A));	\
+		if (prefixname)						\
+			break;						\
+		prefixname = (__dll_##name##_func_t)GetProcAddress(h,	\
+				DLL_STRINGIFY(name) DLL_STRINGIFY(W));	\
+		if (prefixname)						\
+			break;						\
+		if (ret_on_failure)					\
+			return LIBUSB_ERROR_NOT_FOUND;			\
 	} while(0)
 
-#define DLL_DECLARE(api, ret, name, args)   DLL_DECLARE_PREFIXNAME(api, ret, name, name, args)
-#define DLL_LOAD(dll, name, ret_on_failure) DLL_LOAD_PREFIXNAME(dll, name, name, ret_on_failure)
-#define DLL_DECLARE_PREFIXED(api, ret, prefix, name, args)   DLL_DECLARE_PREFIXNAME(api, ret, prefix##name, name, args)
-#define DLL_LOAD_PREFIXED(dll, prefix, name, ret_on_failure) DLL_LOAD_PREFIXNAME(dll, prefix##name, name, ret_on_failure)
+#define DLL_LOAD_FUNC(dll, name, ret_on_failure)			\
+	DLL_LOAD_FUNC_PREFIXNAME(dll, name, name, ret_on_failure)
+#define DLL_LOAD_FUNC_PREFIXED(dll, prefix, name, ret_on_failure)	\
+	DLL_LOAD_FUNC_PREFIXNAME(dll, prefix##name, name, ret_on_failure)
diff --git a/libusb/os/windows_nt_common.c b/libusb/os/windows_nt_common.c
index 55b6818..650e2fa 100644
--- a/libusb/os/windows_nt_common.c
+++ b/libusb/os/windows_nt_common.c
@@ -54,9 +54,10 @@ static HANDLE timer_thread = NULL;
 static DWORD timer_thread_id = 0;
 
 /* User32 dependencies */
-DLL_DECLARE_PREFIXED(WINAPI, BOOL, p, GetMessageA, (LPMSG, HWND, UINT, UINT));
-DLL_DECLARE_PREFIXED(WINAPI, BOOL, p, PeekMessageA, (LPMSG, HWND, UINT, UINT, UINT));
-DLL_DECLARE_PREFIXED(WINAPI, BOOL, p, PostThreadMessageA, (DWORD, UINT, WPARAM, LPARAM));
+DLL_DECLARE_HANDLE(User32);
+DLL_DECLARE_FUNC_PREFIXED(WINAPI, BOOL, p, GetMessageA, (LPMSG, HWND, UINT, UINT));
+DLL_DECLARE_FUNC_PREFIXED(WINAPI, BOOL, p, PeekMessageA, (LPMSG, HWND, UINT, UINT, UINT));
+DLL_DECLARE_FUNC_PREFIXED(WINAPI, BOOL, p, PostThreadMessageA, (DWORD, UINT, WPARAM, LPARAM));
 
 static unsigned __stdcall windows_clock_gettime_threaded(void *param);
 
@@ -282,13 +283,19 @@ unsigned long htab_hash(const char *str)
 
 static int windows_init_dlls(void)
 {
-	DLL_LOAD_PREFIXED(User32.dll, p, GetMessageA, TRUE);
-	DLL_LOAD_PREFIXED(User32.dll, p, PeekMessageA, TRUE);
-	DLL_LOAD_PREFIXED(User32.dll, p, PostThreadMessageA, TRUE);
+	DLL_GET_HANDLE(User32);
+	DLL_LOAD_FUNC_PREFIXED(User32, p, GetMessageA, TRUE);
+	DLL_LOAD_FUNC_PREFIXED(User32, p, PeekMessageA, TRUE);
+	DLL_LOAD_FUNC_PREFIXED(User32, p, PostThreadMessageA, TRUE);
 
 	return LIBUSB_SUCCESS;
 }
 
+static void windows_exit_dlls(void)
+{
+	DLL_FREE_HANDLE(User32);
+}
+
 static bool windows_init_clock(struct libusb_context *ctx)
 {
 	DWORD_PTR affinity, dummy;
@@ -601,4 +608,5 @@ void windows_common_exit(void)
 {
 	htab_destroy();
 	windows_destroy_clock();
+	windows_exit_dlls();
 }
diff --git a/libusb/os/windows_winusb.c b/libusb/os/windows_winusb.c
index 5bf35a2..f790736 100644
--- a/libusb/os/windows_winusb.c
+++ b/libusb/os/windows_winusb.c
@@ -124,8 +124,10 @@ static usbi_mutex_t autoclaim_lock;
 			return LIBUSB_ERROR_ACCESS;	\
 	} while(0)
 
+static HMODULE WinUSBX_handle = NULL;
 static struct winusb_interface WinUSBX[SUB_API_MAX];
 static const char *sub_api_name[SUB_API_MAX] = WINUSBX_DRV_NAMES;
+
 static bool api_hid_available = false;
 #define CHECK_HID_AVAILABLE				\
 	do {						\
@@ -207,25 +209,45 @@ static char *sanitize_path(const char *path)
  */
 static int init_dlls(void)
 {
-	DLL_LOAD(Cfgmgr32.dll, CM_Get_Parent, TRUE);
-	DLL_LOAD(Cfgmgr32.dll, CM_Get_Child, TRUE);
-	DLL_LOAD(Cfgmgr32.dll, CM_Get_Sibling, TRUE);
-	DLL_LOAD(Cfgmgr32.dll, CM_Get_Device_IDA, TRUE);
+	DLL_GET_HANDLE(Cfgmgr32);
+	DLL_LOAD_FUNC(Cfgmgr32, CM_Get_Parent, TRUE);
+	DLL_LOAD_FUNC(Cfgmgr32, CM_Get_Child, TRUE);
+	DLL_LOAD_FUNC(Cfgmgr32, CM_Get_Sibling, TRUE);
+	DLL_LOAD_FUNC(Cfgmgr32, CM_Get_Device_IDA, TRUE);
+
 	// Prefixed to avoid conflict with header files
-	DLL_LOAD_PREFIXED(OLE32.dll, p, CLSIDFromString, TRUE);
-	DLL_LOAD_PREFIXED(SetupAPI.dll, p, SetupDiGetClassDevsA, TRUE);
-	DLL_LOAD_PREFIXED(SetupAPI.dll, p, SetupDiEnumDeviceInfo, TRUE);
-	DLL_LOAD_PREFIXED(SetupAPI.dll, p, SetupDiEnumDeviceInterfaces, TRUE);
-	DLL_LOAD_PREFIXED(SetupAPI.dll, p, SetupDiGetDeviceInterfaceDetailA, TRUE);
-	DLL_LOAD_PREFIXED(SetupAPI.dll, p, SetupDiDestroyDeviceInfoList, TRUE);
-	DLL_LOAD_PREFIXED(SetupAPI.dll, p, SetupDiOpenDevRegKey, TRUE);
-	DLL_LOAD_PREFIXED(SetupAPI.dll, p, SetupDiGetDeviceRegistryPropertyA, TRUE);
-	DLL_LOAD_PREFIXED(SetupAPI.dll, p, SetupDiOpenDeviceInterfaceRegKey, TRUE);
-	DLL_LOAD_PREFIXED(AdvAPI32.dll, p, RegQueryValueExW, TRUE);
-	DLL_LOAD_PREFIXED(AdvAPI32.dll, p, RegCloseKey, TRUE);
+	DLL_GET_HANDLE(AdvAPI32);
+	DLL_LOAD_FUNC_PREFIXED(AdvAPI32, p, RegQueryValueExW, TRUE);
+	DLL_LOAD_FUNC_PREFIXED(AdvAPI32, p, RegCloseKey, TRUE);
+
+	DLL_GET_HANDLE(Kernel32);
+	DLL_LOAD_FUNC_PREFIXED(Kernel32, p, IsWow64Process, FALSE);
+
+	DLL_GET_HANDLE(OLE32);
+	DLL_LOAD_FUNC_PREFIXED(OLE32, p, CLSIDFromString, TRUE);
+
+	DLL_GET_HANDLE(SetupAPI);
+	DLL_LOAD_FUNC_PREFIXED(SetupAPI, p, SetupDiGetClassDevsA, TRUE);
+	DLL_LOAD_FUNC_PREFIXED(SetupAPI, p, SetupDiEnumDeviceInfo, TRUE);
+	DLL_LOAD_FUNC_PREFIXED(SetupAPI, p, SetupDiEnumDeviceInterfaces, TRUE);
+	DLL_LOAD_FUNC_PREFIXED(SetupAPI, p, SetupDiGetDeviceInterfaceDetailA, TRUE);
+	DLL_LOAD_FUNC_PREFIXED(SetupAPI, p, SetupDiDestroyDeviceInfoList, TRUE);
+	DLL_LOAD_FUNC_PREFIXED(SetupAPI, p, SetupDiOpenDevRegKey, TRUE);
+	DLL_LOAD_FUNC_PREFIXED(SetupAPI, p, SetupDiGetDeviceRegistryPropertyA, TRUE);
+	DLL_LOAD_FUNC_PREFIXED(SetupAPI, p, SetupDiOpenDeviceInterfaceRegKey, TRUE);
+
 	return LIBUSB_SUCCESS;
 }
 
+static void exit_dlls(void)
+{
+	DLL_FREE_HANDLE(Cfgmgr32);
+	DLL_FREE_HANDLE(AdvAPI32);
+	DLL_FREE_HANDLE(Kernel32);
+	DLL_FREE_HANDLE(OLE32);
+	DLL_FREE_HANDLE(SetupAPI);
+}
+
 /*
  * enumerate interfaces for the whole USB class
  *
@@ -647,9 +669,8 @@ static BOOL is_x64(void)
 
 	// Detect if we're running a 32 or 64 bit system
 	if (sizeof(uintptr_t) < 8) {
-		DLL_LOAD_PREFIXED(Kernel32.dll, p, IsWow64Process, FALSE);
 		if (pIsWow64Process != NULL)
-			(*pIsWow64Process)(GetCurrentProcess(), &ret);
+			pIsWow64Process(GetCurrentProcess(), &ret);
 	} else {
 		ret = TRUE;
 	}
@@ -816,6 +837,7 @@ init_exit: // Holds semaphore here.
 	if (!concurrent_usage && r != LIBUSB_SUCCESS) { // First init failed?
 		for (i = 0; i < USB_API_MAX; i++)
 			usb_api_backend[i].exit(SUBAPI_NOT_SET);
+		exit_dlls();
 		exit_polling();
 		windows_common_exit();
 		usbi_mutex_destroy(&autoclaim_lock);
@@ -1644,6 +1666,7 @@ static void windows_exit(void)
 	if (--concurrent_usage < 0) { // Last exit
 		for (i = 0; i < USB_API_MAX; i++)
 			usb_api_backend[i].exit(SUB_API_NOTSET);
+		exit_dlls();
 		exit_polling();
 		windows_common_exit();
 		usbi_mutex_destroy(&autoclaim_lock);
@@ -2241,7 +2264,7 @@ const struct windows_usb_api_backend usb_api_backend[USB_API_MAX] = {
 #define WinUSBX_Set(fn)										\
 	do {											\
 		if (native_winusb)								\
-			WinUSBX[i].fn = (WinUsb_##fn##_t) GetProcAddress(h, "WinUsb_" #fn);	\
+			WinUSBX[i].fn = (WinUsb_##fn##_t)GetProcAddress(h, "WinUsb_" #fn);	\
 		else										\
 			pLibK_GetProcAddress((PVOID *)&WinUSBX[i].fn, i, KUSB_FNID_##fn);	\
 	} while (0)
@@ -2255,15 +2278,11 @@ static int winusbx_init(int sub_api, struct libusb_context *ctx)
 	LibK_GetProcAddress_t pLibK_GetProcAddress = NULL;
 	LibK_GetVersion_t pLibK_GetVersion;
 
-	h = GetModuleHandleA("libusbK");
-	if (h == NULL)
-		h = LoadLibraryA("libusbK");
+	h = LoadLibraryA("libusbK");
 
 	if (h == NULL) {
 		usbi_info(ctx, "libusbK DLL is not available, will use native WinUSB");
-		h = GetModuleHandleA("WinUSB");
-		if (h == NULL)
-			h = LoadLibraryA("WinUSB");
+		h = LoadLibraryA("WinUSB");
 
 		if (h == NULL) {
 			usbi_warn(ctx, "WinUSB DLL is not available either, "
@@ -2281,6 +2300,7 @@ static int winusbx_init(int sub_api, struct libusb_context *ctx)
 		pLibK_GetProcAddress = (LibK_GetProcAddress_t)GetProcAddress(h, "LibK_GetProcAddress");
 		if (pLibK_GetProcAddress == NULL) {
 			usbi_err(ctx, "LibK_GetProcAddress() not found in libusbK DLL");
+			FreeLibrary(h);
 			return LIBUSB_ERROR_NOT_FOUND;
 		}
 	}
@@ -2319,11 +2339,20 @@ static int winusbx_init(int sub_api, struct libusb_context *ctx)
 		}
 	}
 
+	WinUSBX_handle = h;
 	return LIBUSB_SUCCESS;
 }
 
 static int winusbx_exit(int sub_api)
 {
+	if (WinUSBX_handle != NULL) {
+		FreeLibrary(WinUSBX_handle);
+		WinUSBX_handle = NULL;
+
+		/* Reset the WinUSBX API structures */
+		memset(&WinUSBX, 0, sizeof(WinUSBX));
+	}
+
 	return LIBUSB_SUCCESS;
 }
 
@@ -3368,22 +3397,23 @@ static int _hid_class_request(struct hid_device_priv *dev, HANDLE hid_handle, in
  */
 static int hid_init(int sub_api, struct libusb_context *ctx)
 {
-	DLL_LOAD(hid.dll, HidD_GetAttributes, TRUE);
-	DLL_LOAD(hid.dll, HidD_GetHidGuid, TRUE);
-	DLL_LOAD(hid.dll, HidD_GetPreparsedData, TRUE);
-	DLL_LOAD(hid.dll, HidD_FreePreparsedData, TRUE);
-	DLL_LOAD(hid.dll, HidD_GetManufacturerString, TRUE);
-	DLL_LOAD(hid.dll, HidD_GetProductString, TRUE);
-	DLL_LOAD(hid.dll, HidD_GetSerialNumberString, TRUE);
-	DLL_LOAD(hid.dll, HidP_GetCaps, TRUE);
-	DLL_LOAD(hid.dll, HidD_SetNumInputBuffers, TRUE);
-	DLL_LOAD(hid.dll, HidD_SetFeature, TRUE);
-	DLL_LOAD(hid.dll, HidD_GetFeature, TRUE);
-	DLL_LOAD(hid.dll, HidD_GetPhysicalDescriptor, TRUE);
-	DLL_LOAD(hid.dll, HidD_GetInputReport, FALSE);
-	DLL_LOAD(hid.dll, HidD_SetOutputReport, FALSE);
-	DLL_LOAD(hid.dll, HidD_FlushQueue, TRUE);
-	DLL_LOAD(hid.dll, HidP_GetValueCaps, TRUE);
+	DLL_GET_HANDLE(hid);
+	DLL_LOAD_FUNC(hid, HidD_GetAttributes, TRUE);
+	DLL_LOAD_FUNC(hid, HidD_GetHidGuid, TRUE);
+	DLL_LOAD_FUNC(hid, HidD_GetPreparsedData, TRUE);
+	DLL_LOAD_FUNC(hid, HidD_FreePreparsedData, TRUE);
+	DLL_LOAD_FUNC(hid, HidD_GetManufacturerString, TRUE);
+	DLL_LOAD_FUNC(hid, HidD_GetProductString, TRUE);
+	DLL_LOAD_FUNC(hid, HidD_GetSerialNumberString, TRUE);
+	DLL_LOAD_FUNC(hid, HidP_GetCaps, TRUE);
+	DLL_LOAD_FUNC(hid, HidD_SetNumInputBuffers, TRUE);
+	DLL_LOAD_FUNC(hid, HidD_SetFeature, TRUE);
+	DLL_LOAD_FUNC(hid, HidD_GetFeature, TRUE);
+	DLL_LOAD_FUNC(hid, HidD_GetPhysicalDescriptor, TRUE);
+	DLL_LOAD_FUNC(hid, HidD_GetInputReport, FALSE);
+	DLL_LOAD_FUNC(hid, HidD_SetOutputReport, FALSE);
+	DLL_LOAD_FUNC(hid, HidD_FlushQueue, TRUE);
+	DLL_LOAD_FUNC(hid, HidP_GetValueCaps, TRUE);
 
 	api_hid_available = true;
 	return LIBUSB_SUCCESS;
@@ -3391,6 +3421,8 @@ static int hid_init(int sub_api, struct libusb_context *ctx)
 
 static int hid_exit(int sub_api)
 {
+	DLL_FREE_HANDLE(hid);
+
 	return LIBUSB_SUCCESS;
 }
 
diff --git a/libusb/os/windows_winusb.h b/libusb/os/windows_winusb.h
index 8f53c4a..047f2e2 100644
--- a/libusb/os/windows_winusb.h
+++ b/libusb/os/windows_winusb.h
@@ -314,25 +314,32 @@ struct driver_lookup {
 };
 
 /* OLE32 dependency */
-DLL_DECLARE_PREFIXED(WINAPI, HRESULT, p, CLSIDFromString, (LPCOLESTR, LPCLSID));
+DLL_DECLARE_HANDLE(OLE32);
+DLL_DECLARE_FUNC_PREFIXED(WINAPI, HRESULT, p, CLSIDFromString, (LPCOLESTR, LPCLSID));
 
+/* Kernel32 dependencies */
+DLL_DECLARE_HANDLE(Kernel32);
 /* This call is only available from XP SP2 */
-DLL_DECLARE_PREFIXED(WINAPI, BOOL, p, IsWow64Process, (HANDLE, PBOOL));
+DLL_DECLARE_FUNC_PREFIXED(WINAPI, BOOL, p, IsWow64Process, (HANDLE, PBOOL));
 
 /* SetupAPI dependencies */
-DLL_DECLARE_PREFIXED(WINAPI, HDEVINFO, p, SetupDiGetClassDevsA, (const GUID*, PCSTR, HWND, DWORD));
-DLL_DECLARE_PREFIXED(WINAPI, BOOL, p, SetupDiEnumDeviceInfo, (HDEVINFO, DWORD, PSP_DEVINFO_DATA));
-DLL_DECLARE_PREFIXED(WINAPI, BOOL, p, SetupDiEnumDeviceInterfaces, (HDEVINFO, PSP_DEVINFO_DATA,
+DLL_DECLARE_HANDLE(SetupAPI);
+DLL_DECLARE_FUNC_PREFIXED(WINAPI, HDEVINFO, p, SetupDiGetClassDevsA, (const GUID*, PCSTR, HWND, DWORD));
+DLL_DECLARE_FUNC_PREFIXED(WINAPI, BOOL, p, SetupDiEnumDeviceInfo, (HDEVINFO, DWORD, PSP_DEVINFO_DATA));
+DLL_DECLARE_FUNC_PREFIXED(WINAPI, BOOL, p, SetupDiEnumDeviceInterfaces, (HDEVINFO, PSP_DEVINFO_DATA,
 			const GUID*, DWORD, PSP_DEVICE_INTERFACE_DATA));
-DLL_DECLARE_PREFIXED(WINAPI, BOOL, p, SetupDiGetDeviceInterfaceDetailA, (HDEVINFO, PSP_DEVICE_INTERFACE_DATA,
+DLL_DECLARE_FUNC_PREFIXED(WINAPI, BOOL, p, SetupDiGetDeviceInterfaceDetailA, (HDEVINFO, PSP_DEVICE_INTERFACE_DATA,
 			PSP_DEVICE_INTERFACE_DETAIL_DATA_A, DWORD, PDWORD, PSP_DEVINFO_DATA));
-DLL_DECLARE_PREFIXED(WINAPI, BOOL, p, SetupDiDestroyDeviceInfoList, (HDEVINFO));
-DLL_DECLARE_PREFIXED(WINAPI, HKEY, p, SetupDiOpenDevRegKey, (HDEVINFO, PSP_DEVINFO_DATA, DWORD, DWORD, DWORD, REGSAM));
-DLL_DECLARE_PREFIXED(WINAPI, BOOL, p, SetupDiGetDeviceRegistryPropertyA, (HDEVINFO,
+DLL_DECLARE_FUNC_PREFIXED(WINAPI, BOOL, p, SetupDiDestroyDeviceInfoList, (HDEVINFO));
+DLL_DECLARE_FUNC_PREFIXED(WINAPI, HKEY, p, SetupDiOpenDevRegKey, (HDEVINFO, PSP_DEVINFO_DATA, DWORD, DWORD, DWORD, REGSAM));
+DLL_DECLARE_FUNC_PREFIXED(WINAPI, BOOL, p, SetupDiGetDeviceRegistryPropertyA, (HDEVINFO,
 			PSP_DEVINFO_DATA, DWORD, PDWORD, PBYTE, DWORD, PDWORD));
-DLL_DECLARE_PREFIXED(WINAPI, HKEY, p, SetupDiOpenDeviceInterfaceRegKey, (HDEVINFO, PSP_DEVICE_INTERFACE_DATA, DWORD, DWORD));
-DLL_DECLARE_PREFIXED(WINAPI, LONG, p, RegQueryValueExW, (HKEY, LPCWSTR, LPDWORD, LPDWORD, LPBYTE, LPDWORD));
-DLL_DECLARE_PREFIXED(WINAPI, LONG, p, RegCloseKey, (HKEY));
+DLL_DECLARE_FUNC_PREFIXED(WINAPI, HKEY, p, SetupDiOpenDeviceInterfaceRegKey, (HDEVINFO, PSP_DEVICE_INTERFACE_DATA, DWORD, DWORD));
+
+/* AdvAPI32 dependencies */
+DLL_DECLARE_HANDLE(AdvAPI32);
+DLL_DECLARE_FUNC_PREFIXED(WINAPI, LONG, p, RegQueryValueExW, (HKEY, LPCWSTR, LPDWORD, LPDWORD, LPBYTE, LPDWORD));
+DLL_DECLARE_FUNC_PREFIXED(WINAPI, LONG, p, RegCloseKey, (HKEY));
 
 /*
  * Windows DDK API definitions. Most of it copied from MinGW's includes
@@ -413,10 +420,11 @@ typedef enum USB_HUB_NODE {
 } USB_HUB_NODE;
 
 /* Cfgmgr32.dll interface */
-DLL_DECLARE(WINAPI, CONFIGRET, CM_Get_Parent, (PDEVINST, DEVINST, ULONG));
-DLL_DECLARE(WINAPI, CONFIGRET, CM_Get_Child, (PDEVINST, DEVINST, ULONG));
-DLL_DECLARE(WINAPI, CONFIGRET, CM_Get_Sibling, (PDEVINST, DEVINST, ULONG));
-DLL_DECLARE(WINAPI, CONFIGRET, CM_Get_Device_IDA, (DEVINST, PCHAR, ULONG, ULONG));
+DLL_DECLARE_HANDLE(Cfgmgr32);
+DLL_DECLARE_FUNC(WINAPI, CONFIGRET, CM_Get_Parent, (PDEVINST, DEVINST, ULONG));
+DLL_DECLARE_FUNC(WINAPI, CONFIGRET, CM_Get_Child, (PDEVINST, DEVINST, ULONG));
+DLL_DECLARE_FUNC(WINAPI, CONFIGRET, CM_Get_Sibling, (PDEVINST, DEVINST, ULONG));
+DLL_DECLARE_FUNC(WINAPI, CONFIGRET, CM_Get_Device_IDA, (DEVINST, PCHAR, ULONG, ULONG));
 
 #define IOCTL_USB_GET_HUB_CAPABILITIES_EX \
 	CTL_CODE( FILE_DEVICE_USB, USB_GET_HUB_CAPABILITIES_EX, METHOD_BUFFERED, FILE_ANY_ACCESS)
@@ -934,19 +942,20 @@ typedef struct _HIDP_VALUE_CAPS {
 	} u;
 } HIDP_VALUE_CAPS, *PHIDP_VALUE_CAPS;
 
-DLL_DECLARE(WINAPI, BOOL, HidD_GetAttributes, (HANDLE, PHIDD_ATTRIBUTES));
-DLL_DECLARE(WINAPI, VOID, HidD_GetHidGuid, (LPGUID));
-DLL_DECLARE(WINAPI, BOOL, HidD_GetPreparsedData, (HANDLE, PHIDP_PREPARSED_DATA *));
-DLL_DECLARE(WINAPI, BOOL, HidD_FreePreparsedData, (PHIDP_PREPARSED_DATA));
-DLL_DECLARE(WINAPI, BOOL, HidD_GetManufacturerString, (HANDLE, PVOID, ULONG));
-DLL_DECLARE(WINAPI, BOOL, HidD_GetProductString, (HANDLE, PVOID, ULONG));
-DLL_DECLARE(WINAPI, BOOL, HidD_GetSerialNumberString, (HANDLE, PVOID, ULONG));
-DLL_DECLARE(WINAPI, LONG, HidP_GetCaps, (PHIDP_PREPARSED_DATA, PHIDP_CAPS));
-DLL_DECLARE(WINAPI, BOOL, HidD_SetNumInputBuffers, (HANDLE, ULONG));
-DLL_DECLARE(WINAPI, BOOL, HidD_SetFeature, (HANDLE, PVOID, ULONG));
-DLL_DECLARE(WINAPI, BOOL, HidD_GetFeature, (HANDLE, PVOID, ULONG));
-DLL_DECLARE(WINAPI, BOOL, HidD_GetPhysicalDescriptor, (HANDLE, PVOID, ULONG));
-DLL_DECLARE(WINAPI, BOOL, HidD_GetInputReport, (HANDLE, PVOID, ULONG));
-DLL_DECLARE(WINAPI, BOOL, HidD_SetOutputReport, (HANDLE, PVOID, ULONG));
-DLL_DECLARE(WINAPI, BOOL, HidD_FlushQueue, (HANDLE));
-DLL_DECLARE(WINAPI, BOOL, HidP_GetValueCaps, (HIDP_REPORT_TYPE, PHIDP_VALUE_CAPS, PULONG, PHIDP_PREPARSED_DATA));
+DLL_DECLARE_HANDLE(hid);
+DLL_DECLARE_FUNC(WINAPI, BOOL, HidD_GetAttributes, (HANDLE, PHIDD_ATTRIBUTES));
+DLL_DECLARE_FUNC(WINAPI, VOID, HidD_GetHidGuid, (LPGUID));
+DLL_DECLARE_FUNC(WINAPI, BOOL, HidD_GetPreparsedData, (HANDLE, PHIDP_PREPARSED_DATA *));
+DLL_DECLARE_FUNC(WINAPI, BOOL, HidD_FreePreparsedData, (PHIDP_PREPARSED_DATA));
+DLL_DECLARE_FUNC(WINAPI, BOOL, HidD_GetManufacturerString, (HANDLE, PVOID, ULONG));
+DLL_DECLARE_FUNC(WINAPI, BOOL, HidD_GetProductString, (HANDLE, PVOID, ULONG));
+DLL_DECLARE_FUNC(WINAPI, BOOL, HidD_GetSerialNumberString, (HANDLE, PVOID, ULONG));
+DLL_DECLARE_FUNC(WINAPI, LONG, HidP_GetCaps, (PHIDP_PREPARSED_DATA, PHIDP_CAPS));
+DLL_DECLARE_FUNC(WINAPI, BOOL, HidD_SetNumInputBuffers, (HANDLE, ULONG));
+DLL_DECLARE_FUNC(WINAPI, BOOL, HidD_SetFeature, (HANDLE, PVOID, ULONG));
+DLL_DECLARE_FUNC(WINAPI, BOOL, HidD_GetFeature, (HANDLE, PVOID, ULONG));
+DLL_DECLARE_FUNC(WINAPI, BOOL, HidD_GetPhysicalDescriptor, (HANDLE, PVOID, ULONG));
+DLL_DECLARE_FUNC(WINAPI, BOOL, HidD_GetInputReport, (HANDLE, PVOID, ULONG));
+DLL_DECLARE_FUNC(WINAPI, BOOL, HidD_SetOutputReport, (HANDLE, PVOID, ULONG));
+DLL_DECLARE_FUNC(WINAPI, BOOL, HidD_FlushQueue, (HANDLE));
+DLL_DECLARE_FUNC(WINAPI, BOOL, HidP_GetValueCaps, (HIDP_REPORT_TYPE, PHIDP_VALUE_CAPS, PULONG, PHIDP_PREPARSED_DATA));
\ No newline at end of file
diff --git a/libusb/version_nano.h b/libusb/version_nano.h
index a3f68ad..b505204 100644
--- a/libusb/version_nano.h
+++ b/libusb/version_nano.h
@@ -1 +1 @@
-#define LIBUSB_NANO 11044
+#define LIBUSB_NANO 11045