Windows: Use GetModuleHandleEx instead of LoadLibrary

We were using an anti-pattern of:
 - LoadLibrary
 - GetProcAddress
 - FreeLibrary

This is problematic because of several reasons:
 - We are holding on to pointers into a library we just unloaded.
 - Calling LoadLibrary results in an increase in the reference count of
   the library in question and any libraries that it depends on and
   so-on and so-forth.  This is none too quick.

Instead, use GetModuleHandleEx with GET_MODULE_HANDLE_EX_FLAG_PIN.  This
is done because because we didn't bring the reference for the library
into existence and therefor shouldn't count on it being around later.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@192550 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Support/Windows/RWMutex.inc b/lib/Support/Windows/RWMutex.inc
index e4c2308f349418092ee744891f50366f75b26076..7d158288672a926c627e03be4bbafdef86c31bf8 100644 (file)
--- a/lib/Support/Windows/RWMutex.inc
+++ b/lib/Support/Windows/RWMutex.inc
@@ -48,7 +48,8 @@ static bool loadSRW() {
   if (!sChecked) {
     sChecked = true;
 
-    HMODULE hLib = ::LoadLibraryW(L"Kernel32.dll");
+    HMODULE hLib;
+    ::GetModuleHandleExW(GET_MODULE_HANDLE_EX_FLAG_PIN, L"Kernel32.dll", &hLib);
     if (hLib) {
       fpInitializeSRWLock =
         (VOID (WINAPI *)(PSRWLOCK))::GetProcAddress(hLib,
@@ -65,7 +66,6 @@ static bool loadSRW() {
       fpReleaseSRWLockShared =
         (VOID (WINAPI *)(PSRWLOCK))::GetProcAddress(hLib,
                                                "ReleaseSRWLockShared");
-      ::FreeLibrary(hLib);
 
       if (fpInitializeSRWLock != NULL) {
         sHasSRW = true;