[clang] Add DllMain entry point to `libclang.dll` (PR #171465)

[Hans Wennborg via cfe-commits]

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@@ -0,0 +1,24 @@
+
+
+#include <windows.h>
+
+extern "C" {
+
+int rpmalloc_initialize(void);
+void rpmalloc_finalize(void);
+void rpmalloc_thread_initialize(void);
+void rpmalloc_thread_finalize(int release_caches);
+
+BOOL WINAPI DllMain(HINSTANCE instance, DWORD reason, LPVOID reserved) {
+  if (reason == DLL_PROCESS_ATTACH) {
+    rpmalloc_initialize();
+  } else if (reason == DLL_PROCESS_DETACH) {
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zmodem wrote:

Since we build rpmalloc with `ENABLE_PRELOAD`, I think we already call `_global_rpmalloc_init()` at load time, so maybe we shouldn't be doing the initialization calls here?

https://github.com/llvm/llvm-project/pull/171465