WinAdapter: Add three missing virtual functions to IMalloc interface

To prevent unexpected vtable breakage, add the missing functions from
the [documentation].  Note that they are listed in the wrong order, the
right order is retrieved from the `ObjIdl.h` header and implementations
for `IMalloc` in DirectXShaderCompiler.  All implementations are now
properly using the `override` keyword too, to enforce virtual method
existence in the base class.

[documentation]: https://docs.microsoft.com/en-us/windows/win32/api/objidl/nn-objidl-imalloc

include/dxc/Support/WinAdapter.h

@@ -632,6 +632,9 @@ struct IMalloc : public IUnknown {
   virtual void *Alloc(size_t size) = 0;
   virtual void *Realloc(void *ptr, size_t size) = 0;
   virtual void Free(void *ptr) = 0;
+  virtual size_t GetSize(void *pv) = 0;
+  virtual int DidAlloc(void *pv) = 0;
+  virtual void HeapMinimize(void) = 0;
 };
 
 CROSS_PLATFORM_UUIDOF(ISequentialStream, "0C733A30-2A1C-11CE-ADE5-00AA0044773D")

lib/DxcSupport/FileIOHelper.cpp

@@ -68,14 +68,14 @@ struct HeapMalloc final : public IMalloc {
 
   SIZE_T STDMETHODCALLTYPE GetSize(
     /* [annotation][in] */
-    _In_opt_ _Post_writable_byte_size_(return)  void *pv)
+    _In_opt_ _Post_writable_byte_size_(return)  void *pv) override
   {
     return HeapSize(GetProcessHeap(), 0, pv);
   }
 
   int STDMETHODCALLTYPE DidAlloc(
     /* [annotation][in] */
-    _In_opt_  void *pv)
+    _In_opt_  void *pv) override
   {
     return -1; // don't know
   }

lib/DxcSupport/WinFunctions.cpp

@@ -167,6 +167,9 @@ struct CoMalloc final : public IMalloc {
   void *STDMETHODCALLTYPE Alloc(size_t size) override { return malloc(size); }
   void *STDMETHODCALLTYPE Realloc(void *ptr, size_t size) override { return realloc(ptr, size); }
   void STDMETHODCALLTYPE Free(void *ptr) override { free(ptr); }
+  size_t STDMETHODCALLTYPE GetSize(void *pv) override { return -1; }
+  int STDMETHODCALLTYPE DidAlloc(void *pv) override { return -1; }
+  void STDMETHODCALLTYPE HeapMinimize(void) override {}
 
 private:
   DXC_MICROCOM_REF_FIELD(m_dwRef)

tools/clang/unittests/HLSL/CompilerTest.cpp

@@ -2841,17 +2841,17 @@ struct InstrumentedHeapMalloc : public IMalloc {
     m_FailAlloc = index;
   }
 
-  ULONG STDMETHODCALLTYPE AddRef() {
+  ULONG STDMETHODCALLTYPE AddRef() override {
     return ++m_RefCount;
   }
-  ULONG STDMETHODCALLTYPE Release() {
+  ULONG STDMETHODCALLTYPE Release() override {
     if (m_RefCount == 0) VERIFY_FAIL();
     return --m_RefCount;
   }
-  STDMETHODIMP QueryInterface(REFIID iid, void** ppvObject) {
+  STDMETHODIMP QueryInterface(REFIID iid, void** ppvObject) override {
     return DoBasicQueryInterface<IMalloc>(this, iid, ppvObject);
   }
-  virtual void *STDMETHODCALLTYPE Alloc(_In_ SIZE_T cb) {
+  virtual void *STDMETHODCALLTYPE Alloc(_In_ SIZE_T cb) override {
     ++m_AllocCount;
     if (m_FailAlloc && m_AllocCount >= m_FailAlloc) {
       return nullptr; // breakpoint for i failure - m_FailAlloc == 1+VAL
@@ -2875,7 +2875,7 @@ struct InstrumentedHeapMalloc : public IMalloc {
     return P + 1;
   }
 
-  virtual void *STDMETHODCALLTYPE Realloc(_In_opt_ void *pv, _In_ SIZE_T cb) {
+  virtual void *STDMETHODCALLTYPE Realloc(_In_opt_ void *pv, _In_ SIZE_T cb) override {
     SIZE_T priorSize = pv == nullptr ? (SIZE_T)0 : GetSize(pv);
     void *R = Alloc(cb);
     if (!R)
@@ -2886,7 +2886,7 @@ struct InstrumentedHeapMalloc : public IMalloc {
     return R;
   }
 
-  virtual void STDMETHODCALLTYPE Free(_In_opt_ void *pv) {
+  virtual void STDMETHODCALLTYPE Free(_In_opt_ void *pv) override {
     if (!pv)
       return;
     PtrData *P = DataFromPtr(pv);
@@ -2904,18 +2904,18 @@ struct InstrumentedHeapMalloc : public IMalloc {
 
   virtual SIZE_T STDMETHODCALLTYPE GetSize(
     /* [annotation][in] */
-    _In_opt_ _Post_writable_byte_size_(return)  void *pv)
+    _In_opt_ _Post_writable_byte_size_(return)  void *pv) override
   {
     if (pv == nullptr) return 0;
     return DataFromPtr(pv)->Size;
   }
 
   virtual int STDMETHODCALLTYPE DidAlloc(
-      _In_opt_ void *pv) {
+      _In_opt_ void *pv) override {
     return -1; // don't know
   }
 
-  virtual void STDMETHODCALLTYPE HeapMinimize(void) {}
+  virtual void STDMETHODCALLTYPE HeapMinimize(void) override {}
 
   void DumpLeaks() {
     PtrData *ptr = (PtrData*)AllocList.Flink;;