Backport: Add ReleaseUnknown to safely release IUnknown* and avoid warnings when done in

noexcept context.

Backport of changeset 8286:bddda9b7df4f.

3 files changed, 22 insertions, 14 deletions

diff --git a/win32/PlatWin.cxx b/win32/PlatWin.cxx
index 75d420068..9d5d32141 100644
--- a/win32/PlatWin.cxx
+++ b/win32/PlatWin.cxx
@@ -199,9 +199,7 @@ struct FormatAndMetrics {
 		if (hfont)
 			::DeleteObject(hfont);
 #if defined(USE_D2D)
-		if (pTextFormat)
-			pTextFormat->Release();
-		pTextFormat = nullptr;
+		ReleaseUnknown(pTextFormat);
 #endif
 		extraFontFlag = 0;
 		characterSet = 0;
@@ -1143,10 +1141,7 @@ SurfaceD2D::~SurfaceD2D() {
 }
 
 void SurfaceD2D::Clear() noexcept {
-	if (pBrush) {
-		pBrush->Release();
-		pBrush = nullptr;
-	}
+	ReleaseUnknown(pBrush);
 	if (pRenderTarget) {
 		while (clipsActive) {
 			pRenderTarget->PopAxisAlignedClip();
@@ -1154,7 +1149,7 @@ void SurfaceD2D::Clear() noexcept {
 		}
 		if (ownRenderTarget) {
 			pRenderTarget->EndDraw();
-			pRenderTarget->Release();
+			ReleaseUnknown(pRenderTarget);
 			ownRenderTarget = false;
 		}
 		pRenderTarget = nullptr;
diff --git a/win32/PlatWin.h b/win32/PlatWin.h
index 2555daac0..23c889d14 100644
--- a/win32/PlatWin.h
+++ b/win32/PlatWin.h
@@ -52,6 +52,23 @@ T DLLFunction(HMODULE hModule, LPCSTR lpProcName) noexcept {
 	return fp;
 }
 
+// Release an IUnknown* and set to nullptr.
+// While IUnknown::Release must be noexcept, it isn't marked as such so produces
+// warnings which are avoided by the catch.
+template <class T>
+void ReleaseUnknown(T *&ppUnknown) noexcept {
+	if (ppUnknown) {
+		try {
+			ppUnknown->Release();
+		}
+		catch (...) {
+			// Never occurs
+		}
+		ppUnknown = nullptr;
+	}
+}
+
+
 UINT DpiForWindow(WindowID wid) noexcept;
 
 int SystemMetricsForDpi(int nIndex, UINT dpi) noexcept;
diff --git a/win32/ScintillaWin.cxx b/win32/ScintillaWin.cxx
index c33944db4..651a2629f 100644
--- a/win32/ScintillaWin.cxx
+++ b/win32/ScintillaWin.cxx
@@ -672,10 +672,7 @@ void ScintillaWin::EnsureRenderTarget(HDC hdc) {
 }
 
 void ScintillaWin::DropRenderTarget() {
-	if (pRenderTarget) {
-		pRenderTarget->Release();
-		pRenderTarget = nullptr;
-	}
+	ReleaseUnknown(pRenderTarget);
 }
 
 #endif
@@ -3533,8 +3530,7 @@ LRESULT PASCAL ScintillaWin::CTWndProc(
 #endif
 				surfaceWindow->Release();
 #if defined(USE_D2D)
-				if (pCTRenderTarget)
-					pCTRenderTarget->Release();
+				ReleaseUnknown(pCTRenderTarget);
 #endif
 				::EndPaint(hWnd, &ps);
 				return 0;