diff --git a/bench/ColorPrivBench.cpp b/bench/ColorPrivBench.cpp
index 404fc1f348..23cc48f3cc 100644
--- a/bench/ColorPrivBench.cpp
+++ b/bench/ColorPrivBench.cpp
@@ -41,7 +41,7 @@ public:
 
     void onDraw(int loops, SkCanvas*) override {
         // We xor results of FourByteInterp into junk to make sure the function runs.
-        volatile SkPMColor junk = 0;
+        SK_MAYBE_UNUSED volatile SkPMColor junk = 0;
 
         for (int loop = 0; loop < loops; loop++) {
             for (int i = 0; i < kInputs; i++) {
diff --git a/bench/ControlBench.cpp b/bench/ControlBench.cpp
index f8e15c9711..19696934ab 100644
--- a/bench/ControlBench.cpp
+++ b/bench/ControlBench.cpp
@@ -16,7 +16,7 @@ struct ControlBench : public Benchmark {
 
     void onDraw(int loops, SkCanvas*) override {
         // Nothing terribly useful: force a memory read, a memory write, and some math.
-        volatile uint32_t rand = 0;
+        SK_MAYBE_UNUSED volatile uint32_t rand = 0;
         for (int i = 0; i < 1000*loops; i++) {
             rand *= 1664525;
             rand += 1013904223;
diff --git a/bench/MatrixBench.cpp b/bench/MatrixBench.cpp
index 4aa745eef6..07683ead7e 100644
--- a/bench/MatrixBench.cpp
+++ b/bench/MatrixBench.cpp
@@ -53,7 +53,7 @@ protected:
         m2.reset();
 
         // xor into a volatile prevents these comparisons from being optimized away.
-        volatile bool junk = false;
+        SK_MAYBE_UNUSED volatile bool junk = false;
         junk ^= (m0 == m1);
         junk ^= (m1 == m2);
         junk ^= (m2 == m0);
@@ -116,7 +116,7 @@ protected:
                        fArray[3], fArray[4], fArray[5],
                        fArray[6], fArray[7], fArray[8]);
         // xoring into a volatile prevents the compiler from optimizing these away
-        volatile int junk = 0;
+        SK_MAYBE_UNUSED volatile int junk = 0;
         junk ^= (fMatrix.getType());
         fMatrix.dirtyMatrixTypeCache();
         junk ^= (fMatrix.getType());
diff --git a/bench/ScalarBench.cpp b/bench/ScalarBench.cpp
index 68c0884804..9148532654 100644
--- a/bench/ScalarBench.cpp
+++ b/bench/ScalarBench.cpp
@@ -59,7 +59,7 @@ protected:
     int mulLoopCount() const override { return 4; }
     void performTest() override {
         // xoring into a volatile prevents the compiler from optimizing these checks away.
-        volatile bool junk = false;
+        SK_MAYBE_UNUSED volatile bool junk = false;
         junk ^= (fArray[6] != 0.0f || fArray[7] != 0.0f || fArray[8] != 1.0f);
         junk ^= (fArray[2] != 0.0f || fArray[5] != 0.0f);
     }
@@ -78,7 +78,7 @@ protected:
     int mulLoopCount() const override { return 4; }
     void performTest() override {
         // xoring into a volatile prevents the compiler from optimizing these checks away.
-        volatile int32_t junk = 0;
+        SK_MAYBE_UNUSED volatile int32_t junk = 0;
         junk ^= (SkScalarAs2sCompliment(fArray[6]) |
                  SkScalarAs2sCompliment(fArray[7]) |
                 (SkScalarAs2sCompliment(fArray[8]) - kPersp1Int));
diff --git a/fuzz/FuzzMain.cpp b/fuzz/FuzzMain.cpp
index 6f6a535eba..1a9e7fae9d 100644
--- a/fuzz/FuzzMain.cpp
+++ b/fuzz/FuzzMain.cpp
@@ -592,12 +592,7 @@ static void fuzz_img(sk_sp<SkData> bytes, uint8_t scale, uint8_t mode) {
             SkBitmap subsetBm;
             // We will reuse pixel memory from bitmap.
             void* pixels = bitmap.getPixels();
-            // Keep track of left and top (for drawing subsetBm into canvas). We could use
-            // fscale * x and fscale * y, but we want integers such that the next subset will start
-            // where the last one ended. So we'll add decodeInfo.width() and height().
-            int left = 0;
             for (int x = 0; x < W; x += w) {
-                int top = 0;
                 for (int y = 0; y < H; y+= h) {
                     // Do not make the subset go off the edge of the image.
                     const int preScaleW = std::min(w, W - x);
@@ -645,11 +640,7 @@ static void fuzz_img(sk_sp<SkData> bytes, uint8_t scale, uint8_t mode) {
                                                   W, H, result);
                             return;
                     }
-                    // translate by the scaled height.
-                    top += decodeInfo.height();
                 }
-                // translate by the scaled width.
-                left += decodeInfo.width();
             }
             SkDebugf("[terminated] Success!\n");
             break;
diff --git a/gm/rasterhandleallocator.cpp b/gm/rasterhandleallocator.cpp
index 340b03354b..fa4488bb3a 100644
--- a/gm/rasterhandleallocator.cpp
+++ b/gm/rasterhandleallocator.cpp
@@ -255,7 +255,7 @@ public:
 
         RECT clip_bounds_RECT = toRECT(clip_bounds);
         HRGN hrgn = CreateRectRgnIndirect(&clip_bounds_RECT);
-        int result = SelectClipRgn(hdc, hrgn);
+        SK_MAYBE_UNUSED int result = SelectClipRgn(hdc, hrgn);
         SkASSERT(result != ERROR);
         result = DeleteObject(hrgn);
         SkASSERT(result != 0);
diff --git a/src/gpu/d3d/GrD3DGpu.cpp b/src/gpu/d3d/GrD3DGpu.cpp
index 1edeee76d3..958a482c90 100644
--- a/src/gpu/d3d/GrD3DGpu.cpp
+++ b/src/gpu/d3d/GrD3DGpu.cpp
@@ -740,11 +740,8 @@ bool GrD3DGpu::uploadToTexture(GrD3DTexture* tex,
 
     int currentWidth = rect.width();
     int currentHeight = rect.height();
-    int layerHeight = tex->height();
-
     for (int currentMipLevel = 0; currentMipLevel < mipLevelCount; currentMipLevel++) {
         if (texels[currentMipLevel].fPixels) {
-            SkASSERT(1 == mipLevelCount || currentHeight == layerHeight);
 
             const size_t trimRowBytes = currentWidth * bpp;
             const size_t srcRowBytes = texels[currentMipLevel].fRowBytes;
@@ -758,7 +755,6 @@ bool GrD3DGpu::uploadToTexture(GrD3DTexture* tex,
         }
         currentWidth = std::max(1, currentWidth / 2);
         currentHeight = std::max(1, currentHeight / 2);
-        layerHeight = currentHeight;
     }
 
     // Update the offsets in the footprints to be relative to the slice's offset
diff --git a/src/gpu/mtl/GrMtlGpu.mm b/src/gpu/mtl/GrMtlGpu.mm
index fcb44c4966..9f9b3d1352 100644
--- a/src/gpu/mtl/GrMtlGpu.mm
+++ b/src/gpu/mtl/GrMtlGpu.mm
@@ -1339,16 +1339,6 @@ bool GrMtlGpu::onReadPixels(GrSurface* surface,
     size_t transBufferRowBytes = bpp*rect.width();
     size_t transBufferImageBytes = transBufferRowBytes*rect.height();
 
-    // TODO: implement some way of reusing buffers instead of making a new one every time.
-    NSUInteger options = 0;
-    if (@available(macOS 10.11, iOS 9.0, *)) {
-#ifdef SK_BUILD_FOR_MAC
-        options |= MTLResourceStorageModeManaged;
-#else
-        options |= MTLResourceStorageModeShared;
-#endif
-    }
-
     GrResourceProvider* resourceProvider = this->getContext()->priv().resourceProvider();
     sk_sp<GrGpuBuffer> transferBuffer = resourceProvider->createBuffer(
             transBufferImageBytes, GrGpuBufferType::kXferGpuToCpu,
diff --git a/src/gpu/vk/GrVkGpu.cpp b/src/gpu/vk/GrVkGpu.cpp
index 4c4e06c56c..656397aaf1 100644
--- a/src/gpu/vk/GrVkGpu.cpp
+++ b/src/gpu/vk/GrVkGpu.cpp
@@ -919,10 +919,8 @@ bool GrVkGpu::uploadTexDataOptimal(GrVkAttachment* texAttachment,
 
     int currentWidth = rect.width();
     int currentHeight = rect.height();
-    int layerHeight = texAttachment->height();
     for (int currentMipLevel = 0; currentMipLevel < mipLevelCount; currentMipLevel++) {
         if (texelsShallowCopy[currentMipLevel].fPixels) {
-            SkASSERT(1 == mipLevelCount || currentHeight == layerHeight);
             const size_t trimRowBytes = currentWidth * bpp;
             const size_t rowBytes = texelsShallowCopy[currentMipLevel].fRowBytes;
 
@@ -943,8 +941,6 @@ bool GrVkGpu::uploadTexDataOptimal(GrVkAttachment* texAttachment,
 
         currentWidth  = std::max(1,  currentWidth/2);
         currentHeight = std::max(1, currentHeight/2);
-
-        layerHeight = currentHeight;
     }
 
     // Change layout of our target so it can be copied to
diff --git a/src/sksl/SkSLDehydrator.cpp b/src/sksl/SkSLDehydrator.cpp
index ab55f3f10a..522571c4bf 100644
--- a/src/sksl/SkSLDehydrator.cpp
+++ b/src/sksl/SkSLDehydrator.cpp
@@ -239,12 +239,12 @@ void Dehydrator::write(const SymbolTable& symbols) {
         ordered.insert({name, symbol});
     });
     for (std::pair<skstd::string_view, const Symbol*> p : ordered) {
-        bool found = false;
+        SkDEBUGCODE(bool found = false;)
         for (size_t i = 0; i < symbols.fOwnedSymbols.size(); ++i) {
             if (symbols.fOwnedSymbols[i].get() == p.second) {
                 fCommandBreaks.add(fBody.bytesWritten());
                 this->writeU16(i);
-                found = true;
+                SkDEBUGCODE(found = true;)
                 break;
             }
         }
diff --git a/tools/sk_app/win/Window_win.cpp b/tools/sk_app/win/Window_win.cpp
index cf39afd9b3..353125a09b 100644
--- a/tools/sk_app/win/Window_win.cpp
+++ b/tools/sk_app/win/Window_win.cpp
@@ -210,7 +210,6 @@ static skui::ModifierKey get_modifiers(UINT message, WPARAM wParam, LPARAM lPara
 LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
 {
     PAINTSTRUCT ps;
-    HDC hdc;
 
     Window_win* window = (Window_win*) GetWindowLongPtr(hWnd, GWLP_USERDATA);
 
@@ -218,7 +217,7 @@ LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
 
     switch (message) {
         case WM_PAINT:
-            hdc = BeginPaint(hWnd, &ps);
+            BeginPaint(hWnd, &ps);
             window->onPaint();
             EndPaint(hWnd, &ps);
             eventHandled = true;