diff --git a/src/common/engine/serializer.cpp b/src/common/engine/serializer.cpp
index d500826ed6..f0d31a13dc 100644
--- a/src/common/engine/serializer.cpp
+++ b/src/common/engine/serializer.cpp
@@ -1504,7 +1504,7 @@ template<> FSerializer &Serialize(FSerializer &arc, const char *key, Dictionary
 {
 	if (arc.isWriting())
 	{
-		FString contents { dict ? DictionaryToString(*dict) : "null" };
+		FString contents { dict ? DictionaryToString(*dict) : FString("null") };
 		return arc(key, contents);
 	}
 	else
diff --git a/src/common/objects/dobject.h b/src/common/objects/dobject.h
index 3c98d144bb..98d9106a24 100644
--- a/src/common/objects/dobject.h
+++ b/src/common/objects/dobject.h
@@ -110,7 +110,7 @@ enum EInPlace { EC_InPlace };
 
 #define DECLARE_ABSTRACT_CLASS(cls,parent) \
 public: \
-	virtual PClass *StaticType() const; \
+	PClass *StaticType() const override; \
 	static ClassReg RegistrationInfo, * const RegistrationInfoPtr; \
 	typedef parent Super; \
 private: \
diff --git a/src/common/platform/posix/i_system_posix.cpp b/src/common/platform/posix/i_system_posix.cpp
index 46be3f0526..aa8bea6d29 100644
--- a/src/common/platform/posix/i_system_posix.cpp
+++ b/src/common/platform/posix/i_system_posix.cpp
@@ -35,7 +35,6 @@
 #endif // __APPLE__
 
 #include "cmdlib.h"
-#include "d_protocol.h"
 #include "i_system.h"
 #include "gameconfigfile.h"
 #include "x86.h"
diff --git a/src/common/platform/posix/sdl/sdlglvideo.cpp b/src/common/platform/posix/sdl/sdlglvideo.cpp
index ead04b73c4..da64bb9d47 100644
--- a/src/common/platform/posix/sdl/sdlglvideo.cpp
+++ b/src/common/platform/posix/sdl/sdlglvideo.cpp
@@ -51,7 +51,7 @@
 #include "gl_framebuffer.h"
 
 #ifdef HAVE_VULKAN
-#include "rendering/vulkan/system/vk_framebuffer.h"
+#include "vk_framebuffer.h"
 #endif
 
 #ifdef HAVE_SOFTPOLY
diff --git a/src/common/rendering/gl/gl_renderer.h b/src/common/rendering/gl/gl_renderer.h
index 5613fd5fd2..8b5fe7e038 100644
--- a/src/common/rendering/gl/gl_renderer.h
+++ b/src/common/rendering/gl/gl_renderer.h
@@ -20,13 +20,13 @@ class FLightBuffer;
 class DPSprite;
 class FGLRenderBuffers;
 class FGL2DDrawer;
-class FHardwareTexture;
 class SWSceneDrawer;
 class HWViewpointBuffer;
 struct FRenderViewpoint;
 
 namespace OpenGLRenderer
 {
+	class FHardwareTexture;
 	class FShaderManager;
 	class FSamplerManager;
 	class OpenGLFrameBuffer;
diff --git a/src/common/rendering/polyrenderer/backend/poly_framebuffer.h b/src/common/rendering/polyrenderer/backend/poly_framebuffer.h
index 38b8974f81..c96dfa321e 100644
--- a/src/common/rendering/polyrenderer/backend/poly_framebuffer.h
+++ b/src/common/rendering/polyrenderer/backend/poly_framebuffer.h
@@ -27,7 +27,7 @@ public:
 	PolyFrameBuffer(void *hMonitor, bool fullscreen);
 	~PolyFrameBuffer();
 
-	void Update();
+	void Update() override;
 
 	bool IsPoly() override { return true; }
 
@@ -65,7 +65,7 @@ public:
 
 private:
 	void RenderTextureView(FCanvasTexture* tex, std::function<void(IntRect &)> renderFunc) override;
-	void UpdateShadowMap();
+	void UpdateShadowMap() override;
 
 	void CheckCanvas();
 
diff --git a/src/common/rendering/polyrenderer/drawers/screen_triangle.h b/src/common/rendering/polyrenderer/drawers/screen_triangle.h
index 520ab4d000..24af616999 100644
--- a/src/common/rendering/polyrenderer/drawers/screen_triangle.h
+++ b/src/common/rendering/polyrenderer/drawers/screen_triangle.h
@@ -24,6 +24,7 @@
 
 #include <cstdint>
 #include <vector>
+#include <float.h>
 #include "renderstyle.h"
 //#include "rendering/swrenderer/drawers/r_draw.h"
 
diff --git a/src/common/rendering/vulkan/renderer/vk_postprocess.cpp b/src/common/rendering/vulkan/renderer/vk_postprocess.cpp
index c1c4148cae..6d3656fd92 100644
--- a/src/common/rendering/vulkan/renderer/vk_postprocess.cpp
+++ b/src/common/rendering/vulkan/renderer/vk_postprocess.cpp
@@ -533,10 +533,10 @@ void VkPPRenderState::RenderScreenQuad(VkPPRenderPassSetup *passSetup, VulkanDes
 	auto cmdbuffer = fb->GetDrawCommands();
 
 	VkViewport viewport = { };
-	viewport.x = x;
-	viewport.y = y;
-	viewport.width = width;
-	viewport.height = height;
+	viewport.x = (float)x;
+	viewport.y = (float)y;
+	viewport.width = (float)width;
+	viewport.height = (float)height;
 	viewport.minDepth = 0.0f;
 	viewport.maxDepth = 1.0f;
 
@@ -761,7 +761,7 @@ void VkPPRenderPassSetup::CreatePipeline(const VkPPRenderPassKey &key)
 	builder.addDynamicState(VK_DYNAMIC_STATE_SCISSOR);
 	// Note: the actual values are ignored since we use dynamic viewport+scissor states
 	builder.setViewport(0.0f, 0.0f, 320.0f, 200.0f);
-	builder.setScissor(0.0f, 0.0f, 320.0f, 200.0f);
+	builder.setScissor(0, 0, 320, 200);
 	if (key.StencilTest)
 	{
 		builder.addDynamicState(VK_DYNAMIC_STATE_STENCIL_REFERENCE);
diff --git a/src/common/rendering/vulkan/renderer/vk_renderpass.cpp b/src/common/rendering/vulkan/renderer/vk_renderpass.cpp
index 53b1cd732b..2e0973c087 100644
--- a/src/common/rendering/vulkan/renderer/vk_renderpass.cpp
+++ b/src/common/rendering/vulkan/renderer/vk_renderpass.cpp
@@ -404,7 +404,7 @@ std::unique_ptr<VulkanPipeline> VkRenderPassSetup::CreatePipeline(const VkPipeli
 
 	// Note: the actual values are ignored since we use dynamic viewport+scissor states
 	builder.setViewport(0.0f, 0.0f, 320.0f, 200.0f);
-	builder.setScissor(0, 0, 320.0f, 200.0f);
+	builder.setScissor(0, 0, 320, 200);
 
 	static const VkPrimitiveTopology vktopology[] = {
 		VK_PRIMITIVE_TOPOLOGY_POINT_LIST,
diff --git a/src/common/rendering/vulkan/system/vk_framebuffer.h b/src/common/rendering/vulkan/system/vk_framebuffer.h
index bf062afe2c..537879e6a6 100644
--- a/src/common/rendering/vulkan/system/vk_framebuffer.h
+++ b/src/common/rendering/vulkan/system/vk_framebuffer.h
@@ -68,7 +68,7 @@ public:
 	~VulkanFrameBuffer();
 	bool IsVulkan() override { return true; }
 
-	void Update();
+	void Update() override;
 
 	void InitializeState() override;
 
diff --git a/src/common/scripting/backend/codegen.h b/src/common/scripting/backend/codegen.h
index 5a0fc06644..bcadae39db 100644
--- a/src/common/scripting/backend/codegen.h
+++ b/src/common/scripting/backend/codegen.h
@@ -198,7 +198,7 @@ struct ExpVal
 
 	const FString GetString() const
 	{
-		return Type == TypeString ? *(FString *)&pointer : Type == TypeName ? FString(FName(ENamedName(Int)).GetChars()) : "";
+		return Type == TypeString ? *(FString *)&pointer : Type == TypeName ? FString(FName(ENamedName(Int)).GetChars()) : FString();
 	}
 
 	bool GetBool() const
diff --git a/src/common/scripting/core/dictionary.cpp b/src/common/scripting/core/dictionary.cpp
index b8dacd2bcd..5d4b05a3da 100644
--- a/src/common/scripting/core/dictionary.cpp
+++ b/src/common/scripting/core/dictionary.cpp
@@ -62,7 +62,7 @@ static void DictInsert(Dictionary *dict, const FString &key, const FString &valu
 static void DictAt(const Dictionary *dict, const FString &key, FString *result)
 {
 	const FString *value = dict->Map.CheckKey(key);
-	*result = value ? *value : "";
+	*result = value ? *value : FString();
 }
 
 static void DictToString(const Dictionary *dict, FString *result)
diff --git a/src/common/textures/textures.h b/src/common/textures/textures.h
index f0b5b4dfce..9ca6be736b 100644
--- a/src/common/textures/textures.h
+++ b/src/common/textures/textures.h
@@ -352,7 +352,7 @@ protected:
 	void SetFromImage();
 public:
 	FImageTexture(FImageSource* image) noexcept;
-	virtual TArray<uint8_t> Get8BitPixels(bool alphatex);
+	TArray<uint8_t> Get8BitPixels(bool alphatex) override;
 
 	void SetImage(FImageSource* img)
 	{