diff --git a/repos/gems/include/gems/animator.h b/repos/gems/include/gems/animator.h
index 2ebaed4074..996a5638e9 100644
--- a/repos/gems/include/gems/animator.h
+++ b/repos/gems/include/gems/animator.h
@@ -28,7 +28,7 @@ class Animator
 
 		friend class Item;
 
-		Genode::List<Genode::List_element<Item> > _items;
+		Genode::List<Genode::List_element<Item> > _items { };
 
 	public:
 
diff --git a/repos/gems/include/gems/file.h b/repos/gems/include/gems/file.h
index e35dca2a57..7ae5d385e2 100644
--- a/repos/gems/include/gems/file.h
+++ b/repos/gems/include/gems/file.h
@@ -21,6 +21,12 @@ class File
 {
 	private:
 
+		/*
+		 * Noncopyable
+		 */
+		File(File const &);
+		File & operator = (File const &);
+
 		Genode::Allocator   &_alloc;
 		Genode::size_t const _file_size;
 		void                *_data;
diff --git a/repos/gems/include/gems/png_image.h b/repos/gems/include/gems/png_image.h
index a7c3339381..36c783e475 100644
--- a/repos/gems/include/gems/png_image.h
+++ b/repos/gems/include/gems/png_image.h
@@ -49,90 +49,120 @@ class Png_image
 		Genode::Region_map  &_rm;
 		Genode::Allocator   &_alloc;
 
-		struct Read_struct
+		class Read_struct
 		{
-			/* start of PNG data */
-			png_bytep const data;
+			private:
 
-			/* read position, maintained by 'read_callback' */
-			unsigned pos = 0;
+				/*
+				 * Noncopyable
+				 */
+				Read_struct(Read_struct const &);
+				Read_struct & operator = (Read_struct const &);
 
-			static void callback(png_structp png_ptr, png_bytep dst, png_size_t len)
-			{
-				Read_struct &read_struct = *(Read_struct *)png_get_io_ptr(png_ptr);
-				Genode::memcpy(dst, read_struct.data + read_struct.pos, len);
-				read_struct.pos += len;
-			}
+			public:
 
-			png_structp png_ptr =
-				_assert_non_null<Read_struct_failed>(
-					png_create_read_struct(PNG_LIBPNG_VER_STRING, 0, 0, 0));
+				/* start of PNG data */
+				png_bytep const data;
 
-			Read_struct(void *data) : data((png_bytep)data)
-			{
-				png_set_read_fn(png_ptr, this, callback);
-			}
+				/* read position, maintained by 'read_callback' */
+				unsigned pos = 0;
 
-			~Read_struct()
-			{
-				png_destroy_read_struct(&png_ptr, nullptr, nullptr);
-			}
+				static void callback(png_structp png_ptr, png_bytep dst, png_size_t len)
+				{
+					Read_struct &read_struct = *(Read_struct *)png_get_io_ptr(png_ptr);
+					Genode::memcpy(dst, read_struct.data + read_struct.pos, len);
+					read_struct.pos += len;
+				}
+
+				png_structp png_ptr =
+					_assert_non_null<Read_struct_failed>(
+						png_create_read_struct(PNG_LIBPNG_VER_STRING, 0, 0, 0));
+
+				Read_struct(void *data) : data((png_bytep)data)
+				{
+					png_set_read_fn(png_ptr, this, callback);
+				}
+
+				~Read_struct()
+				{
+					png_destroy_read_struct(&png_ptr, nullptr, nullptr);
+				}
 		};
 
 		Read_struct _read_struct;
 
-		struct Info
+		class Info
 		{
-			png_structp png_ptr;
-			png_infop   info_ptr;
+			private:
 
-			int         bit_depth, color_type, interlace_type;
-			png_uint_32 img_w, img_h;
+				/*
+				 * Noncopyable
+				 */
+				Info(Info const &);
+				Info & operator = (Info const &);
 
-			Info(png_structp png_ptr)
-			:
-				png_ptr(png_ptr),
-				info_ptr(_assert_non_null<Info_failed>(png_create_info_struct(png_ptr)))
-			{
-				png_read_info(png_ptr, info_ptr);
+			public:
 
-				png_get_IHDR(png_ptr, info_ptr, &img_w, &img_h, &bit_depth, &color_type,
-				             &interlace_type, nullptr, nullptr);
+				png_structp png_ptr;
+				png_infop   info_ptr;
 
-				if (color_type == PNG_COLOR_TYPE_PALETTE)
-					png_set_palette_to_rgb(png_ptr);
+				int         bit_depth = 0, color_type = 0, interlace_type = 0;
+				png_uint_32 img_w = 0, img_h = 0;
 
-				if (color_type == PNG_COLOR_TYPE_GRAY || color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
-					png_set_gray_to_rgb(png_ptr);
+				Info(png_structp png_ptr)
+				:
+					png_ptr(png_ptr),
+					info_ptr(_assert_non_null<Info_failed>(png_create_info_struct(png_ptr)))
+				{
+					png_read_info(png_ptr, info_ptr);
 
-				if (bit_depth <   8) png_set_packing(png_ptr);
-				if (bit_depth == 16) png_set_strip_16(png_ptr);
-			}
+					png_get_IHDR(png_ptr, info_ptr, &img_w, &img_h, &bit_depth, &color_type,
+					             &interlace_type, nullptr, nullptr);
 
-			~Info()
-			{
-				png_destroy_info_struct(png_ptr, &info_ptr);
-			}
+					if (color_type == PNG_COLOR_TYPE_PALETTE)
+						png_set_palette_to_rgb(png_ptr);
+
+					if (color_type == PNG_COLOR_TYPE_GRAY || color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
+						png_set_gray_to_rgb(png_ptr);
+
+					if (bit_depth <   8) png_set_packing(png_ptr);
+					if (bit_depth == 16) png_set_strip_16(png_ptr);
+				}
+
+				~Info()
+				{
+					png_destroy_info_struct(png_ptr, &info_ptr);
+				}
 
 		} _info { _read_struct.png_ptr };
 
-		struct Row
+		class Row
 		{
-			Genode::Allocator &alloc;
-			size_t const row_num_bytes;
-			png_bytep const row_ptr;
+			private:
 
-			Row(Genode::Allocator &alloc, png_structp png_ptr, png_infop info_ptr)
-			:
-				alloc(alloc),
-				row_num_bytes(png_get_rowbytes(png_ptr, info_ptr)*8),
-				row_ptr((png_bytep)alloc.alloc(row_num_bytes))
-			{ }
+				/*
+				 * Noncopyable
+				 */
+				Row(Row const &);
+				Row & operator = (Row const &);
 
-			~Row()
-			{
-				alloc.free(row_ptr, row_num_bytes);
-			}
+			public:
+
+				Genode::Allocator &alloc;
+				size_t const row_num_bytes;
+				png_bytep const row_ptr;
+
+				Row(Genode::Allocator &alloc, png_structp png_ptr, png_infop info_ptr)
+				:
+					alloc(alloc),
+					row_num_bytes(png_get_rowbytes(png_ptr, info_ptr)*8),
+					row_ptr((png_bytep)alloc.alloc(row_num_bytes))
+				{ }
+
+				~Row()
+				{
+					alloc.free(row_ptr, row_num_bytes);
+				}
 		} _row { _alloc, _read_struct.png_ptr, _info.info_ptr };
 
 	public:
diff --git a/repos/gems/include/polygon_gfx/interpolate_rgba.h b/repos/gems/include/polygon_gfx/interpolate_rgba.h
index 7be032d373..eeb127f0f1 100644
--- a/repos/gems/include/polygon_gfx/interpolate_rgba.h
+++ b/repos/gems/include/polygon_gfx/interpolate_rgba.h
@@ -36,7 +36,7 @@ static inline void Polygon::interpolate_rgba(Polygon::Color start,
                                              PT *dst,
                                              unsigned char *dst_alpha,
                                              unsigned num_values,
-                                             int x, int y)
+                                             int, int)
 {
 	/* sanity check */
 	if (num_values == 0) return;