Less explicit memory management in Irrlicht image writer classes (#15493)

CImageWriterPNG::writeImage() and writeJPEGFile() explicitly allocate
and deallocate memory with `new` and `delete`, which is prone to programming errors.
The code also has non-functional error handling:
When memory allocation fails, `new` throws an `std::bad_alloc` exception
and never returns `nullptr`, so the check for `nullptr` is always false.

Co-authored-by: DS <ds.desour@proton.me>

irr/src/CImageWriterJPG.cpp

@@ -10,6 +10,7 @@
 #include "os.h"
 
 #include <cstdio> // IWYU pragma: keep (required for jpeglib.h)
+#include <memory>
 #include <jpeglib.h>
 #include <jerror.h>
 
@@ -130,32 +131,28 @@ static bool writeJPEGFile(io::IWriteFile *file, IImage *image, u32 quality)
 	jpeg_set_quality(&cinfo, quality, TRUE);
 	jpeg_start_compress(&cinfo, TRUE);
 
-	u8 *dest = new u8[dim.Width * 3];
+	std::unique_ptr<u8[]> dest{new u8[dim.Width * 3]};
 
-	if (dest) {
+	const u32 pitch = image->getPitch();
-		const u32 pitch = image->getPitch();
+	JSAMPROW row_pointer[1]; /* pointer to JSAMPLE row[s] */
-		JSAMPROW row_pointer[1]; /* pointer to JSAMPLE row[s] */
+	row_pointer[0] = dest.get();
-		row_pointer[0] = dest;
 
-		u8 *src = (u8 *)image->getData();
+	u8 *src = (u8 *)image->getData();
 
-		while (cinfo.next_scanline < cinfo.image_height) {
+	while (cinfo.next_scanline < cinfo.image_height) {
-			// convert next line
+		// convert next line
-			format(src, dim.Width, dest);
+		format(src, dim.Width, dest.get());
-			src += pitch;
+		src += pitch;
-			jpeg_write_scanlines(&cinfo, row_pointer, 1);
+		jpeg_write_scanlines(&cinfo, row_pointer, 1);
-		}
-
-		delete[] dest;
-
-		/* Step 6: Finish compression */
-		jpeg_finish_compress(&cinfo);
 	}
 
+	/* Step 6: Finish compression */
+	jpeg_finish_compress(&cinfo);
+
 	/* Step 7: Destroy */
 	jpeg_destroy_compress(&cinfo);
 
-	return (dest != 0);
+	return true;
 }
 
 } // namespace video

irr/src/CImageWriterPNG.cpp

@@ -10,6 +10,7 @@
 #include "os.h" // for logging
 
 #include <png.h> // use system lib png
+#include <memory>
 
 namespace irr
 {
@@ -94,22 +95,23 @@ bool CImageWriterPNG::writeImage(io::IWriteFile *file, IImage *image, u32 param)
 	png_set_write_fn(png_ptr, file, user_write_data_fcn, NULL);
 
 	// Set info
+	core::dimension2d<u32> img_dim = image->getDimension();
 	switch (image->getColorFormat()) {
 	case ECF_A8R8G8B8:
 	case ECF_A1R5G5B5:
 		png_set_IHDR(png_ptr, info_ptr,
-				image->getDimension().Width, image->getDimension().Height,
+				img_dim.Width, img_dim.Height,
 				8, PNG_COLOR_TYPE_RGB_ALPHA, PNG_INTERLACE_NONE,
 				PNG_COMPRESSION_TYPE_DEFAULT, PNG_FILTER_TYPE_DEFAULT);
 		break;
 	default:
 		png_set_IHDR(png_ptr, info_ptr,
-				image->getDimension().Width, image->getDimension().Height,
+				img_dim.Width, img_dim.Height,
 				8, PNG_COLOR_TYPE_RGB, PNG_INTERLACE_NONE,
 				PNG_COMPRESSION_TYPE_DEFAULT, PNG_FILTER_TYPE_DEFAULT);
 	}
 
-	s32 lineWidth = image->getDimension().Width;
+	s32 lineWidth = img_dim.Width;
 	switch (image->getColorFormat()) {
 	case ECF_R8G8B8:
 	case ECF_R5G6B5:
@@ -123,61 +125,52 @@ bool CImageWriterPNG::writeImage(io::IWriteFile *file, IImage *image, u32 param)
 	default:
 		break;
 	}
-	u8 *tmpImage = new u8[image->getDimension().Height * lineWidth];
+	std::unique_ptr<u8[]> tmpImage{new u8[img_dim.Height * lineWidth]};
-	if (!tmpImage) {
-		os::Printer::log("PNGWriter: Internal PNG create image failure", file->getFileName(), ELL_ERROR);
-		png_destroy_write_struct(&png_ptr, &info_ptr);
-		return false;
-	}
 
+	auto num_pixels = img_dim.Height * img_dim.Width;
 	u8 *data = (u8 *)image->getData();
 	switch (image->getColorFormat()) {
 	case ECF_R8G8B8:
-		CColorConverter::convert_R8G8B8toR8G8B8(data, image->getDimension().Height * image->getDimension().Width, tmpImage);
+		CColorConverter::convert_R8G8B8toR8G8B8(data, num_pixels,
+			tmpImage.get());
 		break;
 	case ECF_A8R8G8B8:
-		CColorConverter::convert_A8R8G8B8toA8R8G8B8(data, image->getDimension().Height * image->getDimension().Width, tmpImage);
+		CColorConverter::convert_A8R8G8B8toA8R8G8B8(data, num_pixels,
+			tmpImage.get());
 		break;
 	case ECF_R5G6B5:
-		CColorConverter::convert_R5G6B5toR8G8B8(data, image->getDimension().Height * image->getDimension().Width, tmpImage);
+		CColorConverter::convert_R5G6B5toR8G8B8(data, num_pixels,
+			tmpImage.get());
 		break;
 	case ECF_A1R5G5B5:
-		CColorConverter::convert_A1R5G5B5toA8R8G8B8(data, image->getDimension().Height * image->getDimension().Width, tmpImage);
+		CColorConverter::convert_A1R5G5B5toA8R8G8B8(data, num_pixels,
+			tmpImage.get());
 		break;
 		// TODO: Error handling in case of unsupported color format
 	default:
 		os::Printer::log("CImageWriterPNG does not support image format", ColorFormatNames[image->getColorFormat()], ELL_WARNING);
 		png_destroy_write_struct(&png_ptr, &info_ptr);
-		delete[] tmpImage;
 		return false;
 	}
 
 	// Create array of pointers to rows in image data
 
 	// Used to point to image rows
-	u8 **RowPointers = new png_bytep[image->getDimension().Height];
+	std::unique_ptr<u8*[]> RowPointers{new u8*[img_dim.Height]};
-	if (!RowPointers) {
-		os::Printer::log("PNGWriter: Internal PNG create row pointers failure", file->getFileName(), ELL_ERROR);
-		png_destroy_write_struct(&png_ptr, &info_ptr);
-		delete[] tmpImage;
-		return false;
-	}
 
-	data = tmpImage;
+	data = tmpImage.get();
 	// Fill array of pointers to rows in image data
-	for (u32 i = 0; i < image->getDimension().Height; ++i) {
+	for (u32 i = 0; i < img_dim.Height; ++i) {
 		RowPointers[i] = data;
 		data += lineWidth;
 	}
 	// for proper error handling
 	if (setjmp(png_jmpbuf(png_ptr))) {
 		png_destroy_write_struct(&png_ptr, &info_ptr);
-		delete[] RowPointers;
-		delete[] tmpImage;
 		return false;
 	}
 
-	png_set_rows(png_ptr, info_ptr, RowPointers);
+	png_set_rows(png_ptr, info_ptr, RowPointers.get());
 
 	if (image->getColorFormat() == ECF_A8R8G8B8 || image->getColorFormat() == ECF_A1R5G5B5)
 		png_write_png(png_ptr, info_ptr, PNG_TRANSFORM_BGR, NULL);
@@ -185,8 +178,6 @@ bool CImageWriterPNG::writeImage(io::IWriteFile *file, IImage *image, u32 param)
 		png_write_png(png_ptr, info_ptr, PNG_TRANSFORM_IDENTITY, NULL);
 	}
 
-	delete[] RowPointers;
-	delete[] tmpImage;
 	png_destroy_write_struct(&png_ptr, &info_ptr);
 	return true;
 }