Hi, thank you for libspng! I recently did a comparasion of different png libs (libpng, lodepng), and found libspng very robust except some cases that other libs report an error or a warnning and libspng accepts it. I test it with example.c and the png file is attached test.zip!

Specifically, libpng report a warning libpng warning: IDAT: invalid distance too far back under its function png_read_IDAT_data at png_read_IDAT_data, and lodepng reject it with an error at inflateHuffmanBlock.
I also tested it with other online checker, such as extract-metadata, it also reports a warnning message Warning: [minor] Trailer data after PNG IEND chunk .
It seems that libspng should check something of the chunk but I am not sure, also unclear whether it will have other effects.

Hope it helps.