This was done initially as part of the visibility jam: https://handmade.network/jam/visibility-2023/feed
It is a CLI application. Given a list of files or a folder it will parse all the C structures in the files provided, calculate their member's alignments and sizes, and spit out an interactive single html file for visualization. Here's it is just parsing the data structures in its own source code.
I'd like to support bitfields, attribute noalign, __randomize_layout, C++, other languages, and have better/more useful tools for doing things like sorting them by size, showing you where you can trivially make your structures smaller, etc. and more in the future.