The program I was compiling (a CLI wall-clock) is thrice bigger with musl than with diet. Most binaries of your software are *smaller* with musl, a notable exception being s6-mount (almost twice with musl!).
That's probably stdio. musl's stdio is scrupulously conformant whereas diet's stdio isn't, so musl's is bigger. (It takes a lot of effort, and a lot of code, to correctly implement that demented specification.) s6-mount uses getmntent() for /etc/fstab parsing, which pulls in the FILE structure and likely a good portion of stdio. -- Laurent
