"unfortunately, a large portion of programs which call crypt are not prepared for its failure and do not check that the return value is non-null before using it. thus, always "succeeding" but giving an unmatchable hash is reportedly a better behavior than failing on error." [1]

[1] https://git.musl-libc.org/cgit/musl/commit/?id=b3c4cc121f70f...

Such a questionable decision! "Rather than let a bug in a caller (not handling the valid null output and thus crashing) surface, let's just silence it and pretend that the caller is correct! A potential clash in some situations (resulting in this vulnerability) is better than a crash!"

Maybe I should update my plea to fail loudly (https://alejo.ch/3gk) to list this as an example.