Zed_utf8.singleton when I decode something with base64 package

[dinosaure]

──────────────────────────────────────────────────────────────────────────┬─────────────────────────────────────────────────────────────┬──────────────────────────────────────────────────────────────────────────
                                                                          │ Welcome to utop version 2.2.0 (using OCaml version 4.07.0)! │                                                                          
                                                                          └─────────────────────────────────────────────────────────────┘                                                                          
Findlib has been successfully loaded. Additional directives:
  #require "package";;      to load a package
  #list;;                   to list the available packages
  #camlp4o;;                to load camlp4 (standard syntax)
  #camlp4r;;                to load camlp4 (revised syntax)
  #predicates "p,q,...";;   to set these predicates
  Topfind.reset();;         to force that packages will be reloaded
  #thread;;                 to enable threads


Type #utop_help for help about using utop.

─( 12:25:11 )─< command 0 >─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────{ counter: 0 }─
utop # B64.decode ~pad:true "1US3OYAgsVtMvQf36C+oQ8TAI4C86qn2AGAxwjSI5TvF9IvhOqXD5KUHOZxTqyfrKwzc6bt3xSnG7zxWSax2HHxqxKCRU9zyIu1u5nx3zBHo8Giu5WDs5KZLwAXGVyUBxVz2lrW8WsVZXbSuaiDO5Q+6v5C1h1nfp1pS2NfCLu/GfdMOsad51BFSEorUszD7rrkJTt2YjScXk1LQI2zW+Bi+WdpoQdT6qNmmASqRd7FfEfcavuYmmtqTVgvtM1+Ui1AiEyvej53trIRJ/PN9AszEkepdLxumjAtW8/jDyUnNC7aJA/1cfbeWGxSTfkDa1h2kS7YugtDH5IJ/Yu4gZQ==";;
Fatal error: exception Invalid_argument("Zed_utf8.singleton")
➜  ocaml-base64 git:(master) ✗          

A dune utop on mirage/ocaml-base64#24 can reproduce this bug.

[pmetzger]

@dinosaure I presume you expect this should work because it works in other contexts?

[dinosaure]

Euh yes, a program like utop should not have a Fatal error and just give up. From what I know, this error appear when it tried to print the output string (B64.decode returns a (string, [ Msg of string ]) result, and in this case, an Ok ...).

The string is a random string (and surely an invalid UTF-8 string) but utop should, at least, continue the REPL (and did not try to print the output string).

[pmetzger]

Ah, I didn't get that utop itself was exiting.