d-form fails with a Cstruct.blit_from_string error

[edwintorok]

As soon as I submit something simple like 'a':

~/example/d-form % dune exec ./form.exe
14.05.21 15:55:15.327                       Running on http://localhost:8080
14.05.21 15:55:15.327                       Press ENTER to stop
14.05.21 15:55:23.131       dream.log  INFO REQ 1 GET / 127.0.0.1:41998 Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:88.0) Gecko/20100101 Firefox/88.0
14.05.21 15:55:23.131       dream.log  INFO REQ 1 200 in 152 μs
14.05.21 15:55:25.484       dream.log  INFO REQ 2 POST / 127.0.0.1:41998 Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:88.0) Gecko/20100101 Firefox/88.0
14.05.21 15:55:25.484       dream.log  WARN REQ 2 Aborted by: Invalid_argument("Cstruct.blit_from_string src=[81] dst=[0,81](81) src-off=13 len=81")
14.05.21 15:55:25.484      dream.http ERROR Invalid_argument("Cstruct.blit_from_string src=[81] dst=[0,81](81) src-off=13 len=81")
14.05.21 15:55:25.484      dream.http ERROR Raised at file "stdlib.ml", line 30, characters 20-45
14.05.21 15:55:25.484      dream.http ERROR Called from file "lib/cstruct.ml", line 407, characters 4-30
14.05.21 15:55:25.484      dream.http ERROR Called from file "src/cipher/cipher.ml", line 108, characters 12-50
14.05.21 15:55:25.484      dream.http ERROR Called from file "src/cipher/cipher.ml", line 38, characters 10-60
14.05.21 15:55:25.484      dream.http ERROR Called from file "src/middleware/csrf.ml", line 44, characters 8-63
14.05.21 15:55:25.484      dream.http ERROR Called from file "src/core/lwt.ml", line 2133, characters 16-20
14.05.21 15:55:25.484      dream.http ERROR Re-raised at file "src/middleware/session.ml", line 29, characters 2-91

This is with dream 1.0.0~alpha1 and master too.
http://dream.as/d-form works though

[edwintorok]

I think the problem here is a missing constraint on cstruct. I had version 5.2.0 installed and that failed as above. When upgrading to cstruct 6.0.0 it all works!

[aantron]

The change is probably specifically due to mirage/ocaml-cstruct@a6a9c3f, "Cstruct: default value of ?len in of_string and of_bytes is now Y.length a - off (used to be Y.length a)," which is part of 6.0.0. I've added the constraint. Thanks for the report!