error.txt

2/5: Building Libgit.FFI (src/Libgit/FFI.idr)
src/Libgit/FFI.idr:30:24--35:11:Can't marshal type for foreign call (Libgit.FFI.case block in byteLengthToType Libgit.FFI.prim_int_size_bytes) at:
30      byteLengthToType len = case len of
31        1 => Bits8
32        2 => Bits16
33        4 => Bits32
34        8 => Bits64
35        _ => Int

FFIExample.idr

module FFIExample

import System.FFI

-- System info helpers

export
%foreign "C:int_size_bytes,shim"
prim_int_size_bytes : Int

export
%foreign "C:size_t_size_bytes,shim"
prim_size_t_size_bytes : Int

-- I don't love this, but without providers I don't have a mechanism to fail at
-- compile time, so I'll default to Int which doesn't seem so harmful. Famous
-- last words?
byteLengthToType : Bits8 -> Type
byteLengthToType len = case len of
  1 => Bits8
  2 => Bits16
  4 => Bits32
  8 => Bits64
  _ => Int

CUInt : Num a => (a : Type)
CUInt = byteLengthToType prim_int_size_bytes

CSizeT : Num a => (a : Type)
CSizeT = byteLengthToType prim_size_t_size_bytes

shim.c

uint8_t int_size_bytes() {
  return sizeof(int);
}

uint8_t size_t_size_bytes() {
  return sizeof(size_t);
}