On 2015-09-23 14:23, Alan Schmitt <alan.schmitt@polytechnique.org> writes:

> Is there a guide somewhere that explains how to create a new opam switch
> From local (modified) ocaml sources?

A very helpful colleague gave me a crash course on nix and I was able to
compile a patched version (where I tweaked error_of_printer in
parsing/location.ml as follows):

#+begin_src ocaml
let error_of_printer loc print x =
  let buf = Buffer.create 64 in
  let ppf = Format.formatter_of_buffer buf in
  Format.pp_set_margin ppf (Format.pp_get_margin !formatter_for_warnings ());
  pp_print_string ppf "Error: ";
  print ppf x;
  pp_print_flush ppf ();
  let msg = Buffer.contents buf in
  errorf ~loc "%s" msg
#+end_src

This works great: I can now change the margin of the error messages
simply by doing a "Format.set_margin" in the toplevel.

Alan

-- 
OpenPGP Key ID : 040D0A3B4ED2E5C7
Athmospheric CO₂ (Updated September 22, 2015, Mauna Loa Obs.): 397.77 ppm