From f4a307852ee6251a0d53968e7a02452d5693f297 Mon Sep 17 00:00:00 2001
From: Sabine Schmaltz <sabineschmaltz@gmail.com>
Date: Tue, 25 Jul 2023 09:20:23 +0200
Subject: [PATCH] WIP: Attempt to fix Cmi_format error in voodoo-do, by
 checking in prep that the magic numbers are ok #115 (58ec9ae)

---
 src/voodoo-prep/prep.ml | 36 ++++++++++++++++++++++++++++++++----
 1 file changed, 32 insertions(+), 4 deletions(-)

diff --git a/src/voodoo-prep/prep.ml b/src/voodoo-prep/prep.ml
index 0d1be66e..43a7aca6 100644
--- a/src/voodoo-prep/prep.ml
+++ b/src/voodoo-prep/prep.ml
@@ -12,10 +12,37 @@ let process_package : Fpath.t -> Package.t -> Fpath.t list -> unit =
  fun root package files ->
   let dest = Package.prep_path package in
 
+  let format_matches_compiler_version path =
+    let open Unix in
+    let cmd = "ocamlobjinfo " ^ Fpath.to_string path in
+    try
+      let ic, oc = open_process cmd in
+      let rec matches_version ic =
+        try
+          let line = input_line ic in
+          let prefix = "Wrong magic number" in
+          let str_len = String.length line in
+          if str_len >= 18 && String.sub line 0 18 = prefix then (
+            Printf.eprintf "ERROR: ocamlobjinfo on %s: %s\n"
+              (Fpath.to_string path) line;
+            false)
+          else if str_len > 0 then matches_version ic
+          else true
+        with End_of_file -> true
+      in
+      let matches_version = matches_version ic in
+      let _ = close_process (ic, oc) in
+      matches_version
+    with _ ->
+      Printf.eprintf "ERROR: Failed to run ocamlobjinfo on %s\n"
+        (Fpath.to_string path);
+      false
+  in
+
   (* Some packages produce ocaml artefacts that can't be processed with the switch's
       ocaml compiler - most notably the secondary compiler! This switch is intended to
       be used to ignore those files *)
-  let process_ocaml_artefacts =
+  let is_blacklisted =
     let package_blacklist = [ "ocaml-secondary-compiler" ] in
     not (List.mem package.name package_blacklist)
   in
@@ -33,16 +60,17 @@ let process_package : Fpath.t -> Package.t -> Fpath.t list -> unit =
     let no_ext = Fpath.rem_ext filename in
     let has_hyphen = String.contains (Fpath.to_string filename) '-' in
     let is_module =
-      process_ocaml_artefacts
+      not is_blacklisted
       && List.mem ext [ ".cmt"; ".cmti"; ".cmi" ]
-      && not has_hyphen
+      && (not has_hyphen)
+      && format_matches_compiler_version Fpath.(root // fpath)
     in
     let do_copy =
       (not in_build_dir)
       && (is_in_doc_dir || is_module
          || List.mem no_ext (List.map Fpath.v [ "META"; "dune-package" ]))
     in
-    let is_cma = process_ocaml_artefacts && List.mem ext [ ".cma"; ".cmxa" ] in
+    let is_cma =  not is_blacklisted && List.mem ext [ ".cma"; ".cmxa" ] in
     let copy =
       if do_copy then Fpath.(root // fpath, dest // fpath) :: acc.copy
       else acc.copy