Do not build and install shared libs when not supported (#1165)

Read `ocamlc -where`/Makefile.config to determine whether this is
supported.

Signed-off-by: Jeremie Dimino <jeremie@dimino.org>

CHANGES.md

@@ -21,6 +21,9 @@ next
 
 - Highlight multi-line errors (#1131, @anuragsoni)
 
+- Do no try to generate shared libraries when this is not supported by
+  the OS (#1165, fix #1051, @diml)
+
 1.1.1 (08/08/2018)
 ------------------
 

src/context.ml

@@ -47,7 +47,7 @@ type t =
   ; findlib_toolchain       : string option
   ; arch_sixtyfour          : bool
   ; opam_var_cache          : (string, string) Hashtbl.t
-  ; natdynlink_supported    : bool
+  ; natdynlink_supported    : Dynlink_supported.By_the_os.t
   ; ocaml_config            : Ocaml_config.t
   ; version_string          : string
   ; version                 : Ocaml_version.t
@@ -81,6 +81,7 @@ type t =
   ; ast_intf_magic_number   : string
   ; cmxs_magic_number       : string
   ; cmt_magic_number        : string
+  ; supports_shared_libraries : Dynlink_supported.By_the_os.t
   ; which_cache             : (string, Path.t option) Hashtbl.t
   }
 
@@ -104,7 +105,10 @@ let sexp_of_t t =
     ; "env", Env.sexp_of_t (Env.diff t.env Env.initial)
     ; "findlib_path", list path (Findlib.path t.findlib)
     ; "arch_sixtyfour", bool t.arch_sixtyfour
-    ; "natdynlink_supported", bool t.natdynlink_supported
+    ; "natdynlink_supported",
+      bool (Dynlink_supported.By_the_os.get t.natdynlink_supported)
+    ; "supports_shared_libraries",
+      bool (Dynlink_supported.By_the_os.get t.supports_shared_libraries)
     ; "opam_vars", string_hashtbl string t.opam_var_cache
     ; "ocaml_config", Ocaml_config.sexp_of_t t.ocaml_config
     ; "which", string_hashtbl (option path) t.which_cache
@@ -260,19 +264,22 @@ let create ~(kind : Kind.t) ~path ~env ~env_nodes ~name ~merlin ~targets
     in
     let ocaml_config_ok_exn = function
       | Ok x -> x
-      | Error msg ->
+      | Error (Ocaml_config.Origin.Ocamlc_config, msg) ->
         die "Failed to parse the output of '%s -config':@\n\
              %s"
           (Path.to_string ocamlc) msg
+      | Error (Makefile_config file, msg) ->
+        Loc.fail (Loc.in_file (Path.to_string file)) "%s" msg
     in
     Fiber.fork_and_join
       findlib_path
       (fun () ->
          Process.run_capture_lines ~env Strict ocamlc ["-config"]
          >>| fun lines ->
-         let open Result.O in
          ocaml_config_ok_exn
-           (Ocaml_config.Vars.of_lines lines >>= Ocaml_config.make))
+           (match Ocaml_config.Vars.of_lines lines with
+            | Ok vars -> Ocaml_config.make vars
+            | Error msg -> Error (Ocamlc_config, msg)))
     >>= fun (findlib_path, ocfg) ->
     let version = Ocaml_version.of_ocaml_config ocfg in
     let env =
@@ -368,7 +375,8 @@ let create ~(kind : Kind.t) ~path ~env ~env_nodes ~name ~merlin ~targets
 
       ; opam_var_cache
 
-      ; natdynlink_supported
+      ; natdynlink_supported =
+          Dynlink_supported.By_the_os.of_bool natdynlink_supported
 
       ; stdlib_dir
       ; ocaml_config = ocfg
@@ -403,6 +411,9 @@ let create ~(kind : Kind.t) ~path ~env ~env_nodes ~name ~merlin ~targets
       ; ast_intf_magic_number   = Ocaml_config.ast_intf_magic_number   ocfg
       ; cmxs_magic_number       = Ocaml_config.cmxs_magic_number       ocfg
       ; cmt_magic_number        = Ocaml_config.cmt_magic_number        ocfg
+      ; supports_shared_libraries =
+          Dynlink_supported.By_the_os.of_bool
+            (Ocaml_config.supports_shared_libraries ocfg)
 
       ; which_cache
       }

src/context.mli

@@ -86,7 +86,7 @@ type t =
   ; opam_var_cache : (string, string) Hashtbl.t
 
   ; (** Native dynlink *)
-    natdynlink_supported : bool
+    natdynlink_supported : Dynlink_supported.By_the_os.t
 
   ; ocaml_config            : Ocaml_config.t
   ; version_string          : string
@@ -122,6 +122,8 @@ type t =
   ; cmxs_magic_number       : string
   ; cmt_magic_number        : string
 
+  ; supports_shared_libraries : Dynlink_supported.By_the_os.t
+
   ; which_cache             : (string, Path.t option) Hashtbl.t
   }
 

src/dune_file.ml

@@ -913,7 +913,7 @@ module Library = struct
     ; wrapped                  : bool
     ; optional                 : bool
     ; buildable                : Buildable.t
-    ; dynlink                  : bool
+    ; dynlink                  : Dynlink_supported.t
     ; project                  : Dune_project.t
     ; sub_systems              : Sub_system_info.t Sub_system_name.Map.t
     ; no_keep_locs             : bool
@@ -999,7 +999,7 @@ module Library = struct
        ; wrapped
        ; optional
        ; buildable
-       ; dynlink = not no_dynlink
+       ; dynlink = Dynlink_supported.of_bool (not no_dynlink)
        ; project
        ; sub_systems
        ; no_keep_locs

src/dune_file.mli

@@ -226,7 +226,7 @@ module Library : sig
     ; wrapped                  : bool
     ; optional                 : bool
     ; buildable                : Buildable.t
-    ; dynlink                  : bool
+    ; dynlink                  : Dynlink_supported.t
     ; project                  : Dune_project.t
     ; sub_systems              : Sub_system_info.t Sub_system_name.Map.t
     ; no_keep_locs             : bool

src/dynlink_supported.ml

@@ -0,0 +1,9 @@
+module By_the_os = struct
+  type t = bool
+  let of_bool t = t
+  let get t = t
+end
+
+type t = bool
+let of_bool t = t
+let get x y = x && y

src/dynlink_supported.mli

@@ -0,0 +1,11 @@
+(** Track whether dynamic loading of code is supported *)
+
+module By_the_os : sig
+  type t
+  val of_bool : bool -> t
+  val get : t -> bool
+end
+
+type t
+val of_bool : bool -> t
+val get : t -> By_the_os.t -> bool

src/install_rules.ml

@@ -168,7 +168,7 @@ module Gen(P : Params) = struct
                ; Library.archive ~dir lib ~ext:ctx.ext_lib
                ]
              in
-             if ctx.natdynlink_supported && lib.dynlink then
+             if Dynlink_supported.get lib.dynlink ctx.natdynlink_supported then
                files @ [ Library.archive ~dir lib ~ext:".cmxs" ]
              else
                files)
@@ -178,7 +178,8 @@ module Gen(P : Params) = struct
         ]
     in
     let dlls  =
-      if_ (byte && Library.has_stubs lib && lib.dynlink)
+      if_ (byte && Library.has_stubs lib &&
+           Dynlink_supported.get lib.dynlink ctx.supports_shared_libraries)
         [Library.dll ~dir lib ~ext_dll:ctx.ext_dll]
     in
     let execs =

src/lib_rules.ml

@@ -196,7 +196,7 @@ module Gen (P : Install_rules.Params) = struct
     let ocamlmklib = ocamlmklib lib ~scope ~dir ~o_files in
     if modes.native &&
        modes.byte   &&
-       lib.dynlink
+       Dynlink_supported.get lib.dynlink ctx.supports_shared_libraries
     then begin
       (* If we build for both modes and support dynlink, use a
          single invocation to build both the static and dynamic
@@ -340,7 +340,9 @@ module Gen (P : Install_rules.Params) = struct
 
     let dep_graphs = Ocamldep.rules cctx in
 
-    let dynlink = lib.dynlink in
+    let dynlink =
+      Dynlink_supported.get lib.dynlink ctx.supports_shared_libraries
+    in
     let js_of_ocaml = lib.buildable.js_of_ocaml in
     Module_compilation.build_modules cctx ~js_of_ocaml ~dynlink ~dep_graphs;
 
@@ -385,7 +387,7 @@ module Gen (P : Install_rules.Params) = struct
       let target = Path.extend_basename src ~suffix:".js" in
       Js_of_ocaml_rules.build_cm cctx ~js_of_ocaml ~src ~target);
 
-    if ctx.natdynlink_supported then
+    if Dynlink_supported.By_the_os.get ctx.natdynlink_supported then
       build_shared lib ~dir ~flags ~ctx;
 
     Odoc.setup_library_odoc_rules lib ~requires ~modules ~dep_graphs ~scope;

src/ocaml-config/ocaml_config.ml

@@ -82,6 +82,7 @@ type t =
   ; cmxs_magic_number        : string
   ; cmt_magic_number         : string
   ; natdynlink_supported     : bool
+  ; supports_shared_libraries : bool
   }
 
 let version                  t = t.version
@@ -131,6 +132,7 @@ let ast_intf_magic_number    t = t.ast_intf_magic_number
 let cmxs_magic_number        t = t.cmxs_magic_number
 let cmt_magic_number         t = t.cmt_magic_number
 let natdynlink_supported     t = t.natdynlink_supported
+let supports_shared_libraries t = t.supports_shared_libraries
 
 let to_list t : (string * Value.t) list =
   [ "version"                  , String        t.version_string
@@ -179,6 +181,7 @@ let to_list t : (string * Value.t) list =
   ; "cmxs_magic_number"        , String        t.cmxs_magic_number
   ; "cmt_magic_number"         , String        t.cmt_magic_number
   ; "natdynlink_supported"     , Bool          t.natdynlink_supported
+  ; "supports_shared_libraries", Bool          t.supports_shared_libraries
   ]
 
 let sexp_of_t t =
@@ -189,9 +192,11 @@ let sexp_of_t t =
                   ; Value.sexp_of_t v
                   ]))
 
-exception E of string
-let fail fmt =
-  Printf.ksprintf (fun msg -> raise (E msg)) fmt
+module Origin = struct
+  type t =
+    | Ocamlc_config
+    | Makefile_config of Path.t
+end
 
 let split_prog s =
   match String.extract_blank_separated_words s with
@@ -209,7 +214,11 @@ module Vars = struct
         | Some i ->
           let x =
             (String.sub line ~pos:0 ~len:i,
-             String.sub line ~pos:(i + 2) ~len:(String.length line - i - 2))
+             let len = String.length line - i - 2 in
+             if len < 0 then
+               ""
+             else
+               String.sub line ~pos:(i + 2) ~len)
           in
           loop (x :: acc) lines
         | None ->
@@ -219,51 +228,71 @@ module Vars = struct
     Result.map_error (String.Map.of_list vars) ~f:(fun (var, _, _) ->
       Printf.sprintf "Variable %S present twice." var)
 
-  let get_opt t var = String.Map.find t var
+  let load_makefile_config file =
+    let lines = Io.lines_of_file file in
+    List.filter_map lines ~f:(fun line ->
+      let line = String.trim line in
+      if line = "" || line.[0] = '#' then
+        None
+      else
+        String.lsplit2 line ~on:'=')
+    |> String.Map.of_list_reduce ~f:(fun _ x -> x)
+
+  exception E of Origin.t * string
 
-  let get t var =
-    match get_opt t var with
-    | Some s -> s
-    | None   -> fail "Variable %S not found." var
+  module Getters(Origin : sig val origin : Origin.t end) = struct
+    let fail fmt =
+      Printf.ksprintf (fun msg -> raise (E (Origin.origin, msg))) fmt
 
-  let get_bool t var =
-    match get_opt t var with
-    | None -> false
-    | Some s ->
-      match s with
-      | "true"  -> true
-      | "false" -> false
-      | s ->
-        fail "Value of %S is neither 'true' neither 'false': %s." var s
+    let get_opt t var = String.Map.find t var
 
-  let get_int_opt t var =
-    match get_opt t var with
-    | None -> None
-    | Some s ->
-      match int_of_string s with
-      | x -> Some x
-      | exception _ ->
-        fail "Value of %S is not an integer: %s." var s
+    let get t var =
+      match get_opt t var with
+      | Some s -> s
+      | None   -> fail "Variable %S not found." var
 
-  let get_words t var =
-    match get_opt t var with
-    | None   -> []
-    | Some s -> String.extract_blank_separated_words s
+    let get_bool t ?(default=false) var =
+      match get_opt t var with
+      | None -> default
+      | Some s ->
+        match s with
+        | "true"  -> true
+        | "false" -> false
+        | s ->
+          fail "Value of %S is neither 'true' neither 'false': %s." var s
 
-  let get_prog_or_dummy t var =
-    Option.map (get_opt t var) ~f:(fun v ->
-      match split_prog v with
-      | None ->
-        { prog = Printf.sprintf "%s-not-found-in-ocaml-config" var
-        ; args = []
-        }
+    let get_int_opt t var =
+      match get_opt t var with
+      | None -> None
+      | Some s ->
+        match int_of_string s with
+        | x -> Some x
+        | exception _ ->
+          fail "Value of %S is not an integer: %s." var s
+
+    let get_words t var =
+      match get_opt t var with
+      | None   -> []
+      | Some s -> String.extract_blank_separated_words s
+
+    let get_prog_or_dummy t var =
+      Option.map (get_opt t var) ~f:(fun v ->
+        match split_prog v with
+        | None ->
+          { prog = Printf.sprintf "%s-not-found-in-ocaml-config" var
+          ; args = []
+          }
+        | Some s -> s
+      )
+
+    let get_prog_or_dummy_exn t var =
+      match get_prog_or_dummy t var with
+      | None -> fail "Variable %S not found." var
       | Some s -> s
-    )
+  end
 
-  let get_prog_or_dummy_exn t var =
-    match get_prog_or_dummy t var with
-    | None -> fail "Variable %S not found." var
-    | Some s -> s
+  module Ocamlc_config_getters =
+    Getters(struct let origin = Origin.Ocamlc_config end)
 end
 
 let get_arch_sixtyfour stdlib_dir =
@@ -287,7 +316,7 @@ let get_arch_sixtyfour stdlib_dir =
 
 let make vars =
   match
-    let open Vars in
+    let open Vars.Ocamlc_config_getters in
     let bytecomp_c_compiler =
       get_prog_or_dummy_exn vars "bytecomp_c_compiler" in
     let native_c_compiler =
@@ -369,6 +398,15 @@ let make vars =
     let natdynlink_supported =
       Sys.file_exists (Filename.concat standard_library "dynlink.cmxa")
     in
+
+    let file =
+      Path.relative (Path.of_string standard_library) "Makefile.config"
+    in
+    let vars = Vars.load_makefile_config file in
+    let module Getters =
+      Vars.Getters(struct let origin = Origin.Makefile_config file end)
+    in
+    let supports_shared_libraries = get_bool vars "SUPPORTS_SHARED_LIBRARIES" in
     { version
     ; version_string
     ; standard_library_default
@@ -416,7 +454,8 @@ let make vars =
     ; cmxs_magic_number
     ; cmt_magic_number
     ; natdynlink_supported
+    ; supports_shared_libraries
     }
   with
-  | t                 -> Ok t
-  | exception (E msg) -> Error msg
+  | t -> Ok t
+  | exception (Vars.E (origin, msg)) -> Error (origin, msg)