Extract arch and os from machine triplet when available, add machine triplet variable.

src/core/opamStd.ml

@@ -987,19 +987,31 @@ module OpamSys = struct
 
   let etc () = "/etc"
 
-  let uname =
+  let get_process name =
     let memo = Hashtbl.create 7 in
     fun arg ->
       try Hashtbl.find memo arg with Not_found ->
         let r =
           try
-            with_process_in "uname" arg
+            with_process_in name arg
               (fun ic -> Some (OpamString.strip (input_line ic)))
           with Unix.Unix_error _ | Sys_error _ | Not_found -> None
         in
         Hashtbl.add memo arg r;
         r
 
+  let uname = get_process "uname"
+  let gcc = get_process "gcc"
+  let clang = get_process "clang"
+
+  let machine_triplet =
+    let machine_triplet = lazy (
+      match gcc "-dumpmachine" with
+      | None -> clang "-dumpmachine"
+      | v -> v
+    ) in
+    fun () -> Lazy.force machine_triplet
+
   let system () =
     (* CSIDL_SYSTEM = 0x25 *)
     OpamStubs.(shGetFolderPath 0x25 SHGFP_TYPE_CURRENT)
@@ -1020,14 +1032,22 @@ module OpamSys = struct
     let os = lazy (
       match Sys.os_type with
       | "Unix" -> begin
-          match uname "-s" with
-          | Some "Darwin"    -> Darwin
-          | Some "Linux"     -> Linux
-          | Some "FreeBSD"   -> FreeBSD
-          | Some "OpenBSD"   -> OpenBSD
-          | Some "NetBSD"    -> NetBSD
-          | Some "DragonFly" -> DragonFly
-          | _                -> Unix
+          match machine_triplet () with
+          | Some s when OpamString.contains ~sub:"darwin" s -> Darwin
+          | Some s when OpamString.contains ~sub:"linux" s -> Linux
+          | Some s when OpamString.contains ~sub:"freebsd" s -> FreeBSD
+          | Some s when OpamString.contains ~sub:"openbsd" s -> OpenBSD
+          | Some s when OpamString.contains ~sub:"netbsd" s -> NetBSD
+          | Some s when OpamString.contains ~sub:"dragonfly" s -> DragonFly
+          | _ -> (
+              match uname "-s" with
+              | Some "Darwin"    -> Darwin
+              | Some "Linux"     -> Linux
+              | Some "FreeBSD"   -> FreeBSD
+              | Some "OpenBSD"   -> OpenBSD
+              | Some "NetBSD"    -> NetBSD
+              | Some "DragonFly" -> DragonFly
+              | _                -> Unix)
         end
       | "Win32"  -> Win32
       | "Cygwin" -> Cygwin

src/core/opamStd.mli

@@ -494,6 +494,9 @@ module Sys : sig
           | Unix
           | Other of string
 
+  (** Machine triplet, if found. Queried lazily. *)
+  val machine_triplet : unit -> string option
+
   (** Queried lazily *)
   val os: unit -> os
 

src/state/opamSysPoll.ml

@@ -35,7 +35,11 @@ let normalise_arch raw =
 
 let poll_arch () =
   let raw = match Sys.os_type with
-    | "Unix" | "Cygwin" -> OpamStd.Sys.uname "-m"
+    | "Unix" | "Cygwin" ->
+      begin match Option.map (String.split_on_char '-') (OpamStd.Sys.machine_triplet ()) with
+      | Some (arch::_) -> Some arch
+      | _ -> OpamStd.Sys.uname "-m"
+      end
     | "Win32" ->
       begin match OpamStubs.getArchitecture () with
       | OpamStubs.AMD64 -> Some "x86_64"
@@ -171,6 +175,7 @@ let variables =
       "os-distribution", os_distribution;
       "os-version", os_version;
       "os-family", os_family;
+      "machine-triplet", lazy (OpamStd.Sys.machine_triplet ());
     ]
 
 let cores =