Rework solver version detection, still under some assumptions.

solver.ml

@@ -57,7 +57,7 @@ let default_exe_name_of_solver = function
   | Marabou -> "Marabou"
 
 let default_option_of_solver = function
-  | Pyrat -> "--version"
+  | Pyrat -> "-v"
   | Marabou -> "--version"
 
 let exe_path_of_solver solver =
@@ -122,6 +122,8 @@ let version_of_solver solver s =
   in
   let regexp_version = Str.regexp regexp_string in
   try
+    (* We suppose that the first occurrence that matches [regexp_string] is
+       indeed the version of the concercend [solver]. *)
     ignore (Str.search_forward regexp_version s 0);
     Version (Str.matched_string s)
   with Stdlib.Not_found ->
@@ -204,9 +206,18 @@ let detect_default_solvers () =
               (fun m -> m "Executing command `%s' to detect `%a'."
                   cmd pp_solver solver);
             let retcode = Sys.command cmd in
-            let in_channel = Stdlib.open_in tmp in
-            let firstline = Stdlib.input_line in_channel in
-            Stdlib.close_in in_channel;
+            let cmd_output =
+              let in_channel = Stdlib.open_in tmp in
+              let buf = Buffer.create 512 in
+              try
+                while true do
+                  Stdlib.Buffer.add_channel buf in_channel 512;
+                done;
+                assert false
+              with End_of_file ->
+                Stdlib.close_in in_channel;
+                Buffer.contents buf
+            in
             Sys.remove tmp;
             if retcode <> 0
             then begin
@@ -215,7 +226,7 @@ let detect_default_solvers () =
             end
             else begin
               (* If available, we save a [config] for solver. *)
-              let version = version_of_solver solver firstline in
+              let version = version_of_solver solver cmd_output in
               let config = { solver; exe; version; } in
               Logs.app
                 (fun m -> m "Found solver `%a' `%a' (%s)."