flambda-backend: Remove Config.runtime5 check in dll.ml; guard the one in symbol.ml (#2072)

* Harmonize caml_dynlink_open_lib interface between 4 and 5 runtimes

* Add check for running inside ocamlc

Author: mshinwell

bytecomp/dll.ml

@@ -19,13 +19,7 @@ type dll_handle
 type dll_address
 type dll_mode = For_checking | For_execution
 
-external dll_open5: string -> dll_handle = "caml_dynlink_open_lib"
-
-external dll_open4: dll_mode -> string -> dll_handle = "caml_dynlink_open_lib"
-
-let dll_open mode path =
-  if Config.runtime5 then dll_open5 path else dll_open4 mode path
-
+external dll_open: dll_mode -> string -> dll_handle = "caml_dynlink_open_lib"
 external dll_close: dll_handle -> unit = "caml_dynlink_close_lib"
 external dll_sym: dll_handle -> string -> dll_address
                 = "caml_dynlink_lookup_symbol"

driver/maindriver.ml

@@ -19,6 +19,7 @@ open Clflags
 module Options = Main_args.Make_bytecomp_options (Main_args.Default.Main)
 
 let main argv ppf =
+  Symbol.this_is_ocamlc ();
   let program = "ocamlc" in
   Clflags.add_arguments __LOC__ Options.list;
   Clflags.add_arguments __LOC__

runtime/dynlink.c

@@ -235,7 +235,9 @@ void caml_free_shared_libs(void)
 
 #define Handle_val(v) (*((void **) (v)))
 
-CAMLprim value caml_dynlink_open_lib(value filename)
+/* The mode argument is here for compatibility with runtime4. */
+/* CR ocaml 5 runtime: Remove [mode] when all-runtime5. */
+CAMLprim value caml_dynlink_open_lib(value mode, value filename)
 {
   void * handle;
   value result;

utils/symbol.ml

@@ -47,11 +47,17 @@ end)
 
 let caml_symbol_prefix = "caml"
 
+(* CR ocaml 5 runtime: Remove this_is_ocamlc and force_runtime4_symbols once
+   fully on runtime5 *)
+let this_is_ocamlc = ref false
 let force_runtime4_symbols = ref false
 
 let separator () =
+  if !this_is_ocamlc then
+    Misc.fatal_error "Didn't expect utils/symbol.ml to be used in ocamlc";
   if Config.runtime5 && not !force_runtime4_symbols then "." else "__"
 
+let this_is_ocamlc () = this_is_ocamlc := true
 let force_runtime4_symbols () = force_runtime4_symbols := true
 
 let linkage_name t = t.linkage_name

utils/symbol.mli

@@ -49,3 +49,6 @@ val is_predef_exn : t -> bool
 (* Temporary means by which to force symbol names to use __.  Only for use
    for flambda2 flexpect tests. *)
 val force_runtime4_symbols : unit -> unit
+
+(* Temporary means to identify that the program running is ocamlc. *)
+val this_is_ocamlc : unit -> unit