diff --git a/Lama.opam b/Lama.opam
index 9c4ef486f..18a1e98f2 100644
--- a/Lama.opam
+++ b/Lama.opam
@@ -17,6 +17,7 @@ depends: [
   "camlp5"      { >= "8.00.05" }
   "ostap"       { >= "0.5"}
   "GT"          { >= "0.5.1" }
+  "posix-uname" {  = "2.0.2" }
 ]
 
 build: [
diff --git a/regression/Makefile b/regression/Makefile
index f74f736bd..0ac335344 100644
--- a/regression/Makefile
+++ b/regression/Makefile
@@ -3,6 +3,13 @@ TESTS=$(sort $(filter-out test111, $(basename $(wildcard test*.lama))))
 
 LAMAC=../src/lamac
 
+UNAME_S := $(shell uname -s)
+
+ifeq ($(UNAME_S),Linux)
+else ifeq ($(UNAME_S),Darwin)
+    ARCH = arch -x86_64
+endif
+
 .PHONY: check $(TESTS)
 
 
@@ -12,11 +19,11 @@ $(TESTS): %: %.lama
 	@echo "regression/$@"
 # @cat $@.input | LAMA=../runtime $(LAMAC) -i $< > $@.log && diff $@.log orig/$@.log
 # @cat $@.input | LAMA=../runtime $(LAMAC) -ds -s $< > $@.log && diff $@.log orig/$@.log
-	@LAMA=../runtime $(LAMAC) $< && cat $@.input | arch -x86_64 ./$@ > $@.log && diff $@.log orig/$@.log
+	@LAMA=../runtime $(LAMAC) $< && cat $@.input | $(ARCH) ./$@ > $@.log && diff $@.log orig/$@.log
 
 ctest111:
 	@echo "regression/test111"
-	@LAMA=../runtime $(LAMAC) test111.lama && cat test111.input | arch -x86_64 ./test111 > test111.log && diff test111.log orig/test111.log
+	@LAMA=../runtime $(LAMAC) test111.lama && cat test111.input | $(ARCH) ./test111 > test111.log && diff test111.log orig/test111.log
 
 clean:
 	$(RM) test*.log *.s *.sm *~ $(TESTS) *.i $(DEBUG_FILES) test111
diff --git a/runtime/Makefile b/runtime/Makefile
index bc19673cc..b15fbce12 100644
--- a/runtime/Makefile
+++ b/runtime/Makefile
@@ -51,8 +51,8 @@ runtime.o: runtime.c runtime.h
 runtime64.o: runtime.c runtime.h
 	$(CC) $(PROD_FLAGS) -c runtime.c -o runtime64.o
 
-printf.o: printf.s
-	$(CC) $(PROD_FLAGS) -c -g printf.s -o printf.o
+printf.o: printf.S
+	$(CC) $(PROD_FLAGS) -x assembler-with-cpp -c -g printf.S -o printf.o
 
 clean:
 	$(RM) *.a *.o *~ negative_scenarios/*.err
diff --git a/runtime/gc.c b/runtime/gc.c
index 75ef2675e..a9d4d1775 100644
--- a/runtime/gc.c
+++ b/runtime/gc.c
@@ -26,9 +26,13 @@ static extra_roots_pool extra_roots;
 
 size_t __gc_stack_top = 0, __gc_stack_bottom = 0;
 #ifdef LAMA_ENV
+#ifdef __linux__
+extern const size_t __start_custom_data, __stop_custom_data;
+#elif defined(__APPLE__)
 extern const size_t __start_custom_data __asm("section$start$__DATA$custom_data");
 extern const size_t __stop_custom_data __asm("section$end$__DATA$custom_data");
 #endif
+#endif
 
 #ifdef DEBUG_VERSION
 memory_chunk heap;
diff --git a/runtime/printf.s b/runtime/printf.S
similarity index 63%
rename from runtime/printf.s
rename to runtime/printf.S
index ed16ffc4f..046bc8885 100644
--- a/runtime/printf.s
+++ b/runtime/printf.S
@@ -1,22 +1,27 @@
+#ifdef __linux__
+#define PREFIXED(name) name
+#elif defined(__APPLE__)
+#define PREFIXED(name) _##name
+#endif
         .data
 
-        .global _Lprintf
-        .extern _Bprintf
+        .global PREFIXED(Lprintf)
+        .extern PREFIXED(Bprintf)
 
-        .global _Lfprintf
-        .extern _Bfprintf
+        .global PREFIXED(Lfprintf)
+        .extern PREFIXED(Bfprintf)
 
-        .global _Lsprintf
-        .extern _Bsprintf
+        .global PREFIXED(Lsprintf)
+        .extern PREFIXED(Bsprintf)
 
-        .global _Lfailure
-        .extern _failure
+        .global PREFIXED(Lfailure)
+        .extern PREFIXED(failure)
 
         .extern cnt_percentage_sign
 
         .text
 
-_Lprintf:
+PREFIXED(Lprintf):
 # save return address
         popq    %r14
 
@@ -28,22 +33,22 @@ _Lprintf:
         movq    %rsp, %rax
 # rdi --- format string
 # r11 --- number of arguments except format string 
-_Lprintf_loop:
+PREFIXED(Lprintf_loop):
         movq    $0, %r12
         cmpq    %r11, %r12
-        jz    _Lprintf_continue
+        jz    PREFIXED(Lprintf_continue)
 
         decq    %r11
         movq    (%rax), %r10
         testq   $1, %r10
-        jz    _Lprintf_loop_end
+        jz    PREFIXED(Lprintf_loop_end)
 # unbox value
         sarq    %r10
         movq    %r10, (%rax)
-_Lprintf_loop_end:
+PREFIXED(Lprintf_loop_end):
         addq    $8, %rax
-        jmp     _Lprintf_loop
-_Lprintf_continue:
+        jmp     PREFIXED(Lprintf_loop)
+PREFIXED(Lprintf_continue):
         popq    %rsi
         popq    %rdx
         popq    %rcx
@@ -51,9 +56,9 @@ _Lprintf_continue:
         popq    %r9
 # restore return address
         pushq   %r14
-        jmp     _Bprintf
+        jmp     PREFIXED(Bprintf)
 
-_Lfprintf:
+PREFIXED(Lfprintf):
 # save return address
         popq    %r14
 
@@ -65,31 +70,31 @@ _Lfprintf:
 # rdi --- FILE*
 # rsi --- format string
 # r11 --- number of arguments except format string 
-_Lfprintf_loop:
+PREFIXED(Lfprintf_loop):
         movq    $0, %r12
         cmpq    %r11, %r12
-        jz    _Lfprintf_continue
+        jz    PREFIXED(Lfprintf_continue)
 
         decq    %r11
         movq    (%rax), %r10
         testq   $1, %r10
-        jz    _Lfprintf_loop_end
+        jz    PREFIXED(Lfprintf_loop_end)
 # unbox value
         sarq    %r10
         movq    %r10, (%rax)
-_Lfprintf_loop_end:
+PREFIXED(Lfprintf_loop_end):
         addq    $8, %rax
-        jmp     _Lfprintf_loop
-_Lfprintf_continue:
+        jmp     PREFIXED(Lfprintf_loop)
+PREFIXED(Lfprintf_continue):
         popq    %rdx
         popq    %rcx
         popq    %r8
         popq    %r9
 # restore return address
         pushq   %r14
-        jmp     _Bfprintf
+        jmp     PREFIXED(Bfprintf)
 
-_Lsprintf:
+PREFIXED(Lsprintf):
 # save return address
         popq    %r14
 
@@ -101,22 +106,22 @@ _Lsprintf:
         movq    %rsp, %rax
 # rdi --- format string
 # r11 --- number of arguments except format string 
-_Lsprintf_loop:
+PREFIXED(Lsprintf_loop):
         movq    $0, %r12
         cmpq    %r11, %r12
-        jz    _Lsprintf_continue
+        jz    PREFIXED(Lsprintf_continue)
 
         decq    %r11
         movq    (%rax), %r10
         testq   $1, %r10
-        jz    _Lsprintf_loop_end
+        jz    PREFIXED(Lsprintf_loop_end)
 # unbox value
         sarq    %r10
         movq    %r10, (%rax)
-_Lsprintf_loop_end:
+PREFIXED(Lsprintf_loop_end):
         addq    $8, %rax
-        jmp     _Lsprintf_loop
-_Lsprintf_continue:
+        jmp     PREFIXED(Lsprintf_loop)
+PREFIXED(Lsprintf_continue):
         popq    %rsi
         popq    %rdx
         popq    %rcx
@@ -124,9 +129,9 @@ _Lsprintf_continue:
         popq    %r9
 # restore return address
         pushq   %r14
-        jmp     _Bsprintf
+        jmp     PREFIXED(Bsprintf)
 
-_Lfailure:
+PREFIXED(Lfailure):
 # save return address
         popq    %r14
 
@@ -138,22 +143,22 @@ _Lfailure:
         movq    %rsp, %rax
 # rdi --- format string
 # r11 --- number of arguments except format string 
-_Lfailure_loop:
+PREFIXED(Lfailure_loop):
         movq    $0, %r12
         cmpq    %r11, %r12
-        jz    _Lfailure_continue
+        jz    PREFIXED(Lfailure_continue)
 
         decq    %r11
         movq    (%rax), %r10
         testq   $1, %r10
-        jz    _Lfailure_loop_end
+        jz    PREFIXED(Lfailure_loop_end)
 # unbox value
         sarq    %r10
         movq    %r10, (%rax)
-_Lfailure_loop_end:
+PREFIXED(Lfailure_loop_end):
         addq    $8, %rax
-        jmp     _Lfailure_loop
-_Lfailure_continue:
+        jmp     PREFIXED(Lfailure_loop)
+PREFIXED(Lfailure_continue):
         popq    %rsi
         popq    %rdx
         popq    %rcx
@@ -161,4 +166,4 @@ _Lfailure_continue:
         popq    %r9
 # restore return address
         pushq   %r14
-        jmp     _failure
+        jmp     PREFIXED(failure)
diff --git a/src/Driver.ml b/src/Driver.ml
index 64a456abe..ee147f3c2 100644
--- a/src/Driver.ml
+++ b/src/Driver.ml
@@ -143,7 +143,7 @@ class options args =
       Filename.chop_suffix (Filename.basename self#get_infile) ".lama"
 
     method topname =
-      match !mode with `Compile -> "init" ^ self#basename | _ -> "_main"
+      match !mode with `Compile -> "init" ^ self#basename | _ -> "main"
 
     method dump_file ext contents =
       let name = self#basename in
diff --git a/src/SM.ml b/src/SM.ml
index 19ac0d6ca..afef4fa9d 100644
--- a/src/SM.ml
+++ b/src/SM.ml
@@ -14,11 +14,13 @@ type scope = {
 }
 [@@deriving gt ~options:{ show }]
 
-let normal_prefix = "_L"
-let builtin_prefix = "_B"
-let label s = normal_prefix ^ s
-let builtin_label s = builtin_prefix ^ s
-let scope_label i s = label s ^ "_" ^ string_of_int i
+let normal_label = "L"
+let builtin_label = "B"
+let global_label = "global_"
+let labeled s = normal_label ^ s
+let labeled_builtin s = builtin_label ^ s
+let labeled_global s = global_label ^ s
+let labeled_scoped i s = labeled s ^ "_" ^ string_of_int i
 let show_scope = show scope
 
 (* The type for the stack machine instructions *)
@@ -270,13 +272,13 @@ module ByteCode = struct
           add_fixup s;
           add_ints [ 0 ]
       (* 0x70                 *)
-      | CALL (f, _, _) when f = label "read" -> add_bytes [ (7 * 16) + 0 ]
+      | CALL (f, _, _) when f = labeled "read" -> add_bytes [ (7 * 16) + 0 ]
       (* 0x71                 *)
-      | CALL (f, _, _) when f = label "write" -> add_bytes [ (7 * 16) + 1 ]
+      | CALL (f, _, _) when f = labeled "write" -> add_bytes [ (7 * 16) + 1 ]
       (* 0x72                 *)
-      | CALL (f, _, _) when f = label "length" -> add_bytes [ (7 * 16) + 2 ]
+      | CALL (f, _, _) when f = labeled "length" -> add_bytes [ (7 * 16) + 2 ]
       (* 0x73                 *)
-      | CALL (f, _, _) when f = label "string" -> add_bytes [ (7 * 16) + 3 ]
+      | CALL (f, _, _) when f = labeled "string" -> add_bytes [ (7 * 16) + 3 ]
       (* 0x74                 *)
       | CALL (".array", n, _) ->
           add_bytes [ (7 * 16) + 4 ];
@@ -1016,7 +1018,7 @@ class env cmd imports =
       {<funinfo = funinfo#register_closure f self#closure>}
 
     method current_function =
-      match fundefs with Top _ -> "_main" | Item (fd, _, _) -> fd.name
+      match fundefs with Top _ -> "main" | Item (fd, _, _) -> fd.name
 
     method private import_imports =
       let paths = cmd#get_include_paths in
@@ -1037,10 +1039,10 @@ class env cmd imports =
     method global_scope = scope_index = 0
 
     method get_label =
-      (label @@ string_of_int label_index, {<label_index = label_index + 1>})
+      (labeled @@ string_of_int label_index, {<label_index = label_index + 1>})
 
     method get_end_label =
-      let lab = label @@ string_of_int label_index in
+      let lab = labeled @@ string_of_int label_index in
       (lab, {<end_label = lab; label_index = label_index + 1>})
 
     method end_label = end_label
@@ -1048,7 +1050,10 @@ class env cmd imports =
     method nlocals = scope.nlocals
 
     method get_decls =
-      let opt_label = function true -> label | _ -> fun x -> "_global_" ^ x in
+      let opt_label = function
+        | true -> labeled
+        | _ -> labeled_global
+      in
       List.flatten
       @@ List.map (function
            | name, `Extern, f -> [ EXTERN (opt_label f name) ]
@@ -1196,7 +1201,9 @@ class env cmd imports =
                  }>}
 
     method fun_internal_name (name : string) =
-      (match scope.st with State.G _ -> label | _ -> scope_label scope_index)
+      (match scope.st with
+      | State.G _ -> labeled
+      | _ -> labeled_scoped scope_index)
         name
 
     method add_fun_name (name : string)
@@ -1651,7 +1658,7 @@ let compile cmd ((imports, _), p) =
           LABEL topname;
           BEGIN
             ( topname,
-              (if topname = "_main" then 2 else 0),
+              (if topname = "main" then 2 else 0),
               env#nlocals,
               [],
               [],
diff --git a/src/X86.ml b/src/X86.ml
index 605548118..e91ab475e 100644
--- a/src/X86.ml
+++ b/src/X86.ml
@@ -4,6 +4,18 @@ open SM
 
 (* X86 codegeneration interface *)
 
+type os_t = Linux | Darwin
+
+let os =
+  let uname = Posix_uname.uname () in
+  match uname.sysname with
+  | "Darwin" -> Darwin
+  | "Linux" -> Linux
+  | _ -> failwith "Unsupported OS"
+
+let prefix = match os with Linux -> "" | Darwin -> "_"
+let prefixed name = prefix ^ name
+
 module Register : sig
   type t
 
@@ -203,10 +215,10 @@ let show instr =
     | S i ->
         if i >= 0 then Printf.sprintf "-%d(%%rbp)" (stack_offset i)
         else Printf.sprintf "%d(%%rbp)" (stack_offset i)
-    | M (_, I, _, s) -> Printf.sprintf "%s(%%rip)" s
-    | M (F, E, _, s) -> Printf.sprintf "%s(%%rip)" s
-    | M (D, E, _, s) -> Printf.sprintf "%s@GOTPCREL(%%rip)" s
-    | C s -> Printf.sprintf "$%s" s
+    | M (_, I, _, s) -> Printf.sprintf "%s(%%rip)" (prefixed s)
+    | M (F, E, _, s) -> Printf.sprintf "%s(%%rip)" (prefixed s)
+    | M (D, E, _, s) -> Printf.sprintf "%s@GOTPCREL(%%rip)" (prefixed s)
+    | C s -> Printf.sprintf "$%s" (prefixed s)
     | L i -> Printf.sprintf "$%d" i
     | I (0, x) -> Printf.sprintf "(%s)" (opnd x)
     | I (n, x) -> Printf.sprintf "%d(%s)" n (opnd x)
@@ -237,12 +249,12 @@ let show instr =
   | Push s -> Printf.sprintf "\tpushq\t%s" (opnd s)
   | Pop s -> Printf.sprintf "\tpopq\t%s" (opnd s)
   | Ret -> "\tret"
-  | Call p -> Printf.sprintf "\tcall\t%s" p
+  | Call p -> Printf.sprintf "\tcall\t%s" (prefixed p)
   | CallI o -> Printf.sprintf "\tcall\t*(%s)" (opnd o)
-  | Label l -> Printf.sprintf "%s:\n" l
-  | Jmp l -> Printf.sprintf "\tjmp\t%s" l
+  | Label l -> Printf.sprintf "%s:\n" (prefixed l)
+  | Jmp l -> Printf.sprintf "\tjmp\t%s" (prefixed l)
   | JmpI o -> Printf.sprintf "\tjmp\t*(%s)" (opnd o)
-  | CJmp (s, l) -> Printf.sprintf "\tj%s\t%s" s l
+  | CJmp (s, l) -> Printf.sprintf "\tj%s\t%s" s (prefixed l)
   | Meta s -> Printf.sprintf "%s\n" s
   | Dec s -> Printf.sprintf "\tdecq\t%s" (opnd s)
   | Or1 s -> Printf.sprintf "\torq\t$0x0001,\t%s" (opnd s)
@@ -407,29 +419,29 @@ let compile_binop env op =
 
 let safepoint_functions =
   [
-    label "s__Infix_58";
-    label "substring";
-    label "clone";
-    builtin_label "string";
-    label "stringcat";
-    label "string";
-    builtin_label "closure";
-    builtin_label "array";
-    builtin_label "sexp";
-    label "i__Infix_4343"
+    labeled "s__Infix_58";
+    labeled "substring";
+    labeled "clone";
+    labeled_builtin "string";
+    labeled "stringcat";
+    labeled "string";
+    labeled_builtin "closure";
+    labeled_builtin "array";
+    labeled_builtin "sexp";
+    labeled "i__Infix_4343"
     (* "makeArray"; not required as do not have ptr arguments *)
     (* "makeString"; not required as do not have ptr arguments *)
     (* "getEnv", not required as do not have ptr arguments *)
     (* "set_args", not required as do not have ptr arguments *);
-    (* Lsprintf, or Bsprintf is an extra dirty hack that works? *)
+    (* Lsprintf, or Bsprintf is an extra dirty hack that probably works *)
   ]
 
 let vararg_functions =
   [
-    (label "printf", 1);
-    (label "fprintf", 2);
-    (label "sprintf", 1);
-    (label "failure", 1);
+    (labeled "printf", 1);
+    (labeled "fprintf", 2);
+    (labeled "sprintf", 1);
+    (labeled "failure", 1);
   ]
 
 let compile_call env ?fname nargs tail =
@@ -437,7 +449,7 @@ let compile_call env ?fname nargs tail =
     Option.map
       (fun fname ->
         match fname.[0] with
-        | '.' -> builtin_label (String.sub fname 1 (String.length fname - 1))
+        | '.' -> labeled_builtin (String.sub fname 1 (String.length fname - 1))
         | _ -> fname)
       fname
   in
@@ -557,9 +569,10 @@ let compile_call env ?fname nargs tail =
       let setup_args_code = List.map (fun arg -> Push arg) @@ List.rev args in
       let setup_args_code = setup_args_code @ [ Mov (rsp, rdi) ] in
       let setup_args_code =
-        if fname = builtin_label "closure" then
+        if fname = labeled_builtin "closure" then
           setup_args_code @ [ Mov (L (box (nargs - 1)), rsi) ]
-        else if fname = builtin_label "sexp" || fname = builtin_label "array"
+        else if
+          fname = labeled_builtin "sexp" || fname = labeled_builtin "array"
         then setup_args_code @ [ Mov (L (box nargs), rsi) ]
         else setup_args_code
       in
@@ -715,18 +728,18 @@ let compile cmd env imports code =
                   [ Meta "\t.cfi_startproc" ]
                   @ (if f = cmd#topname then
                        [
-                         Mov (M (D, I, V, "_init"), rax);
+                         Mov (M (D, I, V, "init"), rax);
                          Binop ("test", rax, rax);
-                         CJmp ("z", "_continue");
+                         CJmp ("z", "continue");
                          Ret;
                          Label "_ERROR";
-                         Call (label "binoperror");
+                         Call (labeled "binoperror");
                          Ret;
                          Label "_ERROR2";
-                         Call (label "binoperror2");
+                         Call (labeled "binoperror2");
                          Ret;
-                         Label "_continue";
-                         Mov (L 1, M (D, I, V, "_init"));
+                         Label "continue";
+                         Mov (L 1, M (D, I, V, "init"));
                        ]
                      else [])
                   @ [
@@ -747,21 +760,21 @@ let compile cmd env imports code =
                       Mov (r13, rsi);
                       Mov (r14, rcx);
                     ]
-                  @ (if f = "_main" then
+                  @ (if f = "main" then
                        [
                          (* Align stack as main function is the only function that could be called without alignment. TODO *)
                          Mov (L 0xF, rax);
                          Binop ("test", rsp, rax);
-                         CJmp ("z", "_ALIGNED");
+                         CJmp ("z", "ALIGNED");
                          Push filler;
-                         Label "_ALIGNED";
+                         Label "ALIGNED";
                          (* Initialize gc and arguments *)
                          Push (R Registers.rdi);
                          Push (R Registers.rsi);
-                         Call "___gc_init";
+                         Call "__gc_init";
                          Pop (R Registers.rsi);
                          Pop (R Registers.rdi);
-                         Call "_set_args";
+                         Call "set_args";
                        ]
                      else [])
                   @
@@ -782,7 +795,7 @@ let compile cmd env imports code =
                     Mov (rbp, rsp);
                     Pop rbp;
                   ]
-                  @ (if name = "_main" then [ Binop ("^", rax, rax) ] else [])
+                  @ (if name = "main" then [ Binop ("^", rax, rax) ] else [])
                   @ [
                       Meta "\t.cfi_restore\t5";
                       Meta "\t.cfi_def_cfa\t4, 4";
@@ -791,12 +804,13 @@ let compile cmd env imports code =
                       Meta
                         (* Allocate space for the symbolic stack
                            Add extra word if needed to preserve alignment *)
-                        (Printf.sprintf "\t.set\t%s,\t%d" env#lsize
+                        (Printf.sprintf "\t.set\t%s,\t%d" (prefixed env#lsize)
                            (if env#allocated mod 2 == 0 then
                               env#allocated * word_size
                             else (env#allocated + 1) * word_size));
                       Meta
-                        (Printf.sprintf "\t.set\t%s,\t%d" env#allocated_size
+                        (Printf.sprintf "\t.set\t%s,\t%d"
+                           (prefixed env#allocated_size)
                            env#allocated);
                     ] )
             | RET ->
@@ -1092,7 +1106,7 @@ class env prg =
     method loc x =
       match x with
       | Value.Global name ->
-          let loc_name = "_global_" ^ name in
+          let loc_name = labeled_global name in
           let ext = if self#is_external name then E else I in
           M (D, ext, V, loc_name)
       | Value.Fun name ->
@@ -1146,7 +1160,7 @@ class env prg =
     (* registers a variable in the environment *)
     method variable x =
       match x with
-      | Value.Global name -> {<globals = S.add ("_global_" ^ name) globals>}
+      | Value.Global name -> {<globals = S.add (labeled_global name) globals>}
       | _ -> self
 
     (* registers a string constant *)
@@ -1157,7 +1171,9 @@ class env prg =
         let rec iterate i =
           if i < n then (
             (match x.[i] with
-            | '"'  -> (Buffer.add_char buf '\\'; Buffer.add_char buf '"')
+            | '"' ->
+                Buffer.add_char buf '\\';
+                Buffer.add_char buf '"'
             | c -> Buffer.add_char buf c);
             iterate (i + 1))
         in
@@ -1184,7 +1200,7 @@ class env prg =
 
     (* gets a number of stack positions allocated *)
     method allocated = stack_slots
-    method allocated_size = label (Printf.sprintf "S%s_SIZE" fname)
+    method allocated_size = labeled (Printf.sprintf "S%s_SIZE" fname)
 
     (* enters a function *)
     method enter f nargs nlocals has_closure =
@@ -1197,10 +1213,10 @@ class env prg =
        ; first_line = true>}
 
     (* returns a label for the epilogue *)
-    method epilogue = label (Printf.sprintf "%s_epilogue" fname)
+    method epilogue = labeled (Printf.sprintf "%s_epilogue" fname)
 
     (* returns a name for local size meta-symbol *)
-    method lsize = label (Printf.sprintf "%s_SIZE" fname)
+    method lsize = labeled (Printf.sprintf "%s_SIZE" fname)
 
     (* returns a list of live registers *)
     method live_registers =
@@ -1213,8 +1229,11 @@ class env prg =
     method gen_line =
       let lab = Printf.sprintf ".L%d" nlabels in
       ( {<nlabels = nlabels + 1; first_line = false>},
-        if fname = "_main" then
-          [ (* Meta (Printf.sprintf "\t.stabn 68,0,%d,%s" line lab); *) Label lab ]
+        if fname = "main" then
+          [
+            (* Meta (Printf.sprintf "\t.stabn 68,0,%d,%s" line lab); *)
+            Label lab;
+          ]
         else
           (if first_line then
              [ (* Meta (Printf.sprintf "\t.stabn 68,0,%d,0" line) *) ]
@@ -1232,28 +1251,36 @@ let genasm cmd prog =
   let sm = SM.compile cmd prog in
   let env, code = compile cmd (new env sm) (fst (fst prog)) sm in
   let globals =
-    List.map (fun s -> Meta (Printf.sprintf "\t.globl\t%s" s)) env#publics
+    List.map
+      (fun s -> Meta (Printf.sprintf "\t.globl\t%s" (prefixed s)))
+      env#publics
   in
   let data =
     [ Meta "\t.data" ]
     @ List.map
-        (fun (s, v) -> Meta (Printf.sprintf "%s:\t.string\t\"%s\"" v s))
+        (fun (s, v) ->
+          Meta (Printf.sprintf "%s:\t.string\t\"%s\"" (prefixed v) s))
         env#strings
     @ [
-        Meta "_init:\t.quad 0";
-        Meta "\t.section __DATA, custom_data, regular, no_dead_strip";
-        Meta (Printf.sprintf "filler:\t.fill\t%d, 8, 1" env#max_locals_size);
+        Meta (prefixed "init" ^ ":\t.quad 0");
+        (match os with
+        | Darwin ->
+            Meta "\t.section __DATA, custom_data, regular, no_dead_strip"
+        | Linux -> Meta "\t.section custom_data,\"aw\",@progbits");
+        Meta
+          (Printf.sprintf "%s:\t.fill\t%d, 8, 1" (prefixed "filler")
+             env#max_locals_size);
       ]
     @ List.concat
     @@ List.map
          (fun s ->
            [
              (* For mach-o STABS format is not supported: Meta
-               ( Printf.sprintf "\t.stabs \"%s:S1\",40,0,0,%s"
-                  (String.sub s (String.length "global_")
-                     (String.length s - String.length "global_"))
-                  s); *)
-             Meta (Printf.sprintf "%s:\t.quad\t1" s);
+                ( Printf.sprintf "\t.stabs \"%s:S1\",40,0,0,%s"
+                   (String.sub s (String.length "global_")
+                      (String.length s - String.length "global_"))
+                   s); *)
+             Meta (Printf.sprintf "%s:\t.quad\t1" (prefixed s));
            ])
          env#globals
   in
@@ -1263,8 +1290,8 @@ let genasm cmd prog =
     ([
        Meta (Printf.sprintf "\t.file \"%s\"" cmd#get_absolute_infile);
        (* For mach-o STABS format is not supported: Meta
-         ( Printf.sprintf "\t.stabs \"%s\",100,0,0,.Ltext"
-            cmd#get_absolute_infile); *)
+          ( Printf.sprintf "\t.stabs \"%s\",100,0,0,.Ltext"
+             cmd#get_absolute_infile); *)
      ]
     @ globals @ data
     @ [
@@ -1303,7 +1330,9 @@ let build cmd prog =
   cmd#dump_file "i" (Interface.gen prog);
   let inc = get_std_path () in
   let compiler = "clang" in
-  let flags = "-arch x86_64" in
+  let compiler_flags, linker_flags =
+    match os with Darwin -> ("-arch x86_64", "-ld_classic") | Linux -> ("", "")
+  in
   match cmd#get_mode with
   | `Default ->
       let objs = find_objects (fst @@ fst prog) cmd#get_include_paths in
@@ -1314,13 +1343,13 @@ let build cmd prog =
           Buffer.add_string buf " ")
         objs;
       let gcc_cmdline =
-        Printf.sprintf "%s -ld_classic %s %s %s %s.s %s %s/runtime.a" compiler flags
-          cmd#get_debug cmd#get_output_option cmd#basename (Buffer.contents buf)
-          inc
+        Printf.sprintf "%s %s %s %s %s %s.s %s %s/runtime.a" compiler
+          compiler_flags linker_flags cmd#get_debug cmd#get_output_option
+          cmd#basename (Buffer.contents buf) inc
       in
       Sys.command gcc_cmdline
   | `Compile ->
       Sys.command
-        (Printf.sprintf "%s %s %s -c -g %s.s" compiler flags cmd#get_debug
-           cmd#basename)
+        (Printf.sprintf "%s %s %s -c -g %s.s" compiler compiler_flags
+           cmd#get_debug cmd#basename)
   | _ -> invalid_arg "must not happen"
diff --git a/src/dune b/src/dune
index f99f6c3fb..3955618ef 100644
--- a/src/dune
+++ b/src/dune
@@ -46,7 +46,7 @@
 (library
  (name liba)
  (modules Language Pprinter stdpath version X86 SM)
- (libraries GT ostap)
+ (libraries GT ostap posix-uname)
  (flags
   (:standard
    -rectypes
diff --git a/stdlib/regression/Makefile b/stdlib/regression/Makefile
index b646a8d03..f8f4e24ab 100644
--- a/stdlib/regression/Makefile
+++ b/stdlib/regression/Makefile
@@ -2,13 +2,20 @@ TESTS=$(sort $(filter-out test02 test30, $(basename $(wildcard test*.lama))))
 
 LAMAC=../../src/lamac
 
+UNAME_S := $(shell uname -s)
+
+ifeq ($(UNAME_S),Linux)
+else ifeq ($(UNAME_S),Darwin)
+    ARCH = arch -x86_64
+endif
+
 .PHONY: check $(TESTS)
 
 check: $(TESTS)
 
 $(TESTS): %: %.lama
 	@echo "stdlib/regression/$@"
-	@LAMA=../../runtime $(LAMAC) -I .. -ds -dp $< && arch -X86_64 ./$@ > $@.log && diff $@.log orig/$@.log
+	@LAMA=../../runtime $(LAMAC) -I .. -ds -dp $< && $(ARCH) ./$@ > $@.log && diff $@.log orig/$@.log
 
 clean:
 	$(RM) test*.log *.s *~ $(TESTS) *.i