skeleton nif that runs

Makefile

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+OTPROOT=/Users/schacon/otp_src_R13B03
+INCLUDES = -I$(OTPROOT)/erts/emulator/beam/
+
+# OS X flags.
+GCCFLAGS = -O3 -fPIC -bundle -flat_namespace -undefined suppress -fno-common -Wall -m32
+
+# Linux Flags
+#GCCFLAGS = -O3 -fPIC -shared -fno-common -Wall
+
+CFLAGS = $(GCCFLAGS) $(INCLUDES)
+LDFLAGS = $(GCCFLAGS) $(LIBS)
+
+OBJECTS = geef.o
+
+DRIVER = geef.so
+BEAM = geef.beam
+
+all: $(DRIVER) $(BEAM)
+
+clean: 
+	rm -f *.o *.beam $(DRIVER)
+	
+$(DRIVER): $(OBJECTS)
+	gcc -o $@ $^ $(LDFLAGS)
+	
+$(BEAM): geef.erl
+	erlc $^
+

geef.c

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+#include "erl_nif.h"
+
+static int
+load(ErlNifEnv* env, void** priv, ERL_NIF_TERM load_info)
+{
+    return 0;
+}
+
+static int
+reload(ErlNifEnv* env, void** priv, ERL_NIF_TERM load_info)
+{
+    return 0;
+}
+
+static int
+upgrade(ErlNifEnv* env, void** priv, void** old_priv,
+          ERL_NIF_TERM load_info)
+{
+    return 0;
+}
+
+static void
+unload(ErlNifEnv* env, void* priv)
+{
+    return;
+}
+
+static ERL_NIF_TERM
+object_exists(ErlNifEnv* env, ERL_NIF_TERM a1)
+{
+    unsigned long val;
+    if(!enif_get_ulong(env, a1, &val)) {
+        return enif_make_badarg(env);
+    } else {
+        return enif_make_ulong(env, val*2);
+    }
+}
+
+static ErlNifFunc geef_funcs[] =
+{
+    {"object_exists", 1, object_exists}
+};
+
+ERL_NIF_INIT(geef, geef_funcs, load, reload, upgrade, unload)

geef.erl

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+-module(geef).
+-export([start/0, object_exists/1]).
+
+start() ->
+    erlang:load_nif("geef", 0).
+
+object_exists(_Val) ->
+    nif_error(?LINE).    
+
+nif_error(Line) ->
+    exit({nif_not_loaded,module,?MODULE,line,Line}).

test

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+#!/Users/schacon/otp_src_R13B03/bin/escript
+%% -*- erlang -*-
+%%! debug verbose -noshell
+
+main([Object]) ->
+    try
+        geef:start(),
+        Test = geef:object_exists(4),
+        io:format("factorial ~s:~w~n", [Object, Test])
+    catch
+        _:_ ->
+            usage()
+    end;
+main(_) ->
+    usage().
+        
+usage() ->
+    io:format("usage: factorial integer\n"),
+    halt(1).
+