Add handling of erlang version based compiler macros

The mechanism has been copied from LFE and is more general than
necessary here but this makes it easier to maintain. We are even
future rebar compliant.

Makefile

@@ -1,4 +1,4 @@
-# Copyright (c) 2014 Robert Virding
+# Copyright (c) 2016 Robert Virding
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
@@ -12,41 +12,47 @@
 # See the License for the specific language governing permissions and
 #  limitations under the License.
 
-# Luerl Makefile
+# Makefile for Luerl
 # Building from .xrl, .yrl and .erl
 # Intermediaries from leex and yecc stay in ./src
 
 SRCDIR        =./src
-BEAMDIR       =./ebin
-ERL_SOURCES  := $(wildcard $(SRCDIR)/*.erl)
-XRL_SOURCES  := $(wildcard $(SRCDIR)/*.xrl)
-YRL_SOURCES  := $(wildcard $(SRCDIR)/*.yrl)
-ERL_MODULES  := $(ERL_SOURCES:$(SRCDIR)/%.erl=%)
-XRL_MODULES  := $(XRL_SOURCES:$(SRCDIR)/%.xrl=%)
-YRL_MODULES  := $(YRL_SOURCES:$(SRCDIR)/%.yrl=%)
-XRL_INTERM   := $(XRL_MODULES:%=$(SRCDIR)/%.erl)
-YRL_INTERM   := $(YRL_MODULES:%=$(SRCDIR)/%.erl)
-MODULES      := $(XRL_MODULES) $(YRL_MODULES) $(ERL_MODULES)
-OBJECTS      := $(MODULES:%=$(BEAMDIR)/%.beam)
-
-all: $(OBJECTS)
-
-$(BEAMDIR)/%.beam: $(SRCDIR)/%.erl $(SRCDIR)/luerl.hrl
-	@ mkdir -p $(BEAMDIR) 
-	erlc $(ERLCFLAGS) -o $(BEAMDIR) $<
+EBINDIR       =./ebin
+
+ESRCS  := $(notdir $(wildcard $(SRCDIR)/*.erl))
+XSRCS  := $(notdir $(wildcard $(SRCDIR)/*.xrl))
+YSRCS  := $(notdir $(wildcard $(SRCDIR)/*.yrl))
+EBINS = $(ESRCS:.erl=.beam) $(XSRCS:.xrl=.beam) $(YSRCS:.yrl=.beam)
+
+ERLCFLAGS = -W1
+ERLC = erlc
+
+all: compile
+
+.PHONY: compile clean echo examples
+
+compile: comp_opts.mk $(addprefix $(EBINDIR)/, $(EBINS))
+
+$(EBINDIR)/%.beam: $(SRCDIR)/%.erl $(SRCDIR)/luerl.hrl comp_opts.mk
+	@ mkdir -p $(EBINDIR)
+	$(ERLC) $(ERLCFLAGS) -o $(EBINDIR) $(COMP_OPTS) $(ERLCFLAGS) $<
 
 %.erl: %.xrl
-	erlc -o $(SRCDIR) $<
+	$(ERLC) -o $(SRCDIR) $<
 
 %.erl: %.yrl
-	erlc -o $(SRCDIR) $<
+	$(ERLC) -o $(SRCDIR) $<
+
+comp_opts.mk:
+	escript get_comp_opts.escript
+
+-include comp_opts.mk
 
 clean:
-	@ rm -f $(BEAMDIR)/*.beam
+	@ rm -f $(EBINDIR)/*.beam
 	@ rm -f *.beam
 	@ rm -f erl_crash.dump
-	@ rm -f $(XRL_INTERM)
-	@ rm -f $(YRL_INTERM)
+	@ rm comp_opts.mk
 	$(MAKE) -C examples clean
 
 echo: 

get_comp_opts.escript

@@ -0,0 +1,48 @@
+#! /usr/bin/env escript
+%% -*- mode: erlang; indent-tabs-mode: nil -*-
+%% Define a number of compiler options. We first work out the current
+%% Erlang version and from the we can define the various options.
+
+%% Bloody useful.
+-define(IF(Test,True,False), case Test of true -> True; false -> False end).
+
+%% Define the makefile variables HAS_MAPS and HAS_FULL_KEYS depending
+%% on whether this version of erlang has maps (17) and general map
+%% keys (18), or NEW_CORE_REC for new core definition of records (19).
+
+-define(HAS_MAPS_OPT, "-DHAS_MAPS=true").
+-define(FULL_KEYS_OPT, "-DHAS_FULL_KEYS=true").
+-define(NEW_REC_OPT, "-DNEW_REC_CORE=true").
+-define(NEW_RAND_OPT, "-DNEW_RAND=true").
+
+main(_) ->
+    Version = otp_release(),
+    CompOpts = comp_opts(Version),
+    file:write_file("comp_opts.mk", "COMP_OPTS = " ++ CompOpts ++ "\n").
+
+comp_opts(Version) ->
+    Copts0 = "-DERLANG_VERSION=" ++ Version,
+    Copts1 = ?IF(Version >= "17", Copts0 ++ " " ++ ?HAS_MAPS_OPT, Copts0),
+    Copts2 = ?IF(Version >= "18", Copts1 ++ " " ++ ?FULL_KEYS_OPT, Copts1),
+    Copts3 = ?IF(Version >= "19",
+                 Copts2 ++ append_copts([?NEW_REC_OPT,?NEW_RAND_OPT]),
+                 Copts2),
+    Copts3.
+
+append_copts([Copt|Copts]) ->
+    " " ++ Copt ++ append_copts(Copts);
+append_copts([]) -> [].
+
+%% Get the major release number.
+%% We have stolen the idea for this code from rebar3.
+
+otp_release() ->
+    case erlang:system_info(otp_release) of
+        [$R,N1,N2|_] when is_integer(N1), is_integer(N2) ->
+            %% If OTP <= R16, take the digits.
+            [N1,N2];
+        Rel ->
+            %% If OTP >= 17.x, erlang:system_info(otp_release) returns just
+            %% the major version number.
+            Rel
+    end.

rebar.config.script

@@ -0,0 +1,33 @@
+%% -*- mode: erlang; indent-tabs-mode: nil -*-
+
+Conf0 = CONFIG,
+HasOpt = {d,'HAS_MAPS',true},
+FullOpt = {d,'HAS_FULL_KEYS',true},
+RecOpt = {d,'NEW_REC_CORE',true},
+RandOpt = {d,'NEW_RAND',true},
+
+Version = case erlang:system_info(otp_release) of
+              [$R,N1,N2|_] when is_integer(N1), is_integer(N2) ->
+                  [N1,N2];
+              Rel -> Rel
+          end,
+
+Copts0 = [{d,'ERLANG_VERSION',Version}],
+Copts1 = if Version >= "17" -> Copts0 ++ [HasOpt];
+            true -> Copts0
+         end,
+Copts2 = if Version >= "18" -> Copts1 ++ [FullOpt];
+            true -> Copts1
+         end,
+Copts3 = if Version >= "19" -> Copts2 ++ [RecOpt,RandOpt];
+            true -> Copts2
+         end,
+Copts = Copts3,                                 %This is it
+
+case lists:keyfind(erl_opts, 1, Conf0) of
+    {erl_opts,Opts} ->                          %Existing erl_opts
+        NewOpts = {erl_opts,Opts ++ Copts},
+        lists:keyreplace(erl_opts, 1, Conf0, NewOpts);
+    false ->                                    %No erl_opts
+        Conf0 ++ [{erl_opts,Copts}]
+end.