blog.kempkens.io/_posts/2014-12-24-supporting-deprecated-types-with-erlang-mk.md

layout	title	description	date	category	tags	comments
post	Supporting Deprecated Types with erlang.mk	Simple workaround for supporting deprecated types and warnings_as_errors with erlang.mk.	2014-12-24 13:25:00 CET	posts	erlang programming english	true

In April I wrote about how I use the platform_define feature of rebar to make deprecated types work without removing warnings_as_errors. I have switched to erlang.mk since then, but needed a similar feature for one of my libraries.

Since erlang.mk only uses make, adding support for a platform_define-like feature is very straightforward.

{% highlight makefile %} otp_release = $(shell erl -noshell -eval 'io:format("~s", [erlang:system_info(otp_release)]), init:stop()') otp_17plus = $(shell echo $(otp_release) | grep -q -E "^:digit:+$$" ; echo ?) {% endhighlight %}

The first variable (otp_release) will contain the OTP version (e.g. 17). The second variable (otp_17plus) will be either 0 or 1, depending on wether or not otp_release matches a regular expression. The regular expression checks if otp_release is just a number (e.g. 17) or not (e.g. R16B03-1).

That's enough to conditionally add options to erlc.

{% highlight makefile %} ifeq ($(otp_17plus),0) ERLC_OPTS += -Dnamespaced_types=1 TEST_ERLC_OPTS += -Dnamespaced_types=1 endif {% endhighlight %}

This will define namespaced_types only on Erlang 17+, allowing us to use the same ifdef-switch from April.

{% highlight erlang linenos %} -ifdef(namespaced_types). -type xxx_dict() :: dict:dict(). -else. -type xxx_dict() :: dict(). -endif. {% endhighlight %}