Why do erlang builds include .c and .erl source?

0
votes

I am not even a newbie to erlang yet, I am just using RabbitMQ, which is written in Erlang. After I run configure/make/make install, the build output directories have plenty of .c and .erl files. Is this necessary? What's the reasoning behind it? some examples:

  • ./lib/erlang/lib/erl_interface-3.7.6/src/misc/show_msg.c
  • ./lib/erlang/lib/cosNotification-1.1.18/src/oe_CosNotification.erl
1
erlang

1 Answers

2
votes

Yes, it's necessary. The runtime system of Erlang is written in C, and most of the standard library is written in Erlang.

What's the reasoning behind it?

What would be the alternative? In order to execute any Erlang code, you need to have the runtime system already started, and so it can't be written in Erlang. It could be written in:

  1. Assembly

  2. C

  3. C++ or some other language

  4. Erlang could be executed without a runtime

Assembly is obviously a bad choice: you'd have to rewrite it nearly completely for any new CPU target and it would be much harder to maintain.

C provides excellent performance and portability, and ability to call C code from Erlang would at any rate be required. This is the choice made not only by Erlang, but by Python, Ruby, Perl, etc. as well.

C++ complicates portability (some OSes have C compilers available, but not C++ compilers; quality of C++ compilers varies more); other languages even more so (along with performance, possibly requiring their own runtime, etc.).

The final option would make Erlang a completely different language.