Installing gosu on FreeBSD - ruby

Question

I'm trying to install this Ruby gem on FreeBSD, and it's failing with the following error:
# gem install gosu
Building native extensions. This could take a while...
ERROR: Error installing gosu:
ERROR: Failed to build gem native extension.
current directory: /usr/local/lib/ruby/gems/2.4/gems/gosu-0.14.5/ext/gosu
/usr/local/bin/ruby24 -I /usr/local/lib/ruby/site_ruby/2.4 -r ./siteconf20190322-6847-x8s25j.rb extconf.rb
The Gosu gem requires some libraries to be installed system-wide.
See the following site for a list:
https://github.com/gosu/gosu/wiki/Getting-Started-on-Linux
cat: /proc/cpuinfo: No such file or directory
checking for -lopenal... yes
checking for AL/al.h... yes
creating Makefile
current directory: /usr/local/lib/ruby/gems/2.4/gems/gosu-0.14.5/ext/gosu
make "DESTDIR=" clean
current directory: /usr/local/lib/ruby/gems/2.4/gems/gosu-0.14.5/ext/gosu
make "DESTDIR="
compiling ../../src/Audio.cpp
In file included from ../../src/Audio.cpp:17:
../../src/SndFile.hpp:111:33: warning: field 'buffer' is uninitialized when used here [-Wuninitialized]
: file(nullptr), reader(buffer.front_reader())
^
../../src/SndFile.hpp:123:33: warning: field 'buffer' is uninitialized when used here [-Wuninitialized]
: file(nullptr), reader(buffer.front_reader())
^
2 warnings generated.
compiling ../../src/AudioImpl.cpp
compiling ../../src/Bitmap.cpp
compiling ../../src/BitmapIO.cpp
compiling ../../src/BlockAllocator.cpp
compiling ../../src/Channel.cpp
compiling ../../src/Color.cpp
compiling ../../src/DirectoriesApple.cpp
compiling ../../src/DirectoriesUnix.cpp
compiling ../../src/DirectoriesWin.cpp
compiling ../../src/FileUnix.cpp
../../src/FileUnix.cpp:53:47: error: use of undeclared identifier 'S_IRUSR'
pimpl->fd = open(filename.c_str(), flags, S_IRUSR|S_IWUSR|S_IRGRP|S_IWGRP|S_IROTH|S_IWOTH);
^
../../src/FileUnix.cpp:53:55: error: use of undeclared identifier 'S_IWUSR'
pimpl->fd = open(filename.c_str(), flags, S_IRUSR|S_IWUSR|S_IRGRP|S_IWGRP|S_IROTH|S_IWOTH);
^
../../src/FileUnix.cpp:53:63: error: use of undeclared identifier 'S_IRGRP'
pimpl->fd = open(filename.c_str(), flags, S_IRUSR|S_IWUSR|S_IRGRP|S_IWGRP|S_IROTH|S_IWOTH);
^
../../src/FileUnix.cpp:53:71: error: use of undeclared identifier 'S_IWGRP'
pimpl->fd = open(filename.c_str(), flags, S_IRUSR|S_IWUSR|S_IRGRP|S_IWGRP|S_IROTH|S_IWOTH);
^
../../src/FileUnix.cpp:53:79: error: use of undeclared identifier 'S_IROTH'
pimpl->fd = open(filename.c_str(), flags, S_IRUSR|S_IWUSR|S_IRGRP|S_IWGRP|S_IROTH|S_IWOTH);
^
../../src/FileUnix.cpp:53:87: error: use of undeclared identifier 'S_IWOTH'
pimpl->fd = open(filename.c_str(), flags, S_IRUSR|S_IWUSR|S_IRGRP|S_IWGRP|S_IROTH|S_IWOTH);
^
6 errors generated.
*** Error code 1
Stop.
make: stopped in /usr/local/lib/ruby/gems/2.4/gems/gosu-0.14.5/ext/gosu
Other things I tried:
Switching compilers - from clang and c++ to g++ and gcc.
Cloning the repository and building "manually" - got the same errors.
Is it even possible to install it on FreeBSD? Searches didn't return anything useful.

Answer 1

On FreeBSD system headers are organized slightly differently than in Linux.
Quick man lookup reveals, that you need to
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
to make these definitions visible.