TMPDIR = os:getenv("TMPDIR", "/tmp"),

Compile = fun(Name0, Prog) ->
    Name = filename:join(TMPDIR, Name0),
    ok = file:write_file(Name, Prog, [write, exclusive]),
    Cmd = erlang:open_port({spawn, ["${CC-cc} -o /dev/null ", Name]},
            [stream, exit_status]),
    Status = receive
        {Cmd, {exit_status, 0}} ->
            true;
        {Cmd, {exit_status, _}} ->
            false
    end,
    ok = file:delete(Name),
    Status
end,

Test = fun(Name, Prog, Supported, Unsupported) ->
    case Compile(Name, Prog) of
        true ->
            Supported;
        false ->
            Unsupported
    end
end,

Only = fun(OS, Name, Prog, Supported, Unsupported) ->
    case os:type() of
        OS ->
            Test(Name, Prog, Supported, Unsupported);
        _ ->
            Unsupported
    end
end,

Linux = fun(Name, Prog, Supported, Unsupported) ->
    Only({unix,linux}, Name, Prog, Supported, Unsupported)
end,

Append = fun(Str, Flag) ->
    string:join(sets:to_list(sets:add_element(Flag,
                    sets:from_list(string:tokens(Str, " ")))), " ")
end,

Setenv = fun(_Key, "") ->
                true;
            (Key, Val) ->
                Cur = os:getenv(Key, ""),
                os:putenv(Key, Append(Cur, Val))
end,

%%
%% Tests
%%

% Linux: support for setns(2)
Setns = fun(Config) ->
    Prog = "
#define _GNU_SOURCE
#include <sched.h>
int main(int argc, char *argv[]) {
    (void)setns(0,0);
    return 0;
}",
    case os:getenv("CROSSCOMPILE") of
        false ->
            Flag = Linux("test_setns.c", Prog, "-DHAVE_SETNS", ""),
            true = Setenv("PROCKET_DEFINE", Flag);
        _ ->
            true
    end,
    Config
end,

lists:foldl(fun(Fun, Cfg) ->
        Fun(Cfg)
    end,
    CONFIG,
    [Setns]
).