From: Eric Hodel <drbrain@...7.net>
Date: 2012-06-01T03:04:10+09:00
Subject: Re: [C exten] extconf.rg and #ifdef

On May 28, 2012, at 03:57, Iņaki Baz Castillo wrote:

> Hi, depending whether my Ruby C extension is being compiled on *nix or
> Windows, I need some #defines (i.e: OS_UNIX or OS_WIN).
> 
> I see no way in MKMF documentation to generate a #define (based on
> RbConfig["host_os"] for example).

Do not use host_* values from rbconfig.rb.

Use target_* values from rbconfig.rb.

Using host_* is wrong.

The host_* values come from host that compiled ruby.  When ruby is cross-compiled these values won't match the target and your gem will fail to compile.

You should use target_* values as these values match the target ruby was compiled for.

See: http://sources.redhat.com/autobook/autobook/autobook_261.html