From: Daniel Berger <Daniel.Berger@...>
Date: 2005-12-06T04:21:37+09:00
Subject: Re: Determining endianness in extconf.rb

Aaron Patterson wrote:
> Hi.  Hopefully this is the right list for this question!
> 
> I am writing an extension for Ruby in C, and I need to determine
> the endianness of the machine and set a flag when I compile.  What is
> the best way to go about this?  I've seen examples of determining
> endianness but I don't know how to set the flag in extconf.rb
> 
> Any help would be greatly appreciated.  Thank you!
> 
> --Aaron
> 
> 

Modify $CFLAGS or $CPPFLAGS directly:

# extconf.rb
if [1].pack("I") == [1].pack("N")
    $CFLAGS += " -DBIG_ENDIAN" # note the leading space
end

/* In your C code somewhere */
#ifdef BIG_ENDIAN
    /* Do something */
#endif

Regards,

Dan