From: Joshua Ballanco <jballanc@...>
Date: 2008-03-24T08:03:28+09:00
Subject: Re: extending ruby with C++

7stud -- wrote:

>> Where do those statements go?  Inside extconf.rb?
> 
> My current extconf.rb file:
> 
> require 'mkmf'
> 
> if (/mswin32/ =~ PLATFORM)
>     $CFLAGS+=" -GX "    # allow exceptions
> end
> 
> $LIBS << " -lstdc++ -lc"
> $CC =="g++"
> $CXX == $CC
> 
> create_makefile("Test")
> 
> The output:
> 
> $ ruby extconf.rb
> creating Makefile
> 
> $ make
> g++ -fno-common -g -Os -pipe -fno-common -pipe  -fno-common -pipe 
> -fno-common   -I. -I/usr/lib/ruby/1.8/universal-darwin8.0 
> -I/usr/lib/ruby/1.8/universal-darwin8.0 -I.   -c Test.cpp
> cc  -bundle  -L"/usr/lib" -o Test.bundle Test.o  -lruby  -lpthread -ldl 
> -lobjc   -lstdc++ -lc
> /usr/bin/ld: Undefined symbols:
> __Unwind_Resume
> collect2: ld returned 1 exit status
> make: *** [Test.bundle] Error 1
> 
> $ls
> Makefile        Test.cpp        Test.o          extconf.rb

I've run into this problem myself on OS X. For some reason, the mkmf 
library in Ruby 1.8 fails to properly realize that it should use g++ 
instead of gcc or cc for C++ files. (Luckily Ruby 1.9 doesn't have this 
problem ATM.) You need to explicitly tell mkmf to use g++ like so:

cpp_command('g++')

There's also the arch flags issue to worry about (Ruby, by default, 
tries to build universal, but many libraries build only one arch on OS 
X). I've com up with a fix for that as well. Including it you're 
extconf.rb should look like:

require 'mkmf'
require 'rbconfig'

if Config::CONFIG["arch"] =~ /universal-darwin/
  case `uname -smr`.chomp
    when "i386" : ENV['ARCHFLAGS'] = '-arch i386'
    when "ppc"  : ENV['ARCHFLAGS'] = '-arch ppc'
  end
  cpp_command('g++') if RUBY_VERSION < '1.9'
end

if (/mswin32/ =~ PLATFORM)
     $CFLAGS+=" -GX "    # allow exceptions
end


create_makefile("Test")
-- 
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