From: Ryan Davis <ryand-ruby@...>
Date: 2011-06-25T05:22:12+09:00
Subject: Re: Explicitly setting compiler to C++ in extconf.rb...


On Jun 24, 2011, at 11:50 , Antonio Terceiro wrote:

> Michael Edgar escreveu isso aí:
>> On Jun 23, 2011, at 7:30 PM, Antonio Terceiro wrote:
>> 
>>> require 'rbconfig'
>>> RbConfig::CONFIG['CPP'] = RbConfig::CONFIG['CPP'].gsub('gcc', 'g++')
>>> require 'mkmf'
>>> have_header('string') or raise('You need <string>')
>>> create_makefile('test')
>> 
>> Don't do this. The following is sufficient:
>> 
>> require 'mkmf'
>> have_library('stdc++')
>> create_makefile('laser/BasicBlock')
>> 
>> That's a working extconf.rb for a gem I'm actively working on. Adding stdc++
>> makes mkmf use g++ on my system.
> 
> Actualy mkmf uses g++ for C++ code (.cc,.cpp), and not because you
> checked for 'stdc++'
> 
> The original problem is not checking for a C++ standard header, is
> checking for a header that is actually a C++ header that happens to
> #include a C++ standard header. Doing that with `gcc -E` instead of `g++
> -E` will just not work.
> 
> Of course, mkmf could provide a way to say "please check for everything
> using C++ instead of C".

mkmf provides:

with_cflags(flags) # :yields:

so you should be able to do something like

with_cflags("-x c++") do
  # ...
end