[Tutorial] SketchUp Ruby C Extension

Dan Rathbun

Don't forget the "help" topic here:
[Info] C/C++ Ruby extensions & SketchUp plugins
.. and read Adan Nelson's posts (links on the above list.)

Dan Rathbun

from the info file "win32.readme" in the Ruby C source:
@unknownuser said:

You can NOT use a path name [that] contains any white space characters as
the ruby source directory, this restriction comes from the behavior of include directives of NMAKE.
(- you may call it a bug. -)

tbd

Thom: #pragma comment(lib, "*.lib") adds the libraries to the link phase (that hold imports and functions code)

it was a way to make sure that it will compile even if you create a new project and don't use in mine in PellesC.

thomthom

Right'o! Gotcha. Been reading more up on C and GCC.

tomasz

Thanks Thomas for the example.

I do not understand what is 'extconf.rb' for. I have compiled my extension under VC++ 2008 without running the file and without using any makefile... Is it bad ?

tbd

extconf.rb - external configuration, it generates the makefile to create the extension. using makefile you can automate builds and tests.

thomthom

extconf.rb generates a make file you can use with make under OSX and nmake under Windows.
http://ruby-doc.org/docs/ProgrammingRuby/html/ext_ruby.html#UG

thomthom

@unknownuser said:

I have compiled my extension under VC++ 2008

How big difference is making a Ruby Extension in C++ as oppose to C? ...seeing how Ruby is built in C...

tomasz

@unknownuser said:

extconf.rb - external configuration, it generates the makefile to create the extension. using makefile you can automate builds and tests.

Got it! In VC++ I have to configure it on my own.

@thomthom said:

How big difference is making a Ruby Extension in C++ as oppose to C? ...seeing how Ruby is built in C...

You certainly would need to enclose declaration of the extension initialization with extern "C":

extern "C" {
void Init_SX_HelloWorld(); 
}

I am not really an expert, but I guess all the rest would stay same.

thomthom

Added a new example with basic functions. Will start on the tutorial text and images next.

Btw, does anyone know how one can make extconf.rb and make/nmake output their files to a given folder? I'd like to make it so that each platform outputs its generated files to separate directories.

Chris Fullmer

What C++ compiler or development environment are you going to write this for so I can go download it and start poking around in it?

thomthom

I am writing the extensions in C. But under windows I installed Visual C++ Express 2010 because it has the required Windows headers and nmake to compile it. I have some crude notes in the README.txt in the repo. Under OSX you need X Tools from the OSX DVD.

thomthom

Note that I never use the Visual C++ IDE editor.

Jim

Just wondering if there's any reason that MinGW instead of MSVC++ could not be used to compile c extensions. I assume the c extension is a libaray and doesn't require any Windows-specific GUI stuff - it's just a library of functions, right?

Dan Rathbun

@thomthom said:

Btw, does anyone know how one can make extconf.rb and make/nmake output their files to a given folder? I'd like to make it so that each platform outputs its generated files to separate directories.

Did you check the methods defined in "mkmf.rb" ?
(You can also see "Appendix C. Functions Available in extconf.rb" in the "README.EXT" file.)

.. also check our the "extmk.rb" file in the ext dir.

thomthom

@jim said:

Just wondering if there's any reason that MinGW instead of MSVC++ could not be used to compile c extensions. I assume the c extension is a libaray and doesn't require any Windows-specific GUI stuff - it's just a library of functions, right?

Dunno. I'd think it'd be possible. But I really have no clue when it comes to compiling. It'd be nice to have tutorials for different compilers. So please feel free to jump on the bandwagon )

thomthom

@dan rathbun said:

Did you check the methods defined in "mkmf.rb" ?
(You can also see "Appendix C. Functions Available in extconf.rb" in the "README.EXT" file.)

.. also check our the "extmk.rb" file in the ext dir.

Yea, got a wee bit lost...

Dan Rathbun

@thomthom said:

Yea, got a wee bit lost...

I know (insert head-spinning emoticon here).

Lets try these:
A Simple Makefile Tutorial

Makefile Tutorial

I think the constant you want is DESTDIR or $(DESTDIR)

thomthom

Will have a look. Currently when I use nmake I get some warning about some of the compiler flags. Maybe I can eliminate them. I'd prefer that so there's less noise coming from the compiler. Easier to spot other warnings.

( That first link is sightly messed up though, as they didn't escape angle brackets inside the code examples: #include <hellomake.h> eaten by the browser - at least under Firefox.

I've come across a partial documentation of mkmf: http://www.ensta-paristech.fr/~diam/ruby/online/ruby-doc-stdlib/libdoc/mkmf/rdoc/index.html

Jim

@thomthom said:

Dunno. I'd think it'd be possible. But I really have no clue when it comes to compiling. It'd be nice to have tutorials for different compilers. So please feel free to jump on the bandwagon )

I could not get MinGW working using Ruby 1.8.6. I could get the examples to compile using Ruby 1.9.3, but they just crashed SketchUp.

But both example seem to compile and work just fine in SketchUp using VC++ Express and Ruby 1.8.6 per your instructions in the Readme file.