[Tutorial] SketchUp Ruby C Extension

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.

Dan Rathbun

@jim said:

I could not get MinGW working using Ruby 1.8.6.

Ruby v1.8.6-p287 was the last 'distro' to be compiled with MSVC. (.. which is likely why the GSUDT released SU8 with this patch level, even though their were newer v1.8.6 patch levels available.)

All patch levels above p287 were distro'd (via Windows One-Click Installer,) compiled with MinGW.

That is not to say, however that someone (including Google,) could build the newer patch levels with MSVC, or do a manual install by downloading precompiled binaries from:
ftp;//ftp.ruby-lang.org/pub/ruby/binaries/mswin32/
(.. However not all patch levels are available.)