[opensuse-ruby] FFI library for ruby C/C++ extensions
Hi, I would like to point to interesting library for C extension to ruby. short: just look at https://github.com/ffi/ffi how you can do quick and easy C bindings from ruby code ( so no C code needed ). For C++ you should look at https://github.com/jasonroelofs/rbplusplus long story: We discussing on lunch about various quality of C bindings ( hating perl C bindings :) ) and we remembered that duncan do something with it, but I cannot remember more details. Martin think that FFI is about making C api better but need to write in C. So I look into it how it works and are quite surprised that 1) you write it in ruby 2) is really straight forward 3) doesn't work well C++ ( let me fix it if I understand it wrong ). But I found that exists also library for it rb++ https://github.com/jasonroelofs/rbplusplus I think it is much better option then generating interface with Swig which is quite buggy and limited, especially for complex C++ and resul is not nice ( often object hierarchy is broken ). Josef -- To unsubscribe, e-mail: opensuse-ruby+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse-ruby+owner@opensuse.org
On 08/01/14 17:15, Josef Reidinger wrote:
We discussing on lunch about various quality of C bindings ( hating perl C bindings :) ) and we remembered that duncan do something with it, but I cannot remember more details. Martin think that FFI is about making C api better but need to write in C. So I look into it how it works and are quite surprised that
I was maintaining some rpm bindings that were dated from ruby 1.6 times. The C code was painful to work with, so I rewrote the whole thing in pure ruby using ffi. https://github.com/dmacvicar/ruby-rpm-ffi The API is mostly compatible, but it does not support install operations yet, and it targets rpm 4.9 only.
1) you write it in ruby
Yes.
2) is really straight forward
Yes. But you have to be careful, there are some tradeoffs * if the library API changes your extension will not stop compiling. You have to have good testcases. * Some libs are annoying when they use macros in headers, and you can't access those. * You have to be more careful if you want to support multiple target libraries. In a C extension it is more straightforward with #ifdef and version macros/defines. In ruby is the same but you have less information at your disposal. * I am not sure if ffi is supported on all architectures. Check for s390x and others.
3) doesn't work well C++ ( let me fix it if I understand it wrong ).
The problem is the ABI and name mangling. Even if it worked, you would be able to call functions, so it would not be an automatic mapping to the classes. rbplusplus is a different approach. They use gcc xml output to have the class metadata, and then convert that to C++ code, using a library call rice that wraps the MRI C API in C++. You still need to generate C++ in order to call C++ code or create a small C library that exposes a plain C api for the C++ API and then call that from FFI. Or you can implement the mangling for gcc4 and call C++ directly... -- Duncan Mac-Vicar P. - http://www.suse.com/ SUSE LINUX Products GmbH, GF: Jeff Hawn, Jennifer Guild, Felix Imendörffer, HRB 16746 (AG Nürnberg) Maxfeldstraße 5, 90409 Nürnberg, Germany -- To unsubscribe, e-mail: opensuse-ruby+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse-ruby+owner@opensuse.org
On 10/01/14 10:17, Duncan Mac-Vicar P. wrote:
On 08/01/14 17:15, Josef Reidinger wrote: Or you can implement the mangling for gcc4 and call C++ directly...
BTW, this guy already did a bit of it: http://rubydoc.info/github/nasser/zajal/FFI/Cpp
participants (2)
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Duncan Mac-Vicar P. -
Josef Reidinger