draffensperger/go-interlang

Examples of calls between Go and C/C++ (and how to call a Go shared object from Node/Ruby/Python/Java)

Go interlanguage call examples

Examples of calls between Go and C/C++ and calling Go from dynamic languages.

The examples are designed to work on Mac and Linux. If you're using Windows, feel free to reach out to me to request updates for examples that don't work correctly.

Calls from Go to C (go_to_c folder)

These examples use cgo to enable calls to C.

• Calling a C snippet in the cgo comment: c_in_comment
• Calling a C statically-linked library (.a file): static_c_lib
• Calling a C dynamically-linked library (.so or .dylib): dynamic_c_lib

Calls from Go to C++ (go_to_cxx folder)

C++ has more complex calling conventions (e.g. function overloading, inheritance, templates) and so it uses name mangling which adds a step when calling it from Go. Below are ways to do it.

• Calling C++ via a C wrapper function: c_wrapper
• Calling C++ via an auto-generated SWIG wrapper: swig

Calls from C/C++ to Go (c_to_go folder)

• Calling from Go to C and back again: to_c_and_back
• Passing a Go func as function pointer callback to C: callbacks
• Calling a Go static library with buildmode=c-archive from C: static_go_lib
• Calling a Go dynamic lib from C++ cxx_to_go_dyn_lib
• Calling Go from C using gccgo

Calls from Python/Node.js/Ruby/Java to Go (dyn_langs_to_go folder)

Go now allows building a C-compatible dynamically-linked library with buildmode=c-shared. That allows any language that can call C dynamic libraries to call Go.

• Call from Python via ctypes: python_to_go.py
• Call from Node.js via ffi npm module: nodejs_to_go.js
• Call from Ruby via ffi gem: ruby_to_go.rb
• Call from Java via JNA: JavaToGo.java

Cross-language call benchmarks

There is a cost to calling between languages a Go to C call is about 50x slower than a pure Go call and a Ruby FFI call is about 30x slower than a pure Ruby call. For more details, see the benchmarks section.

Helpful Links

Cgo documentation: golang.og/cmd/cgo/

Documentation for go command (see especially go build section and "Calling between Go and C"): golang.org/cmd/go/

SWIG Documentation: swig.org

SWIG Go examples: github.com/swig/swig/tree/master/Examples/go

Gccgo documentation: golang.org/doc/install/gccgo

License

The code in this repo is MIT Licensed.

go-interlang's Issues

Compile error: I can't call exported go function in C++

I followed your example in cxx_to_go_dyn_lib. I want to export go functions in infiniband go module so that they are callable from C++. I manage to generate the .h header files but when I compile my C++ code it bumps out with the following error:

./src/github.com/jsgilmore/ib/libadder.so(_all.o): In function Initialize': /tmp/go-build/github.com/jsgilmore/ib/_obj/_cgo_export.c:33: undefined reference to _cgo_wait_runtime_init_done'
/tmp/go-build/github.com/jsgilmore/ib/_obj/_cgo_export.c:38: undefined reference to `_cgoexp_1f5f6ba4e969_Initialize'

Didn't get much help from the internet on this error. I will appreciate your input.
P.S. The file that contains the the exported go functions has an "import C" declaration with commented includes. Could this be an issue?

external c library

Hi,
do you know how I can call and link an external c/c++ library in callback or adder?
I can call from the main, but not in the .c/.h files of the callback project.
Thanks a lot
Angelo

easier to wrap c or c++?

I am trying to write a wrapper for this:
https://github.com/TommyKaneko/Sketchup-API-C-Wrapper

They have a c and cpp wrapper over the c.
SO which is easier from a golang perspective ?
Would really appreciate your advice as I have never really done much of this golang to c work before.

CGO's generated code does not have meaningful parameter and returned variable names

Is there a way to ensure that the generated header files (.h files) have function parameters and structs with meaningful variable names? What I notice is that cgo just follows some pattern e.g., r0, r1... or p0, p1...

Can we call Go From C++ using SWIG

I know we can call C++ from Go using SWIG.
But can we call Go From C++ using SWIG?

GO binding struct for a self referencing struct

Hi,

Any ideas on how to write a golang equivalent struct for self referencing struct something like this -

typedef struct WRITER {
int version;
int (WriteBlock)(struct WRITER thisPtr,
const void* dataBufferPtr,
unsigned long bufferSize);
} WRITER;

Thanks.