How to Call C++ from Go

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└── src
    └── cgotest
        ├── hello
        │   ├── cpp
        │   │   └── hellocpp.cpp
        │   ├── hello.go
        │   ├── include
        │   │   └── hellocpp.h
        │   └── lib
        │       └── libhellocpp.so
        └── main.go

hellocpp.h

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#ifndef _HELLOCPP_H_ #define _HELLOCPP_H_   #ifdef __cplusplus extern "C" { #endif     void SayHello(); #ifdef __cplusplus } #endif   #endif

hellocpp.cpp

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#include <iostream> #include "hellocpp.h" using namespace std;   void SayHello() {     cout << "Hello from C++" << endl; }

Let's now create a C++ shared library.

cd $GOPATH/src/cgotest/hello
mkdir lib
g++ -Wall -shared -fpic cpp/hellocpp.cpp -Iinclude -o lib/hellocpp.so

hello.go

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package hello   // #cgo CFLAGS: -Iinclude // #cgo LDFLAGS: -Llib -lhellocpp // #include "hellocpp.h" import "C"   func HelloFromCpp() {     C.SayHello() }

main.go

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package main   import "cgotest/hello"   func main() {     hello.HelloFromCpp() }

There seems to be a bug that makes setting relative paths in LDFLAGS not to work. The workaround is to set LIBRARY_PATH env variable using absolute path.

cd $GOPATH
export LIBRARY_PATH=$GOPATH/src/cgotest/hello/lib
export LD_LIBRARY_PATH=$LIBRARY_PATH
go build cgotest
./cgotest

Output:

Hello from C++