How to Integrate Go Functions into Existing C Projects: A Step-by-Step Guide with Solutions for Linking Errors?

How to Use Go in Existing C Projects

Integrating Go Functions into C Programs

Integrating Go functions into C programs involves building a Go file into an object file (.o) and incorporating it into the existing C project's archive (.a) file. This allows calling Go functions from within the C program.

Issues Encountered in Example Code

The example provided by the user showcases errors during the linking phase. These errors stem from a misunderstanding where GCCGO expects a main function in the Go file, unlike the C program.

Solution with Go 1.5 and Beyond

In Go 1.5 and later versions, this issue is addressed. It enables building C-compatible libraries using the Go tool. With this feature, the user can keep the C file (main.c) as given in the question, and update the Go file (main.go) as follows:

<code class="go">package main

import "C"
import "fmt"

//export PrintString
func PrintString(cs *C.char) {
    s := C.GoString(cs)
    fmt.Println(s)
}

func main() {}</code>

Building a Go Object File

To build the Go file into an object file, run the following command:

go build -buildmode c-archive -o mygopkg.a

Integrating into C Project

To link the Go object file with the C program (_main.c), use the following command to build the final binary:

gcc -o main _main.c mygopkg.a -lpthread

Alternative Approach for Shared Libraries

If you prefer to build a shared library with Go, the following command will create mygopkg.so:

go build -buildmode c-shared -o mygopkg.so

To link the shared library with _main.c, run this command:

LD_RUN_PATH=$(pwd) gcc -o main _main.c mygopkg.so -lpthread

Note: Set LD_RUN_PATH to ensure the linker locates the shared library in the current directory during runtime.

For further details and insights, refer to the Go execution modes design document.

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