cgo and Python as a shared library

[Deiter]

macOS: 12.5.1

go: go1.19.3 darwin/amd64

I'm having trouble building a go module that uses Python as a shared library.

This code works:

...

package main

// #include <float.h>

import "C"

import "fmt"

func main() {

fmt.Println("Max float value of float is", C.FLT_MAX)

}

...

$ go run .

Max float value of float is 3.4028234663852886e+38

...

I run into problems when I try to include Python:
...

package main

/*

#cgo pkg-config: python3

#cgo LDFLAGS: -lpython3.8

*/

import "C"

import (

"fmt"

)

func main() {

C.Py_Initialize()

fmt.Println(C.GoString(C.Py_GetVersion()))

C.Py_Finalize()

}

...

$ go run .

# producer

./producer.go:16:2: could not determine kind of name for C.Py_Finalize
./producer.go:15:25: could not determine kind of name for C.Py_GetVersion
./producer.go:14:2: could not determine kind of name for C.Py_Initialize

...

Any suggestions? I'm guessing it has something to do w/ setting PKG_CONFIG_PATH and/or CGO_CFLAGS but I'm not certain...

[Deiter]

Doh! I forgot the include. I get a linker error now:

...

package main

/*

#cgo pkg-config: python3

#cgo LDFLAGS: -lpython3.8

#include <Python.h>

*/

import "C"

import (

"fmt"

)

func main() {

C.Py_Initialize()

fmt.Println(C.GoString(C.Py_GetVersion()))

C.Py_Finalize()

}

...

$ go run .

# producer
/usr/local/go/pkg/tool/darwin_amd64/link: running clang failed: exit status 1
ld: library not found for -lpython3.8
clang: error: linker command failed with exit code 1 (use -v to see invocation)

...

Clearly a library is missing but I'm not clear where to find it or how to inform the linker. Thanks.

[Howard Waterfall]

SOLVED!

It took a while to sort out the various locations.

Environment Variables:

....

export LIBRARY_PATH=/usr/local/Frameworks/Python.framework/Versions/3.9/lib
export PKG_CONFIG_PATH=/usr/local/Frameworks/Python.framework/Versions/3.9/lib/pkgconfig

....

Code:

...

package main

/*
#cgo pkg-config: python3

#cgo CFLAGS: -I/usr/local/Frameworks/Python.framework/Headers
#cgo LDFLAGS: -L/usr/local/Frameworks/Python.framework/Versions/3.9/lib -lpython3.9 -ldl -framework CoreFoundation

#include <Python.h>
*/
import "C"

import (
"fmt"
)

func main() {
C.Py_Initialize()
fmt.Println(C.GoString(C.Py_GetVersion()))
C.Py_Finalize()
}

...

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