Question

我尝试使用Go构建示例共享对象库。代码编译（使用命令go build -o libsample.so -buildmode=c-shared .），成功构建了一个共享对象库 - 但是当通过JNA（来自Java）或ctypes（来自python）访问导出的方法时，我感到恐慌。我在Go中写的代码是：

// package name: libsample.so
package main

import "C"
import "fmt"

//export Hello
func Hello(s string) {
    fmt.Println("Hello " + s + "!")
}

func main() {
}

从Java访问此方法Hello：

import com.sun.jna.*;

public class sample {

    public interface GoSO extends Library {
        GoSO INSTANCE = (GoSO) Native.loadLibrary("sample" ,GoSO.class);
        void Hello(String s);
    }
    public static void main(String[] args) {
        GoSO.INSTANCE.Hello("World");
    }
}

或来自Python：

#!/usr/bin/python
import ctypes
lib = ctypes.CDLL("./libsample.so")
lib.Hello("World")

我收到以下错误：

runtime: out of memory: cannot allocate 140042998120448-byte block (1048576 in use)
fatal error: out of memory

runtime stack:
runtime.throw(0x7f5e434bfe50, 0xd)
    /usr/local/go/src/runtime/panic.go:530 +0x92
runtime.largeAlloc(0x7f5e4d27dc8d, 0xc800000003, 0xc82003cf08)
    /usr/local/go/src/runtime/malloc.go:768 +0xdf
runtime.mallocgc.func3()
    /usr/local/go/src/runtime/malloc.go:664 +0x35
runtime.systemstack(0x7f5e4e4d3ab8)
    /usr/local/go/src/runtime/asm_amd64.s:291 +0x72
runtime.mstart()
    /usr/local/go/src/runtime/proc.go:1048

goroutine 17 [running, locked to thread]:
runtime.systemstack_switch()
    /usr/local/go/src/runtime/asm_amd64.s:245 fp=0xc82003cb50 sp=0xc82003cb48
runtime.mallocgc(0x7f5e4d27dc8d, 0x0, 0x3, 0x0)
    /usr/local/go/src/runtime/malloc.go:665 +0x9fe fp=0xc82003cc28 sp=0xc82003cb50
runtime.rawstring(0x7f5e4d27dc8d, 0x0, 0x0, 0x0, 0x0, 0x0)
    /usr/local/go/src/runtime/string.go:284 +0x72 fp=0xc82003cc70 sp=0xc82003cc28
runtime.rawstringtmp(0x0, 0x7f5e4d27dc8d, 0x0, 0x0, 0x0, 0x0, 0x0)
    /usr/local/go/src/runtime/string.go:111 +0xb9 fp=0xc82003cca8 sp=0xc82003cc70
runtime.concatstrings(0x0, 0xc82003ce38, 0x3, 0x3, 0x0, 0x0)
    /usr/local/go/src/runtime/string.go:49 +0x1bf fp=0xc82003cde0 sp=0xc82003cca8
runtime.concatstring3(0x0, 0x7f5e434ba9d0, 0x6, 0x7f5e48155490, 0x7f5e4d27dc86, 0x7f5e434ba560, 0x1, 0x0, 0x0)
    /usr/local/go/src/runtime/string.go:63 +0x6c fp=0xc82003ce30 sp=0xc82003cde0
main.Hello(0x7f5e48155490, 0x7f5e4d27dc86)
    /home/vagrant/go/src/github.com/venkatramachandran/lib-sample/sample.go:9 +0x72 fp=0xc82003cec8 sp=0xc82003ce30
main._cgoexpwrap_9f7405a93e67_Hello(0x7f5e48155490, 0x7f5e4d27dc86)
    github.com/venkatramachandran/lib-sample/_obj/_cgo_gotypes.go:48 +0x2d fp=0xc82003cee0 sp=0xc82003cec8
runtime.call32(0x0, 0x7f5e4e4d3ae8, 0x7f5e4e4d3b70, 0x10)
    /usr/local/go/src/runtime/asm_amd64.s:472 +0x40 fp=0xc82003cf08 sp=0xc82003cee0
runtime.cgocallbackg1()
    /usr/local/go/src/runtime/cgocall.go:267 +0x110 fp=0xc82003cf40 sp=0xc82003cf08
runtime.cgocallbackg()
    /usr/local/go/src/runtime/cgocall.go:180 +0xd9 fp=0xc82003cfa0 sp=0xc82003cf40
runtime.cgocallback_gofunc(0x0, 0x0, 0x0)
    /usr/local/go/src/runtime/asm_amd64.s:716 +0x5d fp=0xc82003cfb0 sp=0xc82003cfa0
runtime.goexit()
    /usr/local/go/src/runtime/asm_amd64.s:1998 +0x1 fp=0xc82003cfb8 sp=0xc82003cfb0

goroutine 18 [syscall, locked to thread]:
runtime.goexit()
    /usr/local/go/src/runtime/asm_amd64.s:1998 +0x1
Aborted (core dumped)

出了什么问题？如果我使用int或float作为参数创建方法，则不会发生此错误。

Answer 1

<强>原因：这背后的原因是你的go函数Hello需要一个golang字符串，但是python和Java传递了C style字符串。

<强>解决方案：因为您使用buildmode=c-shared编译了golang库。 Python ctypes包和java JNI将其视为普通的c方法。并传递一个c样式字符串，它实际上只是一个由NULL终止的字符数组。

但是在你的代码中，函数Hello需要一个golang字符串，它的格式与典型的c样式字符串不同。因此这个错误。

可以通过将s声明为*C.char来解决。

更正的计划如下：

// package name: libsample.so
package main

import "C"
import "fmt"

//export Hello
func Hello(s *C.char) {
    fmt.Println("Hello " + C.GoString(s) + "!")
}

func main() {
}

从共享库访问函数时内存不足

1 个答案: