如何释放不安全。在 cgo 中使用包装器的指针？

Question

我该如何创建一个包装器来释放不安全的人。指针在我的代码中？这是我的 cgo 代码：//export clientpyfunc clientpy(url *C.char, headersfrompy *C.char, proxy *C.char) unsafe.Pointer {    s := C.GoString(url)    headers := C.GoString(headersfrompy)    p := C.GoString(proxy)    request := UrlGet(s, headers, p)    length := make([]byte, 8)    binary.LittleEndian.PutUint64(length, uint64(len(request)))    return C.CBytes(append(length, request...))}//export FreeCBytefunc FreeCByte(b *unsafe.Pointer) {    C.free(unsafe.Pointer(b))}似乎我无法释放python代码中的内存。我正在创建一个包装器，以便我可以在python中释放内存，而不是在go内部释放内存，这样我就不会有悬空的指针。这是我的蟒蛇代码：from ctypes import cdllimport ctypes, cchardet, jsonfrom bs4 import BeautifulSouplib = cdll.LoadLibrary("./test.so")lib.cclientpy.argtypes = [ctypes.c_char_p, ctypes.c_char_p, ctypes.c_char_p]lib.cclientpy.restype = ctypes.POINTER(ctypes.c_ubyte * 8)""" THERE IS A BIG MEMORY LEAK, BEWARE """free = lib.freefree.argtypes = [ctypes.POINTER(ctypes.c_ubyte * 8)]def newrequest(path, lister={}, proxy=[]):    try:        print(f"proxy: {proxy}")        ptr = lib.cclientpy(path.encode("utf-8"), str(lister).encode("utf-8"), str(proxy).encode("utf-8"))        length = int.from_bytes(ptr.contents, byteorder="little")        data = bytes(ctypes.cast(ptr,                                 ctypes.POINTER(ctypes.c_ubyte * (8 + length))                                 ).contents[8:])        #free(ptr)        lib.FreeCByte(ptr)        print(f'bytes: {bytes(ctypes.cast(ptr,ctypes.POINTER(ctypes.c_ubyte * (8 + length))).contents[8:])}')        return data    except:        pass如何释放不安全的指针？

Answer 1

释放 Go 中的，而不是指向 的指针。unsafe.Pointerunsafe.Pointer

//export FreeCByte

func FreeCByte(b unsafe.Pointer) {

    C.free(b)

}

评论：我仍然收到内存泄漏。– 乔顿

问题中的代码无法编译和运行。我修复了您的代码以进行编译和运行，并添加了一些调试代码。显然，内存正在被释放。

$ go version

go version devel go1.18-8214257347 Wed Sep 8 14:51:40 2021 +0000 linux/amd64

$ go build -o test.so -buildmode=c-shared test.go

$ python3 --version

Python 3.9.5

$ python3 test.py

proxy: []

Go: cclientpy: C.CBytes: 0x1a7e420

Go: FreeCByte: 0x1a7e420

Go: FreeCByte: double free 0x1a7e420

free(): double free detected in tcache 2

Aborted (core dumped)

$ 

$ cat test.go

package main

import (

    "encoding/binary"

    "fmt"

    "os"

    "unsafe"

)

/*

#include <stdlib.h>

*/

import "C"

func UrlGet(s, headers, p string) []byte {

    return nil

}

const debug = true

//export cclientpy

func cclientpy(url *C.char, headersfrompy *C.char, proxy *C.char) unsafe.Pointer {

    s := C.GoString(url)

    headers := C.GoString(headersfrompy)

    p := C.GoString(proxy)

    request := UrlGet(s, headers, p)

    length := make([]byte, 8)

    binary.LittleEndian.PutUint64(length, uint64(len(request)))

    cbytes := C.CBytes(append(length, request...))

    if debug {

        fmt.Fprintln(os.Stderr, "Go: cclientpy: C.CBytes:", cbytes)

    }

    return cbytes

}

//export FreeCByte

func FreeCByte(b unsafe.Pointer) {

    if debug {

        fmt.Fprintln(os.Stderr, "Go: FreeCByte:", b)

    }

    C.free(b)

    if debug {

        // tests to see if already freed, should fail

        // free(): double free detected in tcache 2

        // Aborted (core dumped)

        fmt.Fprintln(os.Stderr, "Go: FreeCByte: double free", b)

        C.free(b)

    }

}

func main() {}

$ 

$ cat test.py

from ctypes import cdll

import ctypes, chardet as cchardet, json

from bs4 import BeautifulSoup

lib = cdll.LoadLibrary("./test.so")

lib.cclientpy.argtypes = [ctypes.c_char_p, ctypes.c_char_p, ctypes.c_char_p]

lib.cclientpy.restype = ctypes.POINTER(ctypes.c_ubyte * 8)

""" THERE IS A BIG MEMORY LEAK, BEWARE """

free = lib.free

free.argtypes = [ctypes.POINTER(ctypes.c_ubyte * 8)]

def newrequest(path, lister={}, proxy=[]):

    try:

        print(f"proxy: {proxy}")

        ptr = lib.cclientpy(path.encode("utf-8"), str(lister).encode("utf-8"), str(proxy).encode("utf-8"))

        length = int.from_bytes(ptr.contents, byteorder="little")

        data = bytes(ctypes.cast(ptr,

                                 ctypes.POINTER(ctypes.c_ubyte * (8 + length))

                                 ).contents[8:])

        #free(ptr)

        lib.FreeCByte(ptr)

        print(f'bytes: {bytes(ctypes.cast(ptr,ctypes.POINTER(ctypes.c_ubyte * (8 + length))).contents[8:])}')

        return data

    except:

        pass

    

newrequest(path='argpath', lister={}, proxy=[])

$