恐慌：运行时错误：cgo结果具有Go指针

huangapple
go评论197阅读模式
英文:

panic: runtime error: cgo result has Go pointer

问题

你好，最近我尝试从Python代码中调用一个打印一些除法结果的Golang函数，该函数使用for循环。以下是recap.go的完整代码：

  1. package main
  3. import (
  4. 	"C"
  5. 	"strconv"
  6. )
  8. //export PrintAlg
  9. func PrintAlg(debug bool) string {
  10. 	var b200 int = 0
  11. 	var b300 int = 0
  12. 	var b400 int = 0
  13. 	var x string = "A"
  14. 	if debug == true {
  15. 		// extra
  16. 	} else if debug == false {
  17. 		for i := 1; i <= 100; i++ {
  18. 			if i%4 == 0 && i%3 == 0 {
  19. 				b200++
  20. 				b300++
  21. 				b400++
  22. 			} else if i%4 == 0 && !(i%3 == 0) {
  23. 				b400++
  24. 				b200++
  25. 			} else if i%2 == 0 && i%3 == 0 && !(i%4 == 0) {
  26. 				b200++
  27. 				b300++
  28. 			} else if i%3 == 0 && !(i%2 == 0) && !(i%4 == 0) {
  29. 				b300++
  30. 			} else if i%2 == 0 && !(i%3 == 0) && !(i%4 == 0) {
  31. 				b200++
  32. 			} else if i%2 == 0 && i%3 == 0 && i%4 == 0 {
  33. 				b200++
  34. 				b300++
  35. 				b400++
  36. 			}
  37. 		}
  38. 		x = strconv.Itoa(b200) + " " + strconv.Itoa(b300) + " " + strconv.Itoa(b400)
  39. 	}
  40. 	return x
  41. }
  43. func main() {
  45. }

然后，我尝试使用CTYPES（在Python代码中）调用PrintAlg函数。当我从命令行运行Python代码时，出现了以下错误：

  1. panic: runtime error: cgo result has Go pointer
  2. goroutine 17 [running, locked to thread]:
  3. panic({0x67322a80, 0xc00004a0a0})
  4. C:/Program Files/Go/src/runtime/panic.go:1147 +0x3a8
  5. runtime.cgoCheckArg(0x67320da0, 0xc00004a090, 0x10, 0x0, {0x6732cc4f, 0x19})
  6. C:/Program Files/Go/src/runtime/cgocall.go:514 +0x4d8
  7. runtime.cgoCheckResult({0x67320da0, 0xc00004a090})
  8. C:/Program Files/Go/src/runtime/cgocall.go:630 +0x54
  9. _cgoexp_ba17693967af_PrintAlg(0x108efee9c0)
  10. _cgo_gotypes.go:39 +0x5a
  11. runtime.cgocallbackg1(0x67315640, 0x0, 0x0)
  12. C:/Program Files/Go/src/runtime/cgocall.go:306 +0x29a
  13. runtime.cgocallbackg(0x0, 0x0, 0x0)
  14. C:/Program Files/Go/src/runtime/cgocall.go:232 +0x106
  15. runtime.cgocallbackg(0x67315640, 0x108efee9c0, 0x0)
  16. &lt;autogenerated&gt;:1 +0x36
  17. runtime.cgocallback(0x0, 0x0, 0x0)
  18. C:/Program Files/Go/src/runtime/asm_amd64.s:915 +0xd7
  19. runtime.goexit()
  20. C:/Program Files/Go/src/runtime/asm_amd64.s:1581 +0x1

你可以如何修复这个错误？

英文:

Hello i was recently trying to call a golang function from python code that is printing some division things with for loop.

Full code of recap.go:

  1. package main
  3. import (
  4. 	&quot;C&quot;
  5. 	&quot;strconv&quot;
  6. )
  8. //export PrintAlg
  9. func PrintAlg(debug bool) string {
  10. 	var b200 int = 0
  11. 	var b300 int = 0
  12. 	var b400 int = 0
  13. 	var x string = &quot;A&quot;
  14. 	if debug == true {
  15. 		// extra
  16. 	} else if debug == false {
  17. 		for i := 1; i &lt;= 100; i++ {
  18. 			if i%4 == 0 &amp;&amp; i%3 == 0 {
  19. 				b200++
  20. 				b300++
  21. 				b400++
  22. 			} else if i%4 == 0 &amp;&amp; !(i%3 == 0) {
  23. 				b400++
  24. 				b200++
  25. 			} else if i%2 == 0 &amp;&amp; i%3 == 0 &amp;&amp; !(i%4 == 0) {
  26. 				b200++
  27. 				b300++
  28. 			} else if i%3 == 0 &amp;&amp; !(i%2 == 0) &amp;&amp; !(i%4 == 0) {
  29. 				b300++
  30. 			} else if i%2 == 0 &amp;&amp; !(i%3 == 0) &amp;&amp; !(i%4 == 0) {
  31. 				b200++
  32. 			} else if i%2 == 0 &amp;&amp; i%3 == 0 &amp;&amp; i%4 == 0 {
  33. 				b200++
  34. 				b300++
  35. 				b400++
  36. 			}
  37. 		}
  38. 		x = strconv.Itoa(b200) + &quot; &quot; + strconv.Itoa(b300) + &quot; &quot; + strconv.Itoa(b400)
  39. 	}
  40. 	return x
  41. }
  43. func main() {
  45. }

then i tryed to call PrintAlg function with CTYPES (in python code). Then when i ran the python code from cmd, this error occured:

  1. panic: runtime error: cgo result has Go pointer
  2. goroutine 17 [running, locked to thread]:
  3. panic({0x67322a80, 0xc00004a0a0})
  4. C:/Program Files/Go/src/runtime/panic.go:1147 +0x3a8
  5. runtime.cgoCheckArg(0x67320da0, 0xc00004a090, 0x10, 0x0, {0x6732cc4f, 0x19})
  6. C:/Program Files/Go/src/runtime/cgocall.go:514 +0x4d8
  7. runtime.cgoCheckResult({0x67320da0, 0xc00004a090})
  8. C:/Program Files/Go/src/runtime/cgocall.go:630 +0x54
  9. _cgoexp_ba17693967af_PrintAlg(0x108efee9c0)
  10. _cgo_gotypes.go:39 +0x5a
  11. runtime.cgocallbackg1(0x67315640, 0x0, 0x0)
  12. C:/Program Files/Go/src/runtime/cgocall.go:306 +0x29a
  13. runtime.cgocallbackg(0x0, 0x0, 0x0)
  14. C:/Program Files/Go/src/runtime/cgocall.go:232 +0x106
  15. runtime.cgocallbackg(0x67315640, 0x108efee9c0, 0x0)
  16. &lt;autogenerated&gt;:1 +0x36
  17. runtime.cgocallback(0x0, 0x0, 0x0)
  18. C:/Program Files/Go/src/runtime/asm_amd64.s:915 +0xd7
  19. runtime.goexit()
  20. C:/Program Files/Go/src/runtime/asm_amd64.s:1581 +0x1

what can i do for fixing this error?

答案1

得分: 1

Go运行时对字符串的实现是：

  1. type stringStruct struct {
  2.     str unsafe.Pointer
  3.     len int
  4. }

当你从Go的PrintAlg函数中返回时，即return x，Go会返回一个指向Go字符串x底层字节的Go内存实例stringStruct。

  1. panic: runtime error: cgo result has Go pointer

阅读cgo文档，特别是Passing_pointers部分，了解详情。

在Go中，可以这样编写：

  1. func PrintAlg(debug bool) *C.char {
  2.     // ...
  3.     return C.CString(x)
  4. }

以返回一个指向C字符串实例的指针。在不再需要时释放指针。

  1. $ go build -buildmode=c-shared -o _recap.so
  2. $ python3 recap.py
  3. 50 33 25
  4. $

recap.go:

  1. package main
  3. import (
  4.     "C"
  5.     "strconv"
  6. )
  8. //export PrintAlg
  9. func PrintAlg(debug bool) *C.char {
  10.     var b200 int = 0
  11.     var b300 int = 0
  12.     var b400 int = 0
  13.     var x string = "A"
  14.     if debug == true {
  15.         // extra
  16.     } else if debug == false {
  17.         for i := 1; i <= 100; i++ {
  18.             if i%4 == 0 && i%3 == 0 {
  19.                 b200++
  20.                 b300++
  21.                 b400++
  22.             } else if i%4 == 0 && !(i%3 == 0) {
  23.                 b400++
  24.                 b200++
  25.             } else if i%2 == 0 && i%3 == 0 && !(i%4 == 0) {
  26.                 b200++
  27.                 b300++
  28.             } else if i%3 == 0 && !(i%2 == 0) && !(i%4 == 0) {
  29.                 b300++
  30.             } else if i%2 == 0 && !(i%3 == 0) && !(i%4 == 0) {
  31.                 b200++
  32.             } else if i%2 == 0 && i%3 == 0 && i%4 == 0 {
  33.                 b200++
  34.                 b300++
  35.                 b400++
  36.             }
  37.         }
  38.         x = strconv.Itoa(b200) + " " + strconv.Itoa(b300) + " " + strconv.Itoa(b400)
  39.     }
  40.     return C.CString(x)
  41. }
  43. func main() {}

recap.py:

  1. import ctypes
  2. recap = ctypes.cdll.LoadLibrary('./_recap.so')
  3. printAlg = recap.PrintAlg
  4. printAlg.argtypes = [ctypes.c_bool]
  5. printAlg.restype = ctypes.c_void_p
  6. free = recap.free
  7. free.argtypes = [ctypes.c_void_p]
  8. px = printAlg(False)
  9. x = ctypes.string_at(px).decode('utf-8')
  10. free(px)
  11. print(x)
英文:

The Go runtime implementation of a string is

  1. type stringStruct struct {
  2. str unsafe.Pointer
  3. len int
  4. }

When you return from your Go PrintAlg function - return x - Go returns a Go memory instance of stringStruct which points to the underlying bytes of the Go string x.

  1. panic: runtime error: cgo result has Go pointer

Read the cgo documentation, especially Passing_pointers, for details.

In Go, write

  1. func PrintAlg(debug bool) *C.char {
  2. // ...
  3. return C.CString(x)
  4. }

to return a pointer to an instance of a C string. Free the pointer when no longer needed.

  1. $ go build -buildmode=c-shared -o _recap.so
  2. $ python3 recap.py
  3. 50 33 25
  4. $

recap.go:

  1. package main
  2. import (
  3. &quot;C&quot;
  4. &quot;strconv&quot;
  5. )
  6. //export PrintAlg
  7. func PrintAlg(debug bool) *C.char {
  8. var b200 int = 0
  9. var b300 int = 0
  10. var b400 int = 0
  11. var x string = &quot;A&quot;
  12. if debug == true {
  13. // extra
  14. } else if debug == false {
  15. for i := 1; i &lt;= 100; i++ {
  16. if i%4 == 0 &amp;&amp; i%3 == 0 {
  17. b200++
  18. b300++
  19. b400++
  20. } else if i%4 == 0 &amp;&amp; !(i%3 == 0) {
  21. b400++
  22. b200++
  23. } else if i%2 == 0 &amp;&amp; i%3 == 0 &amp;&amp; !(i%4 == 0) {
  24. b200++
  25. b300++
  26. } else if i%3 == 0 &amp;&amp; !(i%2 == 0) &amp;&amp; !(i%4 == 0) {
  27. b300++
  28. } else if i%2 == 0 &amp;&amp; !(i%3 == 0) &amp;&amp; !(i%4 == 0) {
  29. b200++
  30. } else if i%2 == 0 &amp;&amp; i%3 == 0 &amp;&amp; i%4 == 0 {
  31. b200++
  32. b300++
  33. b400++
  34. }
  35. }
  36. x = strconv.Itoa(b200) + &quot; &quot; + strconv.Itoa(b300) + &quot; &quot; + strconv.Itoa(b400)
  37. }
  38. return C.CString(x)
  39. }
  40. func main() {}

recap.py:

  1. import ctypes
  2. recap = ctypes.cdll.LoadLibrary(&#39;./_recap.so&#39;)
  3. printAlg = recap.PrintAlg
  4. printAlg.argtypes = [ctypes.c_bool]
  5. printAlg.restype = ctypes.c_void_p
  6. free = recap.free
  7. free.argtypes = [ctypes.c_void_p]
  8. px = printAlg(False)
  9. x = ctypes.string_at(px).decode(&#39;utf-8&#39;)
  10. free(px)
  11. print(x)

huangapple
  • 本文由 发表于 2022年3月12日 21:16:22
  • 转载请务必保留本文链接：https://go.coder-hub.com/71450016.html
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