如何使用cgo将C语言的“hello world”程序包装到argv中？

huangapple
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英文:

How to wrap a C "hello world" with argv using cgo?

问题

考虑以下的hello.c代码：

  1. #include <stdio.h>
  2. int main(int argc, char* argv[]) {
  3.     printf("Hello, world! argv[0]=%s\n", argv[0]);
  4. }

Makefile文件只包含一行代码：all: hello。我该如何将这个函数包装（并编译）到一个Go程序中，就像这个（不工作的）示例中一样？

  1. package main
  2. // int main(int argc, char* argv[]);
  3. import "C"
  4. func main() {
  5.     argc := C.int(1)
  6.     argv := make([]*C.char, 1)
  7.     argv[0] = C.CString("hai")
  8.     C.main(argc, &argv[0])
  9. }

我得到的错误是：

  1. (virtualenv)[14:16:21][/tmp/cgo]$ ./main 
  2. fatal error: unexpected signal during runtime execution
  3. [signal 0xb code=0x1 addr=0x1c000000000 pc=0x41d563]
  5. runtime stack:
  6. runtime.throw(0x48b400, 0x2a)
  7.  /usr/lib/golang/src/runtime/panic.go:527 +0x90
  8. runtime.sigpanic()
  9.  /usr/lib/golang/src/runtime/sigpanic_unix.go:12 +0x5a
  10. runtime.mHeap_Grow(0x6c7c20, 0x8, 0x0)
  11.  /usr/lib/golang/src/runtime/mheap.go:647 +0x243
  12. runtime.mHeap_AllocSpanLocked(0x6c7c20, 0x1, 0x0)
  13.  /usr/lib/golang/src/runtime/mheap.go:532 +0x5f1
  14. runtime.mHeap_Alloc_m(0x6c7c20, 0x1, 0x15, 0x0)
  15.  /usr/lib/golang/src/runtime/mheap.go:425 +0x1ac
  16. runtime.mHeap_Alloc.func1()
  17.  /usr/lib/golang/src/runtime/mheap.go:484 +0x41
  18. runtime.systemstack(0x7ffcb3aab958)
  19.  /usr/lib/golang/src/runtime/asm_amd64.s:278 +0xab
  20. runtime.mHeap_Alloc(0x6c7c20, 0x1, 0x10000000015, 0x40a954)
  21.  /usr/lib/golang/src/runtime/mheap.go:485 +0x63
  22. runtime.mCentral_Grow(0x6d0898, 0x0)
  23.  /usr/lib/golang/src/runtime/mcentral.go:190 +0x93
  24. runtime.mCentral_CacheSpan(0x6d0898, 0x6c1180)
  25.  /usr/lib/golang/src/runtime/mcentral.go:86 +0x4d4
  26. runtime.mCache_Refill(0x7fbc9971d050, 0x15, 0x40ca28)
  27.  /usr/lib/golang/src/runtime/mcache.go:118 +0xcf
  28. runtime.mallocgc.func2()
  29.  /usr/lib/golang/src/runtime/malloc.go:611 +0x2b
  30. runtime.systemstack(0x7ffcb3aabb28)
  31.  /usr/lib/golang/src/runtime/asm_amd64.s:278 +0xab
  32. runtime.mallocgc(0x180, 0x476220, 0x0, 0x800000000)
  33.  /usr/lib/golang/src/runtime/malloc.go:612 +0x842
  34. runtime.newobject(0x476220, 0x6c0c40)
  35.  /usr/lib/golang/src/runtime/malloc.go:760 +0x42
  36. runtime.malg(0x8000, 0x6c0e40)
  37.  /usr/lib/golang/src/runtime/proc1.go:2188 +0x27
  38. runtime.mpreinit(0x6c1180)
  39.  /usr/lib/golang/src/runtime/os1_linux.go:197 +0x1f
  40. runtime.mcommoninit(0x6c1180)
  41.  /usr/lib/golang/src/runtime/proc1.go:114 +0x100
  42. runtime.schedinit()
  43.  /usr/lib/golang/src/runtime/proc1.go:57 +0x79
  44. runtime.rt0_go(0xc82002e008, 0x1, 0xc82002e008, 0x1, 0x40122a, 0xc82004fef8, 0x0, 0x8, 0x44fbaa, 0xc82004fe80, ...)
  45.  /usr/lib/golang/src/runtime/asm_amd64.s:109 +0x132
  47. goroutine 1 [syscall, locked to thread]:
  48. runtime.cgocall(0x401210, 0xc82004fef8, 0x0)
  49.  /usr/lib/golang/src/runtime/cgocall.go:120 +0x11b fp=0xc82004feb0 sp=0xc82004fe80
  50. main._Cfunc_main(0x1, 0xc82002e008, 0x0)
  51.  command-line-arguments/_obj/_cgo_gotypes.go:49 +0x39 fp=0xc82004fef8 sp=0xc82004feb0
  52. main.main()
  53.  /tmp/cgo/main.go:8 +0xb4 fp=0xc82004ff50 sp=0xc82004fef8
  54. runtime.main()
  55.  /usr/lib/golang/src/runtime/proc.go:111 +0x2b0 fp=0xc82004ffa0 sp=0xc82004ff50
  56. runtime.goexit()
  57.  /usr/lib/golang/src/runtime/asm_amd64.s:1696 +0x1 fp=0xc82004ffa8 sp=0xc82004ffa0
  59. goroutine 17 [syscall, locked to thread]:
  60. runtime.goexit()
  61.  /usr/lib/golang/src/runtime/asm_amd64.s:1696 +0x1
英文:

Consider the following hello.c:

  1. #include &lt;stdio.h&gt;
  2. int main(int argc, char* argv[]) {
  3.     printf(&quot;Hello, world! argv[0]=%s\n&quot;, argv[0]);
  4. }

Makefile only contains one line: all: hello. How can I wrap (and compile) this function around a Go program, like in this (non-working) example?

  1. package main
  2. // int main(int argc, char* argv[]);
  3. import &quot;C&quot;
  4. func main() {
  5. argc := C.int(1);
  6. argv := make([]*C.char, 1)
  7. argv[0] = C.CString(&quot;hai&quot;);
  8. C.main(argc, &amp;argv[0])
  9. }

The error I'm getting is:

  1. (virtualenv)[14:16:21][/tmp/cgo]$ ./main 
  2. fatal error: unexpected signal during runtime execution
  3. [signal 0xb code=0x1 addr=0x1c000000000 pc=0x41d563]
  5. runtime stack:
  6. runtime.throw(0x48b400, 0x2a)
  7.  /usr/lib/golang/src/runtime/panic.go:527 +0x90
  8. runtime.sigpanic()
  9.  /usr/lib/golang/src/runtime/sigpanic_unix.go:12 +0x5a
  10. runtime.mHeap_Grow(0x6c7c20, 0x8, 0x0)
  11.  /usr/lib/golang/src/runtime/mheap.go:647 +0x243
  12. runtime.mHeap_AllocSpanLocked(0x6c7c20, 0x1, 0x0)
  13.  /usr/lib/golang/src/runtime/mheap.go:532 +0x5f1
  14. runtime.mHeap_Alloc_m(0x6c7c20, 0x1, 0x15, 0x0)
  15.  /usr/lib/golang/src/runtime/mheap.go:425 +0x1ac
  16. runtime.mHeap_Alloc.func1()
  17.  /usr/lib/golang/src/runtime/mheap.go:484 +0x41
  18. runtime.systemstack(0x7ffcb3aab958)
  19.  /usr/lib/golang/src/runtime/asm_amd64.s:278 +0xab
  20. runtime.mHeap_Alloc(0x6c7c20, 0x1, 0x10000000015, 0x40a954)
  21.  /usr/lib/golang/src/runtime/mheap.go:485 +0x63
  22. runtime.mCentral_Grow(0x6d0898, 0x0)
  23.  /usr/lib/golang/src/runtime/mcentral.go:190 +0x93
  24. runtime.mCentral_CacheSpan(0x6d0898, 0x6c1180)
  25.  /usr/lib/golang/src/runtime/mcentral.go:86 +0x4d4
  26. runtime.mCache_Refill(0x7fbc9971d050, 0x15, 0x40ca28)
  27.  /usr/lib/golang/src/runtime/mcache.go:118 +0xcf
  28. runtime.mallocgc.func2()
  29.  /usr/lib/golang/src/runtime/malloc.go:611 +0x2b
  30. runtime.systemstack(0x7ffcb3aabb28)
  31.  /usr/lib/golang/src/runtime/asm_amd64.s:278 +0xab
  32. runtime.mallocgc(0x180, 0x476220, 0x0, 0x800000000)
  33.  /usr/lib/golang/src/runtime/malloc.go:612 +0x842
  34. runtime.newobject(0x476220, 0x6c0c40)
  35.  /usr/lib/golang/src/runtime/malloc.go:760 +0x42
  36. runtime.malg(0x8000, 0x6c0e40)
  37.  /usr/lib/golang/src/runtime/proc1.go:2188 +0x27
  38. runtime.mpreinit(0x6c1180)
  39.  /usr/lib/golang/src/runtime/os1_linux.go:197 +0x1f
  40. runtime.mcommoninit(0x6c1180)
  41.  /usr/lib/golang/src/runtime/proc1.go:114 +0x100
  42. runtime.schedinit()
  43.  /usr/lib/golang/src/runtime/proc1.go:57 +0x79
  44. runtime.rt0_go(0xc82002e008, 0x1, 0xc82002e008, 0x1, 0x40122a, 0xc82004fef8, 0x0, 0x8, 0x44fbaa, 0xc82004fe80, ...)
  45.  /usr/lib/golang/src/runtime/asm_amd64.s:109 +0x132
  47. goroutine 1 [syscall, locked to thread]:
  48. runtime.cgocall(0x401210, 0xc82004fef8, 0x0)
  49.  /usr/lib/golang/src/runtime/cgocall.go:120 +0x11b fp=0xc82004feb0 sp=0xc82004fe80
  50. main._Cfunc_main(0x1, 0xc82002e008, 0x0)
  51.  command-line-arguments/_obj/_cgo_gotypes.go:49 +0x39 fp=0xc82004fef8 sp=0xc82004feb0
  52. main.main()
  53.  /tmp/cgo/main.go:8 +0xb4 fp=0xc82004ff50 sp=0xc82004fef8
  54. runtime.main()
  55.  /usr/lib/golang/src/runtime/proc.go:111 +0x2b0 fp=0xc82004ffa0 sp=0xc82004ff50
  56. runtime.goexit()
  57.  /usr/lib/golang/src/runtime/asm_amd64.s:1696 +0x1 fp=0xc82004ffa8 sp=0xc82004ffa0
  59. goroutine 17 [syscall, locked to thread]:
  60. runtime.goexit()
  61.  /usr/lib/golang/src/runtime/asm_amd64.s:1696 +0x1

答案1

得分: 8

当我使用go run main.go时，得到的结果与你一样，但是当我使用go build .时，得到了一个更好的错误信息：

  1. /tmp/go-build887090083/cgoSO/_obj/hello.o: In function `main&#39;:
  2. /usr/include/x86_64-linux-gnu/bits/stdio2.h:104: multiple definition of `main&#39;
  3. /tmp/go-build887090083/cgoSO/_obj/_cgo_main.o:/tmp/go-build887090083/cgoSO/_obj/_cgo_main.c:1: first defined here
  4. collect2: error: ld returned 1 exit status

然后我在go build命令中添加了-work标志，以保留临时工作空间，并且这是/tmp/go-build465152107/cgoSO/_obj/_cgo_main.c的内容：

  1. int main() { return 0; }
  2. void crosscall2(void(*fn)(void*, int), void *a, int c) { }
  3. void _cgo_wait_runtime_init_done() { }
  4. char* _cgo_topofstack(void) { return (char*)0; }
  5. void _cgo_allocate(void *a, int c) { }
  6. void _cgo_panic(void *a, int c) { }
  7. void _cgo_reginit(void) { }

第一行是在这里写的：https://github.com/golang/go/blob/f2e4c8b5fb3660d793b2c545ef207153db0a34b1/src/cmd/cgo/out.go#L49

并且没有条件，所以无法避免。

结论：你不能导入一个C程序，你只能导入库（这实际上是有道理的）。

如果这个C程序是你自己的代码，那么只需将main改为其他任何名称，它就会工作。

英文:

I get the same result when using go run main.go, but when using go build ., you get a better error:

  1. /tmp/go-build887090083/cgoSO/_obj/hello.o: In function `main&#39;:
  2. /usr/include/x86_64-linux-gnu/bits/stdio2.h:104: multiple definition of `main&#39;
  3. /tmp/go-build887090083/cgoSO/_obj/_cgo_main.o:/tmp/go-build887090083/cgoSO/_obj/_cgo_main.c:1: first defined here
  4. collect2: error: ld returned 1 exit status

I then added the -work flag to go build to persist the tmp workspace, and here is the content of /tmp/go-build465152107/cgoSO/_obj/_cgo_main.c:

  1. int main() { return 0; }
  2. void crosscall2(void(*fn)(void*, int), void *a, int c) { }
  3. void _cgo_wait_runtime_init_done() { }
  4. char* _cgo_topofstack(void) { return (char*)0; }
  5. void _cgo_allocate(void *a, int c) { }
  6. void _cgo_panic(void *a, int c) { }
  7. void _cgo_reginit(void) { }

That first line is written there: https://github.com/golang/go/blob/f2e4c8b5fb3660d793b2c545ef207153db0a34b1/src/cmd/cgo/out.go#L49

And there is no conditions, so it cannot be avoided.

Conclusion: You cannot import a C program, you can only import libraries (it actually makes sense).

If the C is your code, then just change main for anything else and it will work.

huangapple
  • 本文由 发表于 2015年10月19日 19:14:21
  • 转载请务必保留本文链接：https://go.coder-hub.com/33212939.html
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