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【go/方法记录】cgo静态库编译以及使用dlv定位cgo崩溃问题

article 2024/9/22 9:10:53

目录

  • 说在前面
  • 文件树
  • 静态库编译
  • cgo使用
  • 崩溃模拟
  • 使用dlv定位崩溃
  • 参考

说在前面

  • 测试环境：WSL2
  • go版本：go version go1.23.1 linux/amd64
  • gcc版本：gcc (Ubuntu 11.4.0-1ubuntu1~22.04) 11.4.0
  • cmake版本：3.22.1

文件树

├── buffer # go package
│   ├── buffer.go
│   ├── buffer_go.h
│   └── libbuffer.a
├── c # c/c++源代码
│   ├── CMakeLists.txt # cmake
│   ├── buffer # c/c++源代码
│   │   ├── buffer.h
│   │   ├── buffer_go.cpp
│   │   └── buffer_go.h
│   ├── lib # 静态库目录
│   │   └── libbuffer.a
│   └── main.cpp
└── main.go

静态库编译

  • 这部分和go无关，按照正常的静态库编译走就行，这里我使用cmake进行编译
  • buffer.h
    #ifndef __BUFFER_H__
#define __BUFFER_H__
#include <string>

struct Buffer {
    std::string* s_;

    Buffer(int size) {
        this->s_ = new std::string(size, char('\0'));
    }
    ~Buffer() {
        delete this->s_;
    }

    int Size() const {
        return this->s_->size();
    }
    char* Data() {
        return (char*)this->s_->data();
    }
};

#endif
  • 然后我们需要对其进行封装，这部分可以参考这里
  • buffer_go.h
    #define DLLIMPORT

#ifdef __cplusplus
extern "C" {
#endif

typedef struct Buffer_T Buffer_T;

Buffer_T* NewBuffer(int size);
void DeleteBuffer(Buffer_T* p);
int BufferSize(Buffer_T* p);

#ifdef __cplusplus
}
#endif
  • buffer_go.cpp
    #include "buffer.h"
#include "buffer_go.h"

#ifdef __cplusplus
extern "C" {
#endif

struct Buffer_T: Buffer {
    Buffer_T(int size): Buffer(size) {}
    ~Buffer_T() {}
};

DLLIMPORT Buffer_T* NewBuffer(int size) {
    auto p = new Buffer_T(size);
    return p;
}

DLLIMPORT void DeleteBuffer(Buffer_T* p) {
    delete p;
}

DLLIMPORT int BufferSize(Buffer_T* p) {
    return p->Size();
}

#ifdef __cplusplus
}
#endif
  • 然后就是cmake
    cmake_minimum_required(VERSION 3.2)
project(Buffer)
set(CMAKE_BUILD_TYPE "RELEASE")
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")

# 设置编译后库文件目录
set(LIBRARY_OUTPUT_PATH ${PROJECT_SOURCE_DIR}/lib)

include_directories(${PROJECT_SOURCE_DIR}/buffer)
# 添加编译可执行文件
aux_source_directory(${PROJECT_SOURCE_DIR}/buffer SRC)

add_library(buffer STATIC ${SRC})
add_executable(buffer_exe
        main.cpp
        )

# 链接主程序
target_link_libraries(buffer_exe
        PRIVATE
        buffer
        )
  • 执行编译
    cd ./c
cmake .
make
    动态库将生成在目录./c/lib

cgo使用

  • 首先将buffer_go.h、libbuffer.a拷贝到./buffer目录下，并创建buffer.go文件。注意，以下注释中的#include "buffer_go.h"和import "C"不要有空行
  • buffer.go
    package buffer

// #cgo CFLAGS: -I.
// #cgo CXXFLAGS: -std=c++11
// #cgo LDFLAGS: -L./ -lbuffer -lstdc++
//
// #include "buffer_go.h"
import "C"

type BufferT C.Buffer_T

func NewBuffer(size int) *BufferT {
	p := C.NewBuffer(C.int(size))
	return (*BufferT)(p)
}

func DeleteBuffer(p *BufferT) {
	C.DeleteBuffer((*C.Buffer_T)(p))
}

func BufferSize(p *BufferT) C.int {
	return C.BufferSize((*C.Buffer_T)(p))
}
  • 然后是main.go
    package main

import (
	"fmt"
)

func main() {
	b := buffer.NewBuffer(2)
	fmt.Println(buffer.BufferSize(b))
	buffer.DeleteBuffer(b)
}
  • 执行程序输出
    ~/cgotest$ go run main.go
2

崩溃模拟

  • 正常go中的崩溃，例如空指针调用等是可以通过recover处理的，例如

    func main() {

	go func() {
		defer func() {
			if err := recover(); err != nil {
				fmt.Println("err: ", string(debug.Stack()))
			}
		}()

		time.Sleep(5 * time.Second)

		var b uint32
		var a uint32

		_ = b / a
	}()

	var i int
	for {
		time.Sleep(time.Second)

		i++
		fmt.Println(i)
	}
}

    可以看到进程可以继续运行

    ~/cgotest$ go run main.go
1
2
3
4
err:  goroutine 18 [running]:
runtime/debug.Stack()
        /usr/local/go/src/runtime/debug/stack.go:26 +0x5e
main.main.func1.1()
        /home/xx/cgotest/main.go:14 +0x2a
panic({0x49cb60?, 0x54d840?})
        /usr/local/go/src/runtime/panic.go:785 +0x132
main.main.func1()
        /home/xx/cgotest/main.go:23 +0x3f
created by main.main in goroutine 1
        /home/xx/cgotest/main.go:11 +0x1a

5
6

  • 而对于cgo中的崩溃，目前go是没法进行recover的，会导致进程直接崩溃

    package main

import (
	"cgotest/cgotest/buffer"
	"fmt"
	"runtime/debug"
	"time"
)

func main() {

	go func() {
		defer func() {
			if err := recover(); err != nil {
				fmt.Println("err: ", string(debug.Stack()))
			}
		}()

		time.Sleep(5 * time.Second)
		b := buffer.NewBuffer(2)
		buffer.DeleteBuffer(b)

		b = nil
		fmt.Println(buffer.BufferSize(b))
	}()

	var i int
	for {
		time.Sleep(time.Second)

		i++
		fmt.Println(i)
	}
}

    ~/cgotest$ go run main.go
1
2
3
4
SIGSEGV: segmentation violation
PC=0x4930b4 m=5 sigcode=1 addr=0x0
signal arrived during cgo execution

goroutine 6 gp=0xc000007dc0 m=5 mp=0xc000100008 [syscall]:
runtime.cgocall(0x492550, 0xc000076750)

goroutine 6 gp=0xc000007dc0 m=5 mp=0xc000100008 [syscall]:
runtime.cgocall(0x492550, 0xc000076750)
        /usr/local/go/src/runtime/cgocall.go:167 +0x4b fp=0xc000076728 sp=0xc0000766f0 pc=0x462f8b
cgotest/cgotest/buffer._Cfunc_BufferSize(0x0)
        _cgo_gotypes.go:52 +0x47 fp=0xc000076750 sp=0xc000076728 pc=0x475b87
main.main.func1.BufferSize.3(0x0)
        /home/xx/cgotest/buffer/buffer.go:22 +0x3b fp=0xc000076788 sp=0xc000076750 pc=0x4923fb
cgotest/cgotest/buffer.BufferSize(...)
        /home/xx/cgotest/buffer/buffer.go:22
main.main.func1()
        /home/xx/cgotest/main.go:29 +0x6c fp=0xc0000767e0 sp=0xc000076788 pc=0x49234c
runtime.goexit({})
        /usr/local/go/src/runtime/asm_amd64.s:1700 +0x1 fp=0xc0000767e8 sp=0xc0000767e0 pc=0x46e601
created by main.main in goroutine 1
        /home/xx/cgotest/main.go:12 +0x1a

  • 可以看到进程退出并输出了堆栈信息

使用dlv定位崩溃

  • 虽然崩溃时的堆栈信息有标准输出，但是有时标准输出中的堆栈信息可能会被覆盖掉，少了最前面的信息，这个时候可以开启coredump并使用dlv来定位
  • 启用coredump
    ulimit -c unlimited
GOTRACEBACK=crash go run main.go
    在进程崩溃后会生成coredump文件
  • 查看coredump文件目录
    ~/cgotest$ cat /proc/sys/kernel/core_pattern
/mnt/wslg/dumps/core.%e
    可以看到文件生成在/mnt/wslg/dumps/
    ~/cgotest$ ll /mnt/wslg/dumps/
total 6684
-rw------- 1 le   le   83562496 Sep 21 16:04 core.main
  • 安装dlv
    go install github.com/go-delve/delve/cmd/dlv@latest
    可以在gopath文件夹下找到
    ~/cgotest$ /home/xx/go/bin/
dlv          gopls        staticcheck
  • 使用
    # dlv core 二进制程序 coredump文件
~/go/bin/dlv core cgotest /mnt/wslg/dumps/core.main
    结果如下
    ~/cgotest$ ~/go/bin/dlv core cgotest /mnt/wslg/dumps/core.main 
Type 'help' for list of commands.
(dlv) bt
 0  0x000000000046fde1 in runtime.raise
    at /usr/local/go/src/runtime/sys_linux_amd64.s:154
 1  0x000000000044b625 in runtime.dieFromSignal
    at /usr/local/go/src/runtime/signal_unix.go:942
 2  0x000000000044bc86 in runtime.sigfwdgo
    at /usr/local/go/src/runtime/signal_unix.go:1154
 3  0x000000000044a625 in runtime.sigtrampgo
    at /usr/local/go/src/runtime/signal_unix.go:432
 4  0x000000000046fde1 in runtime.raise
    at /usr/local/go/src/runtime/sys_linux_amd64.s:153
 5  0x000000000044b625 in runtime.dieFromSignal
    at /usr/local/go/src/runtime/signal_unix.go:942
 6  0x000000000044b1a6 in runtime.crash
    at /usr/local/go/src/runtime/signal_unix.go:1031
Sending output to pager...
 0  0x000000000046fde1 in runtime.raise
    at /usr/local/go/src/runtime/sys_linux_amd64.s:154
 1  0x000000000044b625 in runtime.dieFromSignal
    at /usr/local/go/src/runtime/signal_unix.go:942
 2  0x000000000044bc86 in runtime.sigfwdgo
    at /usr/local/go/src/runtime/signal_unix.go:1154
 3  0x000000000044a625 in runtime.sigtrampgo
    at /usr/local/go/src/runtime/signal_unix.go:432
 4  0x000000000046fde1 in runtime.raise
    at /usr/local/go/src/runtime/sys_linux_amd64.s:153
 5  0x000000000044b625 in runtime.dieFromSignal
    at /usr/local/go/src/runtime/signal_unix.go:942
 6  0x000000000044b1a6 in runtime.crash
    at /usr/local/go/src/runtime/signal_unix.go:1031
 7  0x000000000044b1a6 in runtime.sighandler
    at /usr/local/go/src/runtime/signal_unix.go:806
 8  0x000000000044a726 in runtime.sigtrampgo
    at /usr/local/go/src/runtime/signal_unix.go:490
 9  0x00000000004930b4 in ???
    at ?:-1
10  0x000000000049256b in C._cgo_a4c0d8419d5e_Cfunc_BufferSize
    at /tmp/go-build/buffer.cgo2.c:55
11  0x000000000046e284 in runtime.asmcgocall
    at /usr/local/go/src/runtime/asm_amd64.s:923
12  0x0000000000000000 in ???
    at ?:-1
13  0x0000000000462fb5 in runtime.cgocall
    at /usr/local/go/src/runtime/cgocall.go:185
14  0x0000000000475b87 in cgotest/cgotest/buffer._Cfunc_BufferSize
    at _cgo_gotypes.go:52
15  0x00000000004923fb in main.main.func1.BufferSize.3
    at ./buffer/buffer.go:22
16  0x0000000000492345 in cgotest/cgotest/buffer.BufferSize
    at ./buffer/buffer.go:22
17  0x0000000000492345 in main.main.func1
    at ./main.go:29
18  0x000000000046e601 in runtime.goexit
    at /usr/local/go/src/runtime/asm_amd64.s:1700

参考

  • dlv安装

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