GCC 中__attribute__((constructor)和__attribute__(((destructor))的注意事项。

属性__attribute__((constructor)和__attribute__(((destructor))

1. __attribute__是可以修饰多个函数的，这给当然不例外。
2. 但是需要注意的是执行顺序，同一属性的函数执行顺序似乎不太好确定。原因的话等什么时候看看手册吧。
3. 如果是编译C++的话，我在WSL上用gcc(gcc version 9.3.0 (Ubuntu 9.3.0-17ubuntu1~20.04))编译发现无法运行，但是用Win10上装的(gcc version 4.9.2 (i686-posix-sjlj, built by strawberryperl.com project))又可以运行。至于是全局类的构造过程、析构过程、attribute((constructor)和__attribute__(((destructor))发生的顺序，无法确定。

#include <stdio.h>
__attribute__((constructor)) void before_main1()
{
    
    printf("before main1\n");
}

__attribute__((constructor)) void before_main2()
{
    
    printf("before main2\n");
}
__attribute__((destructor)) void after_main2()
{
    
    printf("after main2\n");
}
__attribute__((destructor)) void after_main1()
{
    
    printf("after main1\n");
}

int main()
{
    
    printf("in main\n");

    printf("before_main1: %p\n", before_main1);
    printf("before_main2: %p\n", before_main2);
    printf("after_main1: %p\n", after_main1);
    printf("after_main2: %p\n", after_main2);

    return 0;
}

gcc version 9.3.0 (Ubuntu 9.3.0-17ubuntu1~20.04)
before main1
before main2
in main
before_main1:   0x7fe4e40b4169
before_main2:   0x7fe4e40b4180
after_main1:    0x7fe4e40b41ae
after_main2:    0x7fe4e40b4197
after main1
after main2

TDM-GCC 4.9.2 64-bit Release/Debug
before main2
before main1
in main
before_main1:   0000000000401530
before_main2:   000000000040154B
after_main1:    0000000000401581
after_main2:    0000000000401566
after main2
after main1

gcc version 4.8.5 20150623 (Red Hat 4.8.5-44) (GCC)
before main1
before main2
in main
before_main1:   0x40057d
before_main2:   0x40058d
after_main1:    0x4005ad
after_main2:    0x40059d
after main1
after main2

#include<iostream>
using namespace std;

__attribute__((constructor)) void before_main1()
{
    
    cout<<"Before Main1"<<endl;
}
__attribute__((constructor)) void before_main2()
{
    
    cout<<"Before Main2"<<endl;
}
__attribute__((destructor)) void after_main1()
{
    
    cout<<"After Main1"<<endl;
}


class AAA{
    
    public:
    AAA(){
    
        cout<<"AAA construct"<<endl;
    }   
    ~AAA(){
    
        cout<<"AAA destructor" <<endl;
    }   
};
AAA A;
__attribute__((destructor)) void after_main2()
{
    
    cout<<"After Main2"<<endl;
}

int main()
{
    
    cout<<"in main"<<endl;
    return 0;
}

* .\a.exe
AAA construct
Before Main2
Before Main1
in main
After Main1
After Main2
AAA destructor

#include<iostream>
using namespace std;

__attribute__((constructor)) void before_main1()
{
    
    cout<<"Before Main1"<<endl;
}
__attribute__((constructor)) void before_main2()
{
    
    cout<<"Before Main2"<<endl;
}
__attribute__((destructor)) void after_main1()
{
    
    cout<<"After Main1"<<endl;
}
__attribute__((destructor)) void after_main2()
{
    
    cout<<"After Main2"<<endl;
}


class AAA{
    
    public:
    AAA(){
    
        cout<<"AAA construct"<<endl;
    }   
    ~AAA(){
    
        cout<<"AAA destructor" <<endl;
    }   
};
AAA A;

int main()
{
    
    cout<<"in main"<<endl;
    return 0;
}
gcc version 4.9.2 (i686-posix-sjlj, built by strawberryperl.com project)
* .\a.exe
AAA construct
Before Main2
Before Main1
in main
After Main1
After Main2
AAA destructor


gcc version 4.8.5 20150623 (Red Hat 4.8.5-44) (GCC)
Segmentation fault