Question

Environment: linux x64, compiler gcc 4.x

Project has following structure:

static library "slib"
-- inside this library, there is static object "sobj"

dynamic library "dlib"
-- links statically "slib"

executable "exe":
-- links "slib" statically
-- links "dlib" dynamically

at end of the program, “sobj” is destructed twice. That behaviour is expected, BUT it is destructed twice at same memory address, i.e. same “this” in destructor – as the result there is double destruction problem.
I think it is due some symbol overlapping.

What the solution for that conflict? Maybe some linking option?

---

Here is test case:

---

main_exe.cpp

#include <cstdlib>

#include "static_lib.h"
#include "dynamic_lib.h"

int main(int argc, char *argv[])
{
    stat_useStatic();
    din_useStatic();
    return EXIT_SUCCESS;
}

---

static_lib.h

#ifndef STATIC_LIB_H
#define STATIC_LIB_H

#include <cstdio>

void stat_useStatic();
struct CTest
{
    CTest(): status(isAlive)
    {
        printf("CTest() this=%d\n",this);
    }
    ~CTest()
    {
        printf("~CTest() this=%d, %s\n",this,status==isAlive?"is Alive":"is Dead");
        status=isDead;
    }
    void use()
    {
        printf("use\n");
    }
    static const int isAlive=12385423;
    static const int isDead=6543421;
    int status;

    static CTest test;
};

#endif

---

static_lib.cpp

#include "static_lib.h"

CTest CTest::test;

void stat_useStatic()
{
    CTest::test.use();
}

---

dynamic_lib.h

#ifndef DYNAMIC_LIB_H
#define DYNAMIC_LIB_H

#include "static_lib.h"

#ifdef WIN32
#define DLLExport __declspec(dllexport)
#else
#define DLLExport 
#endif
DLLExport void din_useStatic();


#endif

---

dynamic_lib.cpp

#include "dynamic_lib.h"

DLLExport void din_useStatic()
{
    CTest::test.use();
}

---

CMakeLists.txt

project( StaticProblem )
cmake_minimum_required(VERSION 2.6)
if(WIN32)
else(WIN32)
    ADD_DEFINITIONS(-fPIC)
endif(WIN32)

ADD_LIBRARY( static_lib  STATIC static_lib.cpp static_lib.h)

ADD_LIBRARY( dynamic_lib SHARED dynamic_lib.cpp dynamic_lib.h)
TARGET_LINK_LIBRARIES( dynamic_lib static_lib )

ADD_EXECUTABLE( main_exe main_exe.cpp )
TARGET_LINK_LIBRARIES( main_exe static_lib dynamic_lib )

---

That example works OK, on windows, but on linux – there is problem.
As it works ok on windows, solution should be like change some linking option or something like that, but not change project structure or not use static vars.

Output:

Windows

CTest() this=268472624
CTest() this=4231488
use
use
~CTest() this=4231488, is Alive
~CTest() this=268472624, is Alive

Linux

CTest() this=6296204
CTest() this=6296204
use
use
~CTest() this=6296204, is Alive
~CTest() this=6296204, is Dead

Answer 1

OK, I have found solution:

http://gcc.gnu.org/wiki/Visibility

For example if change

static CTest test;

to

__attribute__ ((visibility ("hidden"))) static CTest test;

problem will gone.
Linux:

CTest() this=-1646158468
CTest() this=6296196
use
use
~CTest() this=6296196, is Alive
~CTest() this=-1646158468, is Alive

nm output before fix was:

0000000000200dd4 B _ZN5CTest4testE

after fix:

0000000000200d7c b _ZN5CTest4testE

Difference is changed global symbol “B” to local symbol “b”.

Instead of adding “attribute ((visibility (“hidden”)))” to symbols, it is possible to use compiler option “-fvisibility=hidden”. That option makes gcc to behave much more like Windows env.