二进制中的变量disapears在静态库中可用

本文介绍了二进制中的变量disapears在静态库中可用的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！

问题描述

我有提到的问题。我在静态库中创建一个对象，当我在静态库中运行 nm 时，但是当我将lib链接到一个二进制文件并运行 nm 它已经消失。我知道这个问题以前被问过，但我找不到任何答案。对我来说重要的是能够在二进制中保留该变量，因为我们试图对二进制中的静态库执行版本检查。请帮忙。谢谢。示例代码如下：

test.h

  #ifndef TEST_H 
 #define TEST_H 
 
 class Test 
 {
 public：
 Test（）; 
}; 
 
 extern Test * gpTest; 
 
 #endif

test.cpp

  #includetest.h ）
 {
 gpTest = this; 
} 
 
测试测试;

main.cpp

  #includetest.h
 #include< iostream> 
 
 using namespace std; 
 
 Test * gpTest = NULL; 
 
 int main（）
 {
 return 0; 
}

BUILD

  g ++ -c test.cpp -o test.o 
 ar cr test.a test.o 
 g ++ main.cpp -o app -L / home / duminda / intest / test.a

test.a

  0000000000000054 t全局构造函数键入_ZN4TestC2Ev 
 000000000000002b t __static_initialization_and_destruction_0 int，int）
 0000000000000016 T Test :: Test（）
 0000000000000000 T Test :: Test（）
 U __gxx_personality_v0 
 U gpTest 
 0000000000000000 B test

nm -C app
$ b <$ c $ p> 0000000000600e10 d _DYNAMIC 0000000000600fe8 d _GLOBAL_OFFSET_TABLE_ 0000000000400754 t全局构造函数键入gpTest 0000000000400858 R _IO_stdin_used w _Jv_RegisterClasses 0000000000400717 t __static_initialization_and_destruction_0（int，int） U std :: ios_base :: Init :: Init（）@@ GLIBCXX_3.4 U std :: ios_base :: Init ::〜 Init（）@@ GLIBCXX_3.4 0000000000601050 b std :: __ ioinit 0000000000600df0 d __CTOR_END__ 0000000000600de0 d __CTOR_LIST__ 0000000000600e00 D __DTOR_END__ 0000000000600df8 d __DTOR_LIST__ 0000000000400968 r __FRAME_END__ 0000000000600e08 d __JCR_END__ 0000000000600e08 d __JCR_LIST__ 0000000000601038 A __bss_start U __cxa_atexit @@ GLIBC_2.2.5 0000000000601028 D __data_start 0000000000400810 t __do_global_ctors_aux 0000000000400670 t __do_global_dtors_aux 0000000000601030 D __dso_handle w __gmon_start__ U __gxx_personality_v0 @@ CXXABI_1.3 0000000000600ddc d __init_array_end 0000000000600ddc d __init_array_start 0000000000400770 T __libc_csu_fini 0000000000400780 T __libc_csu_init U __libc_start_main @@ GLIBC_2.2.5 0000000000601038 A _edata 0000000000601058 A _end 0000000000400848 T _fini 00000000004005a0 T _init 0000000000400620 T _start 000000000040064c t call_gmon_start 0000000000601038 b completed.6096 0000000000601028 W data_start 0000000000601040 b dtor_idx.6098 00000000004006e0 t frame_dummy 0000000000601048 B gpTest 000000000040070c T main

解决方案

寻找：D。看起来链接器标志 - 整个归档是确保所有符号在静态库，无论是否由应用程序访问或不进入应用程序。虽然我仍然无法让这个工作，我想我在正确的道路。

I have the problem mentioned. I create an object inside a static lib, it is there when I run nm on the static lib, but when i link the lib to a binary and run nm it has disappeared. I know this problem has been asked before, but I could not find any answers. It is important for me to be able to retain that variable in the binary because we are trying to implement version checks for static libs in a binary. Please help. Thank you. Example code follows:
test.h
#ifndef TEST_H #define TEST_H class Test { public: Test(); }; extern Test* gpTest; #endif
test.cpp
#include "test.h" Test::Test() { gpTest = this; } Test test;
main.cpp
#include "test.h" #include <iostream> using namespace std; Test* gpTest = NULL; int main() { return 0; }
BUILD
g++ -c test.cpp -o test.o ar cr test.a test.o g++ main.cpp -o app -L/home/duminda/intest/test.a
nm -C test.a
0000000000000054 t global constructors keyed to _ZN4TestC2Ev 000000000000002b t __static_initialization_and_destruction_0(int, int) 0000000000000016 T Test::Test() 0000000000000000 T Test::Test() U __gxx_personality_v0 U gpTest 0000000000000000 B test
nm -C app
0000000000600e10 d _DYNAMIC 0000000000600fe8 d _GLOBAL_OFFSET_TABLE_ 0000000000400754 t global constructors keyed to gpTest 0000000000400858 R _IO_stdin_used w _Jv_RegisterClasses 0000000000400717 t __static_initialization_and_destruction_0(int, int) U std::ios_base::Init::Init()@@GLIBCXX_3.4 U std::ios_base::Init::~Init()@@GLIBCXX_3.4 0000000000601050 b std::__ioinit 0000000000600df0 d __CTOR_END__ 0000000000600de0 d __CTOR_LIST__ 0000000000600e00 D __DTOR_END__ 0000000000600df8 d __DTOR_LIST__ 0000000000400968 r __FRAME_END__ 0000000000600e08 d __JCR_END__ 0000000000600e08 d __JCR_LIST__ 0000000000601038 A __bss_start U __cxa_atexit@@GLIBC_2.2.5 0000000000601028 D __data_start 0000000000400810 t __do_global_ctors_aux 0000000000400670 t __do_global_dtors_aux 0000000000601030 D __dso_handle w __gmon_start__ U __gxx_personality_v0@@CXXABI_1.3 0000000000600ddc d __init_array_end 0000000000600ddc d __init_array_start 0000000000400770 T __libc_csu_fini 0000000000400780 T __libc_csu_init U __libc_start_main@@GLIBC_2.2.5 0000000000601038 A _edata 0000000000601058 A _end 0000000000400848 T _fini 00000000004005a0 T _init 0000000000400620 T _start 000000000040064c t call_gmon_start 0000000000601038 b completed.6096 0000000000601028 W data_start 0000000000601040 b dtor_idx.6098 00000000004006e0 t frame_dummy 0000000000601048 B gpTest 000000000040070c T main
解决方案
I found what I was looking for :D. It seems that linker flag --whole-archive is there to make sure all symbols in static lib regardless of whether they are accessed by app or not get into app. Though I still have trouble getting this to work, I guess I am on the right path.

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