C++ 对“dlsym”的未定义引用
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Undefined reference to 'dlsym'
提问by evinje
I have seen a lot of similar posts, but tried every trick in the book and am still struggling. Everything was working fine, but after installing/removing wireshark with some components/disselectors it all got messed up. I don't remember exactly which libraries/packages got uninstalled, but probably a lot more than I noticed.
我看过很多类似的帖子，但是尝试了书中的所有技巧，仍然在挣扎。一切正常，但是在安装/删除带有一些组件/选择器的wireshark之后，一切都搞砸了。我不记得到底卸载了哪些库/包，但可能比我注意到的要多得多。
If I create a simple main.cpp file like this one:
如果我创建一个像这样的简单 main.cpp 文件：
#include <SQLAPI.h>
int main()
{
SAConnection con;
return 0;
}
and try
并尝试
g++ main.cpp -lsqlapi -ldl
g++ main.cpp -lsqlapi -ldl
it gives me the following error messages:
它给了我以下错误消息：
/usr/local/lib/libsqlapi.so: undefined reference to `dlsym'
/usr/local/lib/libsqlapi.so: undefined reference to `dlerror'
/usr/local/lib/libsqlapi.so: undefined reference to `dlopen'
/usr/local/lib/libsqlapi.so: undefined reference to `dlclose'
collect2: error: ld returned 1 exit status
I have tried to put -ldl before -lsqlapi as some have suggested that the order is important. If I use gcc instead of g++ the error is:
我试图将 -ldl 放在 -lsqlapi 之前，因为有些人认为顺序很重要。如果我使用 gcc 而不是 g++ 错误是：
/usr/bin/ld: /tmp/ccwBI4tj.o: undefined reference to symbol '__gxx_personality_v0@@CXXABI_1.3'
/usr/lib/x86_64-linux-gnu/libstdc++.so.6: error adding symbols: DSO missing from command line
collect2: error: ld returned 1 exit status
I am able to compile and run the file if SAConnection is removed.
如果删除了 SAConnection，我就可以编译和运行该文件。
I don't think it has anything to do with SQLAPI, because I experience similar problems with libboost. I don't have a small code example, but when I compile a project that was successfully compiled last week, I get the error:
我认为它与 SQLAPI 没有任何关系，因为我在使用 libboost 时遇到了类似的问题。我没有小代码示例，但是当我编译上周成功编译的项目时，出现错误：
/usr/bin/ld: debug/components/helloworld/HelloWorld.o: undefined reference to symbol '_ZN5boost6system15system_categoryEv'
/usr/lib/x86_64-linux-gnu/libboost_system.so.1.53.0: error adding symbols: DSO missing from command line
collect2: error: ld returned 1 exit status
This project is using a Makefile that has been unchanged, so it has to be something on my system that is not correct. I have tried to reinstall build-essential.
该项目使用的是未更改的 Makefile，因此它必须是我系统上不正确的内容。我试图重新安装 build-essential。
Using Ubuntu 64 bit 13.10 with g++ version 4.8.1.
使用 Ubuntu 64 位 13.10 和 g++ 版本 4.8.1。
回答by evinje
I have found the solution; setting the -Wl,--no-as-needed before -ldl The new compile command is
我找到了解决办法；在 -ldl 之前设置 -Wl,--no-as-needed 新的编译命令是
gcc main.cpp -lsqlapi -lstdc++ -Wl,--no-as-needed -ldl
gcc main.cpp -lsqlapi -lstdc++ -Wl,--no-as-needed -ldl
Apparently it has something to do with recent versions of gcc/ld default to linking with --as-needed.
显然它与最近版本的 gcc/ld 默认链接 --as-needed 有关系。
