C++ 未找到 -lboost_system 的库
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library not found for -lboost_system
提问by jim
I installed boost using macports. The files appear to be in /opt/local/include/boost/
我使用 macports 安装了 boost。这些文件似乎在 /opt/local/include/boost/
My makefile is no longer working and I get the following error
我的 makefile 不再工作，并且出现以下错误
Undefined symbols:
"boost::system::generic_category()", referenced from:
__static_initialization_and_destruction_0(int, int)in client.o
__static_initialization_and_destruction_0(int, int)in client.o
"boost::system::system_category()", referenced from:
boost::asio::error::get_system_category() in client.o
boost::system::error_code::error_code()in client.o
__static_initialization_and_destruction_0(int, int)in client.o
ld: symbol(s) not found
collect2: ld returned 1 exit status
make: *** [client] Error 1
at school the solution was to use -lboost_system as an argument to g++, but now that I've taken the project home to my mac, this does not work. I think this is mostly due to the fact that at school the boost files were at usr/local/lib (or somewhere similar).
在学校，解决方案是使用 -lboost_system 作为 g++ 的参数，但现在我已将该项目带回家我的 mac，这不起作用。我认为这主要是因为在学校时 boost 文件位于 usr/local/lib （或类似的地方）。
When I add the -lboost_system argument i get the following message
当我添加 -lboost_system 参数时，我收到以下消息
g++ -I/opt/local/include -lboost_system -o client client.o Packet.o
ld: library not found for -lboost_system
collect2: ld returned 1 exit status
make: *** [client] Error 1
I've tried a few variations using -L and -l, but I can't seem to find a combo that works. At school I also do not have to use -L. I've read a few other posts here about similar problems, but they fixed it by adding -l flags which arent working for me.
我已经使用 -L 和 -l 尝试了一些变体，但我似乎找不到有效的组合。在学校我也不必使用-L。我在这里阅读了一些关于类似问题的其他帖子，但他们通过添加对我不起作用的 -l 标志来修复它。
Help! thanks!
帮助！谢谢！
回答by mu is too short
You're missing a -L/opt/local/lib. You should be able to set the LDFLAGSin your Makefile:
你缺少一个-L/opt/local/lib. 你应该能够LDFLAGS在你的 Makefile 中设置：
LDFLAGS=-L/opt/local/lib
This assumes that the Boost libraries are in /opt/local/libof course.
这假设 Boost 库在/opt/local/lib当然。
If you're not using the usual CXXFLAGSand LDFLAGSvariables in your Makefile, then add the -L/opt/local/libdirectly in your final rule:
如果你没有在你的 Makefile 中使用普通CXXFLAGS和LDFLAGS变量，那么-L/opt/local/lib直接在你的最终规则中添加：
client: client.o Packet.o
g++ -L/opt/local/lib -o client client.o Packet.o -lboost_system
The -Ionly tells the compiler where header files are, the linker needs libraries and you use -Lfor that.
该-I只告诉编译器在哪里头文件，链接器需要磁带库，并且使用-L了点。
回答by serup
You could try to look for it in your system like this :
您可以尝试在您的系统中查找它，如下所示：
/sbin/ldconfig -p | grep boost_system | cut -d\> -f2
if the library is installed, then it should show something like this:
如果安装了库，那么它应该显示如下内容：
/usr/lib/x86_64-linux-gnu/libboost_system.so.1.58.0
or it will show just a blank line
否则它只会显示一个空行
In your case it seems that boost is installed in another place, hence the need for additional linker information, hence the need for the -L switch, if however you have it in /usr/lib, as I have then no need for additional info in makefile
在你的情况下，boost 似乎安装在另一个地方，因此需要额外的链接器信息，因此需要 -L 开关，如果你在 /usr/lib 中有它，那么我不需要额外的信息在生成文件中
