In-depth analysis of centos' dynamic link library joint compilation technology

What is a dynamic link library

On Windows it is dynamic linklibrary (DLL), suffix? xxx.dll

It is Shared Library on UNIX or Linux. The suffix is ​​xxx.so

Compile the file into a dynamic link library in .so format

gcc -o libme.so wso.c -shared

Compile wso.c into libme.so and the library name is me

lib so is the prefix and suffix

Joint compilation

gcc -L /root/myc/ -l me ws.c -o newws

-L Folder location of dynamic link library

-l The library name of the dynamic link library (remove the first lib and .so is the library name)

Next you will find that the compilation is successful, but the operation still fails

The reason for failure is that the operating system cannot find it

In fact, Linux, like Windows, has a system library folder similar to system32. Various public class libraries are placed here

CentOS has two folders that store public libraries that are very similar to windows

/lib kernel level

/usr/lib User system level

/usr/lib64/ Only available on 64-bit systems

You have to make a good library, it doesn’t matter if you put it in a random way

Solution

Copy the SO file we made to the public library (cp command)

Then execute ldconfig (the dynamic library is cached. If new things are added, the cache needs to be updated again)

Run newws successfully

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