Linux上的C ++，确认库中的代码未静态链接到生成的可执行文件中

Question

C++ on Linux, I'm building an executable which previously linked against a static library (.a), I've updated the build so that it now links against this library dynamically (.so). I want to confirm that the code from this library is no longer statically being linked into the executable. I was hoping to be able to confirm this by comparing the nm output from the statically linked vs dynamically linked executable but there are so many differences between these that it would be a manual effort to confirm this way...wondering if there is a better way that anyone can recommend?

Answer 1

There's the nm command. It lists the modules functions. Runs the nm command and grep a function you know is in the lib/so. If it's dynamically linked (so library) you'll see a "U" attribute to it.

Example (perl path is made up):

nm /bin/perl | grep fprintf

Output:

U fprintf@@GLIBC_2.2.5

Note: ldd is useful for knowing if you depend on an SO. But this SO can be a dependency of another SO. In some cases you could get both static and dynamic versions of the library linked to your binary causing horrible memory issues (usually seen as double free error).