静态与动态链接

Question

I'm trying to understand how the ELF looks like for a statically vs. a dynamically linked program.

I understand that this is how static linking works:

In my case, I have two files, foo.c and bar.c . I also have their object files; foo.o and bar.o . With the objdump command, I can see the relocations in each file.

How do I statically link the foo.o and bar.o ?

How do I dynamically link the foo.o and bar.o ?

How can I see the difference in the output files?

Answer 1

Linking dynamically is the default mode of most linkers these days. If you want to link statically you have to use the -static flag when linking. To clarify, when I say "linking dynamically" versus "linking statically" I mean the linking with external libraries, and not generating a library that in turn can be linked (dynamically or statically).

The difference can't be seen in the object files you pass to the linker, as it has nothing to do with the compiler and object-file generation, the result can only be seen in the resulting executable program after linking, and the biggest difference is that the executable will most likely be larger.

The resulting and fully linked executable will be larger because then all the libraries (for which there are static libraries) will actually be linked into the executable program quite literally. It's basically including the libraries object files together with your own object files. Actually, on POSIX platforms static libraries are just archives of object files.