(If you like articles title longer that the article itself, you’re on the right place.)

As the subject of the article, here’s a brief piece of code to define a library with a function whose name is also in libc. In the example we want to call the libc time() function inside our time() function.

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You can note the use of dlsym() function with the use of the flag RTDL_NEXT, that (from the man page) will find the next occurrence of a function in the search order after the current library. This allows one to provide a wrapper around a function in another shared library.

The code on my github.com.

Please note that you can find the gcc commands inside the branch, file compile.sh.