My executable has references to dlcose - but wherefor?

Asked Aug 08 '22 at 21:10

Active Aug 08 '22 at 21:33

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I'm trying to link some executable, built from C++ source files, and getting:

/usr/bin/ld: examples/CMakeFiles/whatever/main.cpp.o: undefined reference to symbol 'dlclose@@GLIBC_2.2.5'

Now, I know how to "fix" this:

How to fix undefined reference to symbol 'dlclose@@GLIBC_2.2.5' from glad.c

but - I don't understand where this dependency is coming from. I'm not dlopen'ing nor dlclose'ing anything that I know of, nor can I think of one of my dependency libraries which does so (although I can't be sure).

How do I investigate the origin of this requirement, to figure out "who's to blame" for the need for libdl?

Notes:

I have control of the build process via CMake.
I have access to the source files (but not the source file of dependency libraries - just their headers).

edited Aug 08 '22 at 21:33

asked Aug 08 '22 at 21:10

einpoklum

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Use `ldd` on dependencies until you find `libdl` in the output? – Stephen Newell Aug 08 '22 at 21:13
@StephenNewell: ldd is for executables, not for `.o` or `.a` files... or am I wrong? **Edit:** It seems I am wrong. `.so` files seem to be usable with ldd. – einpoklum Aug 08 '22 at 21:14
Good point, I assumed you were linking against `so`s. `grep` for `dlclose`. – Stephen Newell Aug 08 '22 at 21:16
Your build output says `main.cpp.o`, so I assume you already checked `main.cpp` without success. – Stephen Newell Aug 08 '22 at 21:16
@StephenNewell: When I grep one my `main.cpp.o` I get "binary file matches"... I could use objdump or nm, but that won't tell me where the symbol is used. – einpoklum Aug 08 '22 at 21:17
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Do you have access to the source file? You could run the pre-processor in case the call is in an inlined function. – Stephen Newell Aug 08 '22 at 21:22
`objdump -D ... | less` and `/dlclose` should give the location. – KamilCuk Aug 08 '22 at 21:23
@KamilCuk: That didn't do the trick. Tried it also with c++filt before the less, no help either. – einpoklum Aug 09 '22 at 10:40

My executable has references to dlcose - but wherefor?

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