CMake can't find external library

Question

I am trying to build an application that uses the LibUSB library.

In a previous question I asked here I was told to use find_path and find_library to make CMake search for the headers and binaries. However even after manually looking up the library's installation locations with dnf and specifying them as PATHS or HINTS I always still get the error:

/usr/bin/ld: cannot find -lUSB
collect2: error: ld returned 1 exit status

Below is the relevent cmakelists.txt, my import line in main.cpp is #include <libusb-1.0/libusb.h>

add_executable(project main.cpp)
find_path(LIBUSB_INCLUDE_DIR
  NAMES libusb.h
  PATHS "/usr/include/"
  PATH_SUFFIXES "include" "libusb")
find_library(LIBUSB_LIBRARY
  NAMES USB
  HINTS "/usr/lib/" "/usr/lib64/" "/usr/include/"
  PATH_SUFFIXES "lib" "lib32" "lib64")

target_include_directories(project PRIVATE "/usr/lib/" "/usr/lib64/")
target_link_libraries(project USB)

Clearly I'm doing something wrong in this kludge of hacks, but could someone tell me what?

If you did not understand my answer, please help improve it by comments to the answer. — usr1234567, Jan 26 '16 at 17:09
@usr1234567 I understood your answer but thought I was now asking a different question — Segfault, Jan 27 '16 at 08:23

score 1 · Answer 1 · answered Jan 26 '16 at 16:05

1

You're not using the result of your find operations anywhere. You tell CMake to find the headers and store the found paths in LIBUSB_INCLUDE_DIR, and to find the library and store its location in LIBUSB_LIBRARY, and then you go to ignore these and use hardcoded "/usr/lib/" "/usr/lib64/" and USB instead. Try this:

target_include_directories(project PRIVATE ${LIBUSB_INCLUDE_DIR})
target_link_libraries(project ${LIBUSB_LIBRARY})

answered Jan 26 '16 at 16:05

Angew is no longer proud of SO

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I tried your solution, however my error changed to: `/usr/bin/ld: CMakeFiles/botspotptp.dir/main.cpp.o: undefined reference to symbol 'libusb_set_debug' /usr/lib64/libusb-1.0.so.0: error adding symbols: DSO missing from command line collect2: error: ld returned 1 exit status` What is a DSO? – Segfault Jan 27 '16 at 08:40
@LordNibbler Have you asked uncle Google? Perhaps you should review a few tutorials on linking "manually," before CMake enters the picture. – Angew is no longer proud of SO Jan 27 '16 at 09:10
I don't see what manually linking has to do with CMake; besides as any good internet citizen I thoroughly scoured google before posting here. I found a reference to needing pthread, which I found and included using the same method, but that did not resolve or change the issue. – Segfault Jan 27 '16 at 10:34
@LordNibbler I suggested that because a "DSO" (dynamic shared object, IIUC) has nothing to do with CMake. And because you were talking about include directories and headers in the context of unresolved references. – Angew is no longer proud of SO Jan 27 '16 at 10:48

score 0 · Accepted Answer · edited May 23 '17 at 11:59

0

As shown Back in the original question, here, all of the finding and including functions can be replaced simply with:

target_link_libraries(project_name <other_dependencies> usb-1.0),

in the file where the build target is defined.

edited May 23 '17 at 11:59

Community

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answered Jan 29 '16 at 08:40

Segfault

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CMake can't find external library

2 Answers2