CMake imported library behaviour

Question

I've a strange problem with CMake.

I'm importing Curl into my project, so I write for you a simplified summary of my CMakeLists.txt file.

ADD_LIBRARY (libcurl SHARED IMPORTED)

SET_PROPERTY(TARGET libcurl PROPERTY IMPORTED_LOCATION ../lib/libcurl.lib)

When I run CMake it generates the project files for MS VC++ (also for Linux). Then into the project file I find a wrong reference to curl library (libcurl-NOTFOUND)!

If I change my code into static import:

ADD_LIBRARY (libcurl STATIC IMPORTED)

SET_PROPERTY(TARGET libcurl PROPERTY IMPORTED_LOCATION ../lib/libcurl.lib)

I find the right reference to ../lib/libcurl.lib.

Do you have any idea why this happens?

Thank you very much!

Solution

For a shared library, the IMPORTED_LOCATION must point to the DLL, not the import lib. See the documentation. You might also want to set the IMPORTED_IMPLIB property.

BTW, CMake also has a find package for Curl; perhaps you could use that?

Comments

[User001]

Hello, Please let me know how the issue was resolved. I followed the below comment, but it is leading to much more errors.

[User001]

I have added the DLL to the IMPORTED_LOCATION.Also added the LIB with IMPORTED_IMPLIB But that is not resolving the error for the shared library linking.

[javs]

cmake will also need to see IMPORTED_IMPLIB if you claim your library is 'SHARED' in add_library. Common practice in Find*.cmake modules seems to be to declare it 'UNKNOWN' to avoid the issue.

[Kevin]

Also, the path provided to IMPORTED_LOCATION must be a full path, not a relative one.

[RAM]

It should be noted that cmake's doc on add_library has zero references to IMPORTED_IMPLIB.

[Angew is no longer proud of SO]

@RAM Zero references by full name. It does however tell you to look at all the IMPORTED_* properties for configuring the target, and just mentions the most important one (and it does say it must point to the main library file). Note that IMPORTED_IMPLIB is platform-specific, just like e.g. IMPORTED_SONAME. All the other IMPORTED_* properties may or may not be relevant, based on a given use case. It makes more sense for the docs to just point you to them all (as they do) instead of mentioning them all individually.

[RAM]

@AngewisnolongerproudofSO mentioning IMPORTED_* means nothing as represent about two dozen different vars, some of which are irrelevant. It also doesn't sound right to downplay support for Windows libraries as "platform-specific" because all libs are platform specific and Windows is one of the most popular target platforms, if not the most popular.