Cmake is unable to find packages of Gmock

Question

I am new to Cmake and Gtest. I have a problem with in CMake

find_package(GMock REQUIRED)

and

target_link_libraries(runtest ${GMOCK_BOTH_LIBRARIES} pthread).

When I build the project, CMake is unable find the GMock packages.

But when I mentioned the absolute paths of library, it is working fine.

For example:

set(GMOCK_INCLUDE_DIRS /usr/local/include/gmock)

set(GMOCK_BOTH_LIBRARIES /usr/local/lib/libgmock.a /usr/local/lib/libgmock_main.a /usr/local/lib/libgtest.a /usr/local/lib/libgtest_main.a)

Now the problem is my Supervisor recommended me to find the solution to run the code using find packages only. After doing some research, I came to know that FindGMock.cmake file is missing from the Cmake modules. I added it and run code again with find_package(), but still it is not working.

Errors are undefined references to functionalities of Gmock and Gtest.

For instance :

undefined reference to `testing::Message::Message()'.

undefined reference to testing::internal::GetBoolAssertionFailureMessage.
undefined reference totesting::internal::AssertHelper::~AssertHelper()'

Like this there too many errors.

Could anyone please explain me, how to make CMake to find the GMock packages automatically?

Answer 1

Here's a step-by-step example of building and linking to GMock from a CMake project on Linux from scratch. Steps 0-4 cover building and installing GMock while steps 5 and beyond address the question.

These steps are fairly generic and will work with little modification for any project that provides its own CMake package.

Step 0: Create a working directory

From my home folder, I created a blank directory called test:

alex:~$ mkdir test
alex:~$ cd test
alex:~/test$ ls

Step 1: Download GMock

GMock is included in the Google Test repository, so we clone that repository.

alex:~/test$ git clone https://github.com/google/googletest
Cloning into 'googletest'...
remote: Enumerating objects: 24427, done.
remote: Counting objects: 100% (92/92), done.
remote: Compressing objects: 100% (45/45), done.
remote: Total 24427 (delta 44), reused 72 (delta 38), pack-reused 24335
Receiving objects: 100% (24427/24427), 10.32 MiB | 2.68 MiB/s, done.
Resolving deltas: 100% (18062/18062), done.

Step 2: Configure GMock

We'll use the following command to build the googletest repository; GMock is included by default.

$ cmake -S googletest/ -B _build/googletest -DCMAKE_BUILD_TYPE=RelWithDebInfo

The -S flag sets the source directory to the root of the Google Test repository we just cloned. This tells CMake which project it's building. The -B flag sets the binary directory to ~/test/_build/googletest, which is where CMake will store intermediate build outputs before they are installed. This should always be distinct from the source directory. Finally, since we are using a single-configuration generator (Make is the default on Linux), we must specify the build type at this time. I have chosen RelWithDebInfo to keep debugging easy, but also to enable optimizations.

In general, you should always build your project with in the same configuration as its dependencies, so we'll use RelWithDebInfo again later.

For more detail on how to configure generic CMake projects, I'll refer you to this question/answer: How do I build a CMake project?

Finally, here's the output of running the command:

alex:~/test$ cmake -S googletest/ -B _build/googletest -DCMAKE_BUILD_TYPE=RelWithDebInfo
-- The C compiler identification is GNU 9.4.0
-- The CXX compiler identification is GNU 9.4.0
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Check for working C compiler: /usr/bin/cc - skipped
-- Detecting C compile features
-- Detecting C compile features - done
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Check for working CXX compiler: /usr/bin/c++ - skipped
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Found Python: /usr/bin/python3.10 (found version "3.10.4") found components: Interpreter
-- Looking for pthread.h
-- Looking for pthread.h - found
-- Performing Test CMAKE_HAVE_LIBC_PTHREAD
-- Performing Test CMAKE_HAVE_LIBC_PTHREAD - Failed
-- Looking for pthread_create in pthreads
-- Looking for pthread_create in pthreads - not found
-- Looking for pthread_create in pthread
-- Looking for pthread_create in pthread - found
-- Found Threads: TRUE
-- Configuring done
-- Generating done
-- Build files have been written to: /home/alex/test/_build/googletest

Step 3: Build GMock

Now we'll go ahead and run the build. The following command will work with any single-config generator:

alex:~/test$ cmake --build _build/googletest/
[ 12%] Building CXX object googletest/CMakeFiles/gtest.dir/src/gtest-all.cc.o
[ 25%] Linking CXX static library ../lib/libgtest.a
[ 25%] Built target gtest
[ 37%] Building CXX object googlemock/CMakeFiles/gmock.dir/src/gmock-all.cc.o
[ 50%] Linking CXX static library ../lib/libgmock.a
[ 50%] Built target gmock
[ 62%] Building CXX object googlemock/CMakeFiles/gmock_main.dir/src/gmock_main.cc.o
[ 75%] Linking CXX static library ../lib/libgmock_main.a
[ 75%] Built target gmock_main
[ 87%] Building CXX object googletest/CMakeFiles/gtest_main.dir/src/gtest_main.cc.o
[100%] Linking CXX static library ../lib/libgtest_main.a
[100%] Built target gtest_main

The build should complete relatively quickly.

Step 4: Installing GMock

At this point, you could run sudo cmake --install _build/googletest/ to install it globally to /usr/local, but I wouldn't recommend this. It's much better to keep a frequently updated dependency like Google Test/GMock tied to the project that's using it.

Instead, we will install it to a project-local prefix, like so:

alex:~/test$ cmake --install _build/googletest/ --prefix _local
-- Install configuration: "RelWithDebInfo"
-- Installing: /home/alex/test/_local/include
-- Installing: /home/alex/test/_local/include/gmock
-- Installing: /home/alex/test/_local/include/gmock/gmock-matchers.h
-- Installing: /home/alex/test/_local/include/gmock/gmock-function-mocker.h
-- Installing: /home/alex/test/_local/include/gmock/internal
-- Installing: /home/alex/test/_local/include/gmock/internal/gmock-pp.h
-- Installing: /home/alex/test/_local/include/gmock/internal/gmock-internal-utils.h
-- Installing: /home/alex/test/_local/include/gmock/internal/gmock-port.h
-- Installing: /home/alex/test/_local/include/gmock/internal/custom
-- Installing: /home/alex/test/_local/include/gmock/internal/custom/gmock-port.h
-- Installing: /home/alex/test/_local/include/gmock/internal/custom/gmock-matchers.h
-- Installing: /home/alex/test/_local/include/gmock/internal/custom/gmock-generated-actions.h
-- Installing: /home/alex/test/_local/include/gmock/internal/custom/README.md
-- Installing: /home/alex/test/_local/include/gmock/gmock-more-actions.h
-- Installing: /home/alex/test/_local/include/gmock/gmock-more-matchers.h
-- Installing: /home/alex/test/_local/include/gmock/gmock-nice-strict.h
-- Installing: /home/alex/test/_local/include/gmock/gmock.h
-- Installing: /home/alex/test/_local/include/gmock/gmock-cardinalities.h
-- Installing: /home/alex/test/_local/include/gmock/gmock-spec-builders.h
-- Installing: /home/alex/test/_local/include/gmock/gmock-actions.h
-- Installing: /home/alex/test/_local/lib/libgmock.a
-- Installing: /home/alex/test/_local/lib/libgmock_main.a
-- Installing: /home/alex/test/_local/lib/pkgconfig/gmock.pc
-- Installing: /home/alex/test/_local/lib/pkgconfig/gmock_main.pc
-- Installing: /home/alex/test/_local/lib/cmake/GTest/GTestTargets.cmake
-- Installing: /home/alex/test/_local/lib/cmake/GTest/GTestTargets-relwithdebinfo.cmake
-- Installing: /home/alex/test/_local/lib/cmake/GTest/GTestConfigVersion.cmake
-- Installing: /home/alex/test/_local/lib/cmake/GTest/GTestConfig.cmake
-- Up-to-date: /home/alex/test/_local/include
-- Installing: /home/alex/test/_local/include/gtest
-- Installing: /home/alex/test/_local/include/gtest/gtest-param-test.h
-- Installing: /home/alex/test/_local/include/gtest/internal
-- Installing: /home/alex/test/_local/include/gtest/internal/gtest-port-arch.h
-- Installing: /home/alex/test/_local/include/gtest/internal/gtest-string.h
-- Installing: /home/alex/test/_local/include/gtest/internal/gtest-death-test-internal.h
-- Installing: /home/alex/test/_local/include/gtest/internal/gtest-type-util.h
-- Installing: /home/alex/test/_local/include/gtest/internal/gtest-port.h
-- Installing: /home/alex/test/_local/include/gtest/internal/gtest-internal.h
-- Installing: /home/alex/test/_local/include/gtest/internal/gtest-param-util.h
-- Installing: /home/alex/test/_local/include/gtest/internal/gtest-filepath.h
-- Installing: /home/alex/test/_local/include/gtest/internal/custom
-- Installing: /home/alex/test/_local/include/gtest/internal/custom/README.md
-- Installing: /home/alex/test/_local/include/gtest/internal/custom/gtest.h
-- Installing: /home/alex/test/_local/include/gtest/internal/custom/gtest-port.h
-- Installing: /home/alex/test/_local/include/gtest/internal/custom/gtest-printers.h
-- Installing: /home/alex/test/_local/include/gtest/gtest-matchers.h
-- Installing: /home/alex/test/_local/include/gtest/gtest-death-test.h
-- Installing: /home/alex/test/_local/include/gtest/gtest-spi.h
-- Installing: /home/alex/test/_local/include/gtest/gtest.h
-- Installing: /home/alex/test/_local/include/gtest/gtest-test-part.h
-- Installing: /home/alex/test/_local/include/gtest/gtest-typed-test.h
-- Installing: /home/alex/test/_local/include/gtest/gtest_prod.h
-- Installing: /home/alex/test/_local/include/gtest/gtest-assertion-result.h
-- Installing: /home/alex/test/_local/include/gtest/gtest_pred_impl.h
-- Installing: /home/alex/test/_local/include/gtest/gtest-message.h
-- Installing: /home/alex/test/_local/include/gtest/gtest-printers.h
-- Installing: /home/alex/test/_local/lib/libgtest.a
-- Installing: /home/alex/test/_local/lib/libgtest_main.a
-- Installing: /home/alex/test/_local/lib/pkgconfig/gtest.pc
-- Installing: /home/alex/test/_local/lib/pkgconfig/gtest_main.pc

The --prefix flag tells cmake --install into which directory to install the project. Here, we've chosen a directory named _local in our working directory. The name of this folder is arbitrary. I've chosen this name to mirror the /usr/local prefix naming and to play nicely with a common .gitignore strategy of ignoring top-level directories prefixed with and underscore.

Notice in the command output what's getting installed. Headers, the GTest and GMock static libraries, yes, but also pkg-config files and, most importantly, the CMake package files:

-- Installing: /home/alex/test/_local/lib/cmake/GTest/GTestTargets.cmake
-- Installing: /home/alex/test/_local/lib/cmake/GTest/GTestTargets-relwithdebinfo.cmake
-- Installing: /home/alex/test/_local/lib/cmake/GTest/GTestConfigVersion.cmake
-- Installing: /home/alex/test/_local/lib/cmake/GTest/GTestConfig.cmake

These are the files that find_package will use (soon) to load GTest into a dependent project. The two standard files are GTestConfig.cmake and GTestConfigVersion.cmake. The first one is the most important, and it's responsible for actually implementing the CMake package. It will ultimately load GTestTargets.cmake and GTestTargets-relwithdebinfo.cmake, which are specific to GTest. Notice also how RelWithDebInfo appears again in the generated file name; that's because config-specific information is stored there. If you want to support multiple configs, you'll need to redo steps 2-4 with a new CMAKE_BUILD_TYPE (e.g. Debug, Release, MinSizeRel)

Step 5: Creating an example project

Let's create a simple example project now that uses GMock. First, we'll create a directory for it:

alex:~/test$ mkdir example

and now we'll go in and create some files:

alex:~/test$ cd example/
alex:~/test/example$ touch CMakeLists.txt main.cpp

Using your favorite text editor, add the following contents to main.cpp:

#include <gmock/gmock.h>

using namespace testing;

struct Example : public Test {};

TEST_F(Example, AlwaysPass) { ASSERT_THAT(0, Eq(0)); }
TEST_F(Example, AlwaysFail) { ASSERT_THAT(0, Eq(1)); }

This is as basic of a "hello world" for GMock as I could come up with. It has one test that always passes and another that always fails (just so we can see the various outputs).

Now we'll write the build script in CMakeLists.txt:

cmake_minimum_required(VERSION 3.23)
project(example)

find_package(GTest REQUIRED)

add_executable(example main.cpp)
target_link_libraries(example PRIVATE GTest::gmock_main)

Once again, this is as simple as can be.

The first two lines are required boilerplate. They must always¹ appear as the first two lines of your project, in that order, with nothing before or in between.

The first command, cmake_minimum_required, tells CMake which set of backwards-compatibility policies to enable. It does not put CMake into an emulation mode or anything like that. You must test your build with the version written there because CMake will not stop you from using features that are too new for the declared minimum version.

The second command, project, names your project and kicks off CMake's compiler detection routines.

Next, we tell CMake that this project depends on the GTest package by issuing find_package(GTest REQUIRED). The REQUIRED argument kills the configure step if the package cannot be found. The name GTest is derived from the GTestConfig.cmake file. For any CMake project XYZ, its main package file must be named either XYZConfig.cmake or XYZ-config.cmake.

Finally, we add our test executable example and link it to the target GTest::gmock_main. This target provides a main function in addition to the GMock standard library. If you want to write your own main, then link to GTest::gmock instead.

^{1. with very few exceptions that are hardly worth mentioning}

Step 6: Building and running the example

Now we're finally ready to build and run the example. Let's go back up to our working directory:

alex:~/test/example$ cd ..
alex:~/test$

And now we'll go ahead and configure the build:

alex:~/test$ cmake -S example -B _build/example -DCMAKE_BUILD_TYPE=RelWithDebInfo -DCMAKE_PREFIX_PATH=$PWD/_local
-- The C compiler identification is GNU 9.4.0
-- The CXX compiler identification is GNU 9.4.0
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Check for working C compiler: /usr/bin/cc - skipped
-- Detecting C compile features
-- Detecting C compile features - done
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Check for working CXX compiler: /usr/bin/c++ - skipped
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Found GTest: /home/alex/test/_local/lib/cmake/GTest/GTestConfig.cmake (found version "1.11.0")
-- Configuring done
-- Generating done
-- Build files have been written to: /home/alex/test/_build/example

Note the -DCMAKE_PREFIX_PATH=$PWD/_local flag. That's telling CMake that there are additional libraries and CMake packages in $PWD/_local and so find_package and the other find_* commands should look there. If you didn't pass this flag, you might see an error like this:

CMake Error at /usr/share/cmake-3.23/Modules/FindPackageHandleStandardArgs.cmake:230 (message):
  Could NOT find GTest (missing: GTEST_LIBRARY GTEST_INCLUDE_DIR
  GTEST_MAIN_LIBRARY)
Call Stack (most recent call first):
  /usr/share/cmake-3.23/Modules/FindPackageHandleStandardArgs.cmake:594 (_FPHSA_FAILURE_MESSAGE)
  /usr/share/cmake-3.23/Modules/FindGTest.cmake:270 (FIND_PACKAGE_HANDLE_STANDARD_ARGS)
  CMakeLists.txt:4 (find_package)


-- Configuring incomplete, errors occurred!
See also "/home/alex/test/_build/example/CMakeFiles/CMakeOutput.log".

Now that we're configured, we can build the example:

alex:~/test$ cmake --build _build/example/
[ 50%] Building CXX object CMakeFiles/example.dir/main.cpp.o
[100%] Linking CXX executable example
[100%] Built target example

and then run it:

alex:~/test$ _build/example/example
Running main() from gmock_main.cc
[==========] Running 2 tests from 1 test suite.
[----------] Global test environment set-up.
[----------] 2 tests from Example
[ RUN      ] Example.AlwaysPass
[       OK ] Example.AlwaysPass (0 ms)
[ RUN      ] Example.AlwaysFail
/home/alex/test/example/main.cpp:8: Failure
Value of: 0
Expected: is equal to 1
  Actual: 0 (of type int)
[  FAILED  ] Example.AlwaysFail (0 ms)
[----------] 2 tests from Example (0 ms total)

[----------] Global test environment tear-down
[==========] 2 tests from 1 test suite ran. (0 ms total)
[  PASSED  ] 1 test.
[  FAILED  ] 1 test, listed below:
[  FAILED  ] Example.AlwaysFail

 1 FAILED TEST

As you can see, our passing test passed, and our failing test failed, as expected!

Step 6: CTest integration (optional)

If we want, we can integrate this with CTest for easier running of multiple GMock binaries down the line. Here's the new CMakeLists.txt

cmake_minimum_required(VERSION 3.23)
project(example)

enable_testing()              # ------------------------ ADDED 1

find_package(GTest REQUIRED)
include(GoogleTest)           # ------------------------ ADDED 2

add_executable(example main.cpp)
target_link_libraries(example PRIVATE GTest::gmock_main)

gtest_discover_tests(example) # ------------------------ ADDED 3

Aside from the three lines marked ADDED, nothing has changed. The first added line simply enables CTest support. The second added line imports CMake's native support for Google Test. Finally, the third line tells CTest that the example executable contains GTest tests.

After making these edits, an incremental build will automatically re-run CMake.

alex:~/test$ cmake --build _build/example/
-- Configuring done
-- Generating done
-- Build files have been written to: /home/alex/test/_build/example
Consolidate compiler generated dependencies of target example
[ 50%] Linking CXX executable example
[100%] Built target example

And now we can use the CTest runner on our build directory:

alex:~/test$ ctest --test-dir _build/example/
Internal ctest changing into directory: /home/alex/test/_build/example
Test project /home/alex/test/_build/example
    Start 1: Example.AlwaysPass
1/2 Test #1: Example.AlwaysPass ...............   Passed    0.00 sec
    Start 2: Example.AlwaysFail
2/2 Test #2: Example.AlwaysFail ...............***Failed    0.00 sec

50% tests passed, 1 tests failed out of 2

Total Test time (real) =   0.00 sec

The following tests FAILED:
          2 - Example.AlwaysFail (Failed)
Errors while running CTest
Output from these tests are in: /home/alex/test/_build/example/Testing/Temporary/LastTest.log
Use "--rerun-failed --output-on-failure" to re-run the failed cases verbosely.

And once again, we can see that our passing test passed and our failing test failed. Hooray!