Getting things to work with CMake's FetchContent

[unindented]

In my C++ projects, I'm used to including libraries like googletest and catch2 using FetchContent functionality in CMake:

FetchContent_Declare(
  catch2
  GIT_REPOSITORY https://github.com/catchorg/Catch2.git
  GIT_TAG        v2.10.2
)
FetchContent_MakeAvailable(catch2)

target_link_libraries(mytests PRIVATE myapp Catch2::Catch2)

I haven't been able to get a similar setup working with check. If I do something like this:

FetchContent_Declare(
  check
  GIT_REPOSITORY https://github.com/libcheck/check.git
  GIT_TAG        0.13.0
)
FetchContent_MakeAvailable(check)

target_link_libraries(mytests PRIVATE myapp Check::check)

I get this error:

CMake Error at tests/CMakeLists.txt:10 (add_executable):
  Target "loxtest" links to target "Check::check" but the target was not
  found.  Perhaps a find_package() call is missing for an IMPORTED target, or
  an ALIAS target is missing?

What am I doing wrong?

[mikkoi]

Check tries to be compatible with CMake but importing the project this way fails. Checked it myself.
You need to build check by itself. No need to install.
Then use find_package() to find it.

When building check (cmake

&& make), CMake registers the build in Package Registry (~/.cmake/package/). find_package() uses this.

Using ExternalProject_Add() in CMake might work (have not tested) because it builds the project independently from your main project and "installs" it in the build tree.

[unindented]

What would it take for Check to be compatible with FetchContent? It's super convenient for the consumer.

[mikkoi]

It certainly looks convenient. I'll take a look at it. For the time being Check needs to retain compatibility with GNU Autotools and that poses some challenges.

[mikkoi]

I believe I added the necessary parts. Please try with branch mikkoi:fix-for-cmake-fetchcontent, pull request #239 if it works for you aswell.

[unindented]

@mikkoi thank you!

When I point FetchContent to your branch, CMake seems to complain about a submodule in the tests/ folder:

[ 11%] Performing download step (git clone) for 'check-populate'
Cloning into 'check-src'...
Note: switching to 'origin/fix-for-cmake-fetchcontent'.

You are in 'detached HEAD' state. You can look around, make experimental
changes and commit them, and you can discard any commits you make in this
state without impacting any branches by switching back to a branch.

If you want to create a new branch to retain commits you create, you may
do so (now or later) by using -c with the switch command. Example:

  git switch -c <new-branch-name>

Or undo this operation with:

  git switch -

Turn off this advice by setting config variable advice.detachedHead to false

HEAD is now at f8e5822 Add Travis build: using Check in CMake build
fatal: No url found for submodule path 'tests/cmake_project_usage_test' in .gitmodules
CMake Error at check-subbuild/check-populate-prefix/tmp/check-populate-gitclone.cmake:49 (message):
  Failed to update submodules in:
  '/Users/dania/Code/lox-c/cmake-build-debug/_deps/check-src'


make[2]: *** [check-populate-prefix/src/check-populate-stamp/check-populate-download] Error 1
make[1]: *** [CMakeFiles/check-populate.dir/all] Error 2
make: *** [all] Error 2

CMake Error at /Applications/CLion.app/Contents/bin/cmake/mac/share/cmake-3.15/Modules/FetchContent.cmake:915 (message):
  Build step for check failed: 2
Call Stack (most recent call first):
  /Applications/CLion.app/Contents/bin/cmake/mac/share/cmake-3.15/Modules/FetchContent.cmake:1006 (__FetchContent_directPopulate)
  /Applications/CLion.app/Contents/bin/cmake/mac/share/cmake-3.15/Modules/FetchContent.cmake:1047 (FetchContent_Populate)
  tests/CMakeLists.txt:7 (FetchContent_MakeAvailable)


-- Configuring incomplete, errors occurred!

Do you know what that's about.

[mikkoi]

Hups! When creating the test, I used a separate git repo. When importing the code into Check, I accidentally copied the .git directory too, and committed it. Git thought it was an included git repo. I have pushed a fix.

[unindented]

Awesome, now everything builds successfully!

The only weird thing is that CMake is including Check's test targets (check_set_max_msg_size, check_nofork_teardown, etc.) as part of my build:

$ cmake --build .
Scanning dependencies of target myapp
[  1%] Building C object src/CMakeFiles/myapp.dir/lib.c.o
[  2%] Linking C static library libmyapp.a
[  2%] Built target myapp
Scanning dependencies of target myappapp
[  4%] Building C object apps/CMakeFiles/myappapp.dir/app.c.o
[  5%] Linking C executable myappapp
[  5%] Built target myappapp
Scanning dependencies of target check
[  6%] Building C object _deps/check-build/src/CMakeFiles/check.dir/check.c.o
[  8%] Building C object _deps/check-build/src/CMakeFiles/check.dir/check_error.c.o
[  9%] Building C object _deps/check-build/src/CMakeFiles/check.dir/check_list.c.o
[ 11%] Building C object _deps/check-build/src/CMakeFiles/check.dir/check_log.c.o
[ 12%] Building C object _deps/check-build/src/CMakeFiles/check.dir/check_msg.c.o
[ 13%] Building C object _deps/check-build/src/CMakeFiles/check.dir/check_pack.c.o
[ 15%] Building C object _deps/check-build/src/CMakeFiles/check.dir/check_print.c.o
[ 16%] Building C object _deps/check-build/src/CMakeFiles/check.dir/check_run.c.o
[ 18%] Building C object _deps/check-build/src/CMakeFiles/check.dir/check_str.c.o
[ 19%] Building C object _deps/check-build/src/CMakeFiles/check.dir/__/lib/fpclassify.c.o
[ 20%] Building C object _deps/check-build/src/CMakeFiles/check.dir/__/lib/clock_gettime.c.o
[ 22%] Building C object _deps/check-build/src/CMakeFiles/check.dir/__/lib/timer_create.c.o
[ 23%] Building C object _deps/check-build/src/CMakeFiles/check.dir/__/lib/timer_delete.c.o
[ 25%] Building C object _deps/check-build/src/CMakeFiles/check.dir/__/lib/timer_settime.c.o
[ 26%] Linking C static library libcheck.a
[ 26%] Built target check
Scanning dependencies of target myapptest
[ 27%] Building C object tests/CMakeFiles/myapptest.dir/testlib.c.o
[ 29%] Linking C executable myapptest
[ 29%] Built target myapptest
Scanning dependencies of target compat
[ 30%] Building C object _deps/check-build/lib/CMakeFiles/compat.dir/libcompat.c.o
[ 31%] Building C object _deps/check-build/lib/CMakeFiles/compat.dir/fpclassify.c.o
[ 33%] Building C object _deps/check-build/lib/CMakeFiles/compat.dir/clock_gettime.c.o
[ 34%] Building C object _deps/check-build/lib/CMakeFiles/compat.dir/timer_create.c.o
[ 36%] Building C object _deps/check-build/lib/CMakeFiles/compat.dir/timer_delete.c.o
[ 37%] Building C object _deps/check-build/lib/CMakeFiles/compat.dir/timer_settime.c.o
[ 38%] Linking C static library libcompat.a
[ 38%] Built target compat
Scanning dependencies of target checkShared
[ 40%] Building C object _deps/check-build/src/CMakeFiles/checkShared.dir/check.c.o
[ 41%] Building C object _deps/check-build/src/CMakeFiles/checkShared.dir/check_error.c.o
[ 43%] Building C object _deps/check-build/src/CMakeFiles/checkShared.dir/check_list.c.o
[ 44%] Building C object _deps/check-build/src/CMakeFiles/checkShared.dir/check_log.c.o
[ 45%] Building C object _deps/check-build/src/CMakeFiles/checkShared.dir/check_msg.c.o
[ 47%] Building C object _deps/check-build/src/CMakeFiles/checkShared.dir/check_pack.c.o
[ 48%] Building C object _deps/check-build/src/CMakeFiles/checkShared.dir/check_print.c.o
[ 50%] Building C object _deps/check-build/src/CMakeFiles/checkShared.dir/check_run.c.o
[ 51%] Building C object _deps/check-build/src/CMakeFiles/checkShared.dir/check_str.c.o
[ 52%] Building C object _deps/check-build/src/CMakeFiles/checkShared.dir/__/lib/fpclassify.c.o
[ 54%] Building C object _deps/check-build/src/CMakeFiles/checkShared.dir/__/lib/clock_gettime.c.o
[ 55%] Building C object _deps/check-build/src/CMakeFiles/checkShared.dir/__/lib/timer_create.c.o
[ 56%] Building C object _deps/check-build/src/CMakeFiles/checkShared.dir/__/lib/timer_delete.c.o
[ 58%] Building C object _deps/check-build/src/CMakeFiles/checkShared.dir/__/lib/timer_settime.c.o
[ 59%] Linking C shared library libcheck.dylib
[ 59%] Built target checkShared
Scanning dependencies of target check_set_max_msg_size
[ 61%] Building C object _deps/check-build/tests/CMakeFiles/check_set_max_msg_size.dir/check_set_max_msg_size.c.o
[ 62%] Linking C executable check_set_max_msg_size
[ 62%] Built target check_set_max_msg_size
Scanning dependencies of target ex_output
[ 63%] Building C object _deps/check-build/tests/CMakeFiles/ex_output.dir/ex_output.c.o
[ 65%] Linking C executable ex_output
[ 65%] Built target ex_output
Scanning dependencies of target check_nofork_teardown
[ 66%] Building C object _deps/check-build/tests/CMakeFiles/check_nofork_teardown.dir/check_nofork_teardown.c.o
[ 68%] Linking C executable check_nofork_teardown
[ 68%] Built target check_nofork_teardown
Scanning dependencies of target check_nofork
[ 69%] Building C object _deps/check-build/tests/CMakeFiles/check_nofork.dir/check_nofork.c.o
[ 70%] Linking C executable check_nofork
[ 70%] Built target check_nofork
Scanning dependencies of target check_check_export
[ 72%] Building C object _deps/check-build/tests/CMakeFiles/check_check_export.dir/check_check_sub.c.o
[ 73%] Building C object _deps/check-build/tests/CMakeFiles/check_check_export.dir/check_check_master.c.o
[ 75%] Building C object _deps/check-build/tests/CMakeFiles/check_check_export.dir/check_check_log.c.o
[ 76%] Building C object _deps/check-build/tests/CMakeFiles/check_check_export.dir/check_check_fork.c.o
[ 77%] Building C object _deps/check-build/tests/CMakeFiles/check_check_export.dir/check_check_export_main.c.o
[ 79%] Linking C executable check_check_export
[ 79%] Built target check_check_export
Scanning dependencies of target check_check
[ 80%] Building C object _deps/check-build/tests/CMakeFiles/check_check.dir/check_check_exit.c.o
[ 81%] Building C object _deps/check-build/tests/CMakeFiles/check_check.dir/check_check_fixture.c.o
[ 83%] Building C object _deps/check-build/tests/CMakeFiles/check_check.dir/check_check_fork.c.o
[ 84%] Building C object _deps/check-build/tests/CMakeFiles/check_check.dir/check_check_limit.c.o
[ 86%] Building C object _deps/check-build/tests/CMakeFiles/check_check.dir/check_check_log.c.o
[ 87%] Building C object _deps/check-build/tests/CMakeFiles/check_check.dir/check_check_log_internal.c.o
[ 88%] Building C object _deps/check-build/tests/CMakeFiles/check_check.dir/check_check_main.c.o
[ 90%] Building C object _deps/check-build/tests/CMakeFiles/check_check.dir/check_check_master.c.o
[ 91%] Building C object _deps/check-build/tests/CMakeFiles/check_check.dir/check_check_msg.c.o
[ 93%] Building C object _deps/check-build/tests/CMakeFiles/check_check.dir/check_check_pack.c.o
[ 94%] Building C object _deps/check-build/tests/CMakeFiles/check_check.dir/check_check_selective.c.o
[ 95%] Building C object _deps/check-build/tests/CMakeFiles/check_check.dir/check_check_sub.c.o
[ 97%] Building C object _deps/check-build/tests/CMakeFiles/check_check.dir/check_check_tags.c.o
[ 98%] Building C object _deps/check-build/tests/CMakeFiles/check_check.dir/check_list.c.o
[100%] Linking C executable check_check
[100%] Built target check_check

And running ctest runs not just my tests, but also Check's (check_check):

$ ctest
Test project /Users/daniel/Code/myapp-c/build
      Start  1: tests
 1/10 Test  #1: tests ............................   Passed    0.00 sec
      Start  2: check_check
...

The relevant part of my CMakeLists.txt looks like this, in case I'm doing something wrong:

FetchContent_Declare(
  check
  GIT_REPOSITORY https://github.com/mikkoi/check.git
  GIT_TAG        origin/fix-for-cmake-fetchcontent
)

FetchContent_MakeAvailable(check)

add_executable(myapptest testlib.c ${HEADER_LIST})

target_compile_features(myapptest PRIVATE c_std_11)

target_link_libraries(myapptest PRIVATE myapp Check::check)

add_test(NAME tests COMMAND myapptest)

[mikkoi]

I noticed the same thing earlier with my test. I tried with my own real project rubik, not just the tests/cmake_project_usage_test. I suspect it is supposed to do that. FetchContent makes Check part of the using project, instead of just using a separately compiled Check installation, e.g. with ExternalProject or plain find_package(). Another thing that happens is that the using project's settings become Check's now, so for instance if you turn on all possible alarms a compiler can generate, Check will give out some programming style related warnings. I noticed this because my own project is using several static analysis checks.

[unindented]

Ah, interesting. Do you know why catch2 or googletest don't behave the same?

[mikkoi]

I just took a quick look at Catch2 and I noticed it does not rely solely on CMake's common way. It has this:

# detect if Catch is being bundled,
# disable testsuite in that case
if(NOT DEFINED PROJECT_NAME)
  set(NOT_SUBPROJECT ON)
endif()
[..]
option(CATCH_BUILD_TESTING "Build SelfTest project" ON)
[..]
if (BUILD_TESTING AND CATCH_BUILD_TESTING AND NOT_SUBPROJECT)

Check maybe needs more adapting...