CODEWITHSUNDEEP
cmake
rafoo
rafoo

Reputation: 1642

Is it possible to call a custom CMake function when library is linked?

Let's say I have a library A and a project B which uses A.

project(libA)

function(calledWhenLink target)
    message(STATUS Hi ${target}) # Should print "Hi exeB"
endfunction()

add_library(libA INTERFACE)

project(exeB)

find_package(A REQUIRED)
target_link_library(exeB libA)

Is it possible to automatically call calledWhenLink() when the executable links to the library ?

Reasoning: As said in a comment, the original problem is that VTK needs to call CMake vtk_module_autoinit. My library uses VTK, and it seems better for all the samples to automatically call this when linked to the lib instead of copy paste the code in each CMakeLists. The problem is that vtk_module_autoinit is not working when called with the lib target instead ot the exe in my tests.

Upvotes: 0

Views: 142

Answers (1)

Alex Reinking
Alex Reinking

Reputation: 20026

Yes, it is possible to run arbitrary CMake code at build time. However, it is not at all clear what you're really trying to do, so this might not be a good approach.

Here's a minimal example:

cmake_minimum_required(VERSION 3.21)
project(example)

file(WRITE "${CMAKE_CURRENT_BINARY_DIR}/post-link.cmake" [[
message(STATUS "Hi ${target}")
]])

add_executable(exeB main.cpp)
add_custom_command(
  TARGET exeB POST_BUILD
  COMMAND "${CMAKE_COMMAND}"
          -Dtarget=exeB
          -P "${CMAKE_CURRENT_BINARY_DIR}/post-link.cmake" 
)

Test interaction:

alex@alex-ubuntu:~/test$ cmake -G Ninja -S . -B build
-- The C compiler identification is GNU 9.3.0
-- The CXX compiler identification is GNU 9.3.0
-- 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
-- Configuring done
-- Generating done
-- Build files have been written to: /home/alex/test/build
alex@alex-ubuntu:~/test$ cmake --build build/ --verbose
[1/2] /usr/bin/c++    -MD -MT CMakeFiles/exeB.dir/main.cpp.o -MF CMakeFiles/exeB.dir/main.cpp.o.d -o CMakeFiles/exeB.dir/main.cpp.o -c /home/alex/test/main.cpp
[2/2] : && /usr/bin/c++   CMakeFiles/exeB.dir/main.cpp.o -o exeB   && cd /home/alex/test/build && /usr/bin/cmake -Dtarget=exeB -P /home/alex/test/build/post-link.cmake
-- Hi exeB

Upvotes: 1

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