cmake: find_package for architecture

Question

When cross-compiling, I am in the habit of using a toolchain file to specify (among other things) the CMAKE_SYSTEM_PROCESSOR .

In Ubuntu and other Linux distros, it seems to be able to install libraries intended for other architectures. For example, if I am working on an x86-64 machine, and want to install libpng for 64-bit ARM, then I would:

dpkg --add-architecture arm64
apt-get update
apt-get -y install libpng-dev:arm64

So after this, I have the libpng binaries for arm64. These seem to be installed in /usr/lib/aarch64-linux-gnu .

Now my understanding is that if I try to find the libpng in my CMakeLists.txt file (see CMake compile options for libpng ):

find_package(PNG REQUIRED)
include_directories(${PNG_INCLUDE_DIR})
target_link_libraries(example ${PNG_LIBRARY})

it will find the packages for the host machine (in this case x86-64), and not the target (arm64).

Is there a way to tell Cmake's find_package the target architecture? In the ideal case, find_package would examine CMAKE_SYSTEM_PROCESSOR before searching. I would like to know the easiest and most general way to handle this scenario since I am linking several libraries.

Right now the only method I am aware of is to hardcode the paths to the target libraries.

Answer 1

Modules like FindPNG.cmake use find_path and find_library to find all the things.

You can influence find_library by setting CMAKE_LIBRARY_ARCHITECTURE to aarch64-linux-gnu . Try just setting CMAKE_LIBRARY_ARCHITECTURE in your toolchain file.