CMake target_link_libraries() scopes example

An example of particular effects from PRIVATE/INTERFACE/PUBLIC scope in CMake's target_link_libraries().

More details in the following article.

Unlike the code fragments in the article, the prjct here handles linking scope via THINGY_LINKING cache variable, for example -DTHINGY_LINKING="INTERFACE". Based on that, certain target properties are set and carried over, changing certain compile definitions, making the compilation to account for the current linking scope "automatically" (so you don't need to modify the sources yourself).

Building

It is 3 projects that are built individually and in particular order:

1. dpndnc - a library made to be a direct dependency of prjct;
2. prjct - a project with two libraries, one of which directly depends on dpndnc;
3. tl - a CLI tool that directly depends on prjct libraries and also transitively depends on dpndnc.

dpndnc

$ cd /path/to/cmake-target-link-libraries-example/dpndnc
$ mkdir build && cd $_
$ cmake -G Ninja -DCMAKE_BUILD_TYPE=Release -DCMAKE_INSTALL_PREFIX="../install" ..
$ cmake --build . --target install

prjct

$ cd /path/to/cmake-target-link-libraries-example/prjct
$ mkdir build && cd $_
$ cmake -G Ninja -DCMAKE_BUILD_TYPE=Release -DCMAKE_INSTALL_PREFIX="../install" \
    -DCMAKE_PREFIX_PATH="/path/to/cmake-target-link-libraries-example/dpndnc/install" \
    -DTHINGY_LINKING="INTERFACE" \
    ..
$ cmake --build . --target install

tl

$ cd /path/to/cmake-target-link-libraries-example/tl
$ mkdir build && cd $_
$ cmake -G Ninja -DCMAKE_BUILD_TYPE=Release -DCMAKE_INSTALL_PREFIX="../install" \
    -DCMAKE_PREFIX_PATH="/path/to/cmake-target-link-libraries-example/prjct/install;/path/to/cmake-target-link-libraries-example/dpndnc/install" \
    ..
$ cmake --build . --target install
$ ../install/bin/some-tool