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Update to minimum CMake 3.5

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And modernise some examples.
This commit is contained in:
Thom Troy
2018-03-18 17:23:57 +00:00
parent 54e75664c1
commit b81da6f68b
52 changed files with 303 additions and 212 deletions
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50
01-basic/H-third-party-library/README.adoc
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@@ -85,33 +85,63 @@ variable, these are package specific and are typically documented at the top of
The variables exported in this example include:
* `Boost_INCLUDE_DIRS` - The path to the boost header files.
* `Boost_SYSTEM_LIBRARY` - The path to the boost system library.
* `Boost_FILESYSTEM_LIBRARY` - The path to the boost filesystem library.
In some cases you can also check these variables by examining the cache using
ccmake or cmake-gui.
## Alias variables
## Alias / Imported targets
Some modern CMake libraries export +ALIAS+ targets in their module files. For example, starting from v3.5+ of CMake, the
Most modern CMake libraries link:https://cmake.org/cmake/help/v3.6/prop_tgt/IMPORTED.html#prop_tgt:IMPORTED[export] +ALIAS+ targets in their module files.
The benefit of imported targets are that they can also populate include directories and linked libraries.
For example, starting from v3.5+ of CMake, the
Boost module supports this. Similar to using your own ALIAS target for libraires, an +ALIAS+ in a module can make referencing found targets eaiser.
In the case of Boost, you could replace the following from this example:
In the case of Boost, all targets are exported using the `Boost::` identifier and then the name
of the subsystem. For example you can use:
* `Boost_INCLUDE_DIRS` with `Boost::boost` for header only libraries
* `Boost_FILESYSTEM_LIBRARY` with `Boost::filesystem`
* `Boost_SYSTEM_LIBRARY` with `Boost::system`. If you include `Boost::filesystem` it automatically includes `Boost::system`
* `Boost::boost` for header only libraries
* `Boost::system` for the boost system library.
* `Boost::filesystem` for filesystem library.
Using the new alias sytem, to replicate this example you only have to link the following:
As with your own targets, these targets include their dependencies, so linking against
`Boost::filesystem` will automatically add `Boost::boost` and `Boost::system` dependencies.
To link against an imported target you can use the following:
[source,cmake]
----
target_link_libraries( third_party_include
PRIVATE
Boost::filesystem
Boost::filesystem
)
----
## Non-alias targets
While most modern libraries use imported targets, not all modules have been updated. In the
case where a library hasn't been updated you will often find the following variables available:
* xxx_INCLUDE_DIRS - A varialble pointing to the include directory for the library.
* xxx_LIBRARY - A variable pointing to the library path.
These can then be added to your +target_include_directories+ and +target_link_libraries+ as:
[source,cmake]
----
# Include the boost headers
target_include_directories( third_party_include
PRIVATE ${Boost_INCLUDE_DIRS}
)
# link against the boost libraries
target_link_libraries( third_party_include
PRIVATE
${Boost_SYSTEM_LIBRARY}
${Boost_FILESYSTEM_LIBRARY}
)
----
# Building the Example
[source,bash]