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update some examples to require cmake v3

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Thom Troy
2016-08-17 00:09:36 +01:00
parent 3335200e43
commit 90013579f9
16 changed files with 123 additions and 47 deletions
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62
02-sub-projects/A-basic/README.adoc
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@@ -63,14 +63,12 @@ add_subdirectory(subbinary)
When a project is created using the `project()` command, CMake will automatically
create a number of variables which can be used to reference details about the project.
These variables can then be used by other sub-projects or the main project. For exampe,
to include header files between projects.
to reference the source directory for a different project you can use.
[source,cmake]
----
include_directories(
${sublibrary1_SOURCE_DIR}/inc
${sublibrary2_SOURCE_DIR}/inc
)
${sublibrary1_SOURCE_DIR}
${sublibrary2_SOURCE_DIR}
----
The variables created by CMake include:
@@ -97,6 +95,28 @@ In this example the binary directories created would be `sublibrary1_BINARY_DIR`
|=======================================================================
## Header only Libraries
If you have a library that is created as a header only library, cmake supports the +INTERFACE+
target to allow creating a target without any build output. More details can be found from
link:https://cmake.org/cmake/help/v3.4/command/add_library.html#interface-libraries[here]
[source,cmake]
----
add_library(${PROJECT_NAME} INTERFACE)
----
When creating the target you can also include directories for that target using
the +INTERFACE+ scope. The +INTERFACE+ scope is use to make target requirements that are used in any Libraries
that link this target but not in the complation of the target itself.
[source,cmake]
----
target_include_directories(${PROJECT_NAME}
INTERFACE
${PROJECT_SOURCE_DIR}/inc
)
----
## Referencing Libraries from Sub-Projects
@@ -108,10 +128,42 @@ is added as a dependency.
[source,cmake]
----
target_link_libraries(subbinary
PUBLIC
sublibrary1
)
----
Alternatively, you can create an alias target which allows you to reference the
target in read only contexts.
To create an alias target run:
[source,cmake]
----
add_library(sublibrary2)
add_library(sub::lib2 ALIAS sublibrary2)
----
To reference the alias, just it as follows:
[source,cmake]
----
target_link_libraries(subbinary
sublibrary1
)
----
## Include directories from sub-projects
When adding the libraries from the sub-projects, starting from cmake v3, there is
no need to add the projects include directores in the include directories of the
binary using them.
This is controlled by the scope in the `target_include_directories()` command when creating
the libraries. In this example because the subbinary executable links the sublibrary1
and sublibrary2 libraries it will automatically include the `${sublibrary1_SOURCE_DIR}/inc`
and `${sublibrary2_SOURCE_DIR}/inc` folders as they are exported with the
+PUBLIC+ and +INTERFACE+ scopes of the libraries.
# Building the example
[source,bash]