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<font size=5>The following example </font> demonstrates some key ideas
of CMake. (You may wish to download this
<a href="/CMake/HTML/cmakeExample.tar.gz">example code</a> and try it
out for yourself.) Make sure that you have CMake installed prior to
running this example (go <a href="/CMake/HTML/Install.html">here</a>
for instructions).
<p>
There are three directories involved. The top level directory has two
subdirectories called ./Demo and ./Hello. In the directory ./Hello, a
library is built. In the directory ./Demo, an executable is built by
linking to the library. A total of three CMakeList.txt files are
created: one for each directory.
<p>
The first, top-level directory contains the following CMakeLists.txt file.
<pre>
# The name of our project is "HELLO". CMakeLists files in this project can
# refer to the root source directory of the project as ${HELLO_SOURCE_DIR} and
# to the root binary directory of the project as ${HELLO_BINARY_DIR}.
PROJECT(HELLO)
# Recurse into the "Hello" and "Demo" subdirectories. This does not actually
# cause another cmake executable to run. The same process will walk through
# the project's entire directory structure.
SUBDIRS(Hello Demo)
</pre>
Then for each subdirectory listed in the SUBDIRS command, CMakeLists.txt
files are created. In the ./Hello directory, the following CMakeLists.txt
file is created:
<pre>
# Create a library called "Hello" which includes the source file "hello.cxx".
# The extension is already found. Any number of sources could be listed here.
ADD_LIBRARY(Hello hello)
</pre>
Finally, in the ./Demo directory, the third and final CMakeLists.txt file
is created:
<pre>
# Make sure the compiler can find include files from our Hello library.
INCLUDE_DIRECTORIES(${HELLO_SOURCE_DIR}/Hello)
# Make sure the linker can find the Hello library once it is built.
LINK_DIRECTORIES(${HELLO_BINARY_DIR}/Hello)
# Add executable called "helloDemo" that is built from the source files
# "demo.cxx" and "demo_b.cxx". The extensions are automatically found.
ADD_EXECUTABLE(helloDemo demo demo_b)
# Link the executable to the Hello library.
TARGET_LINK_LIBRARIES(helloDemo Hello)
</pre>
CMake when executed in the top-level directory will process the
CMakeLists.txt file and then descend into the listed subdirectories.
Variables, include paths, library paths, etc. are inherited. Depending
on the system, makefiles (Unix) or workspaces/projects (MSVC) will be
built. These can then be used in the usual way to build the code.
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