Introduction to cmake and ninja
===============================
Cmake plus ninja is approximately equal to GNU autotools plus GNU
make, respectively. Both cmake and GNU autotools support self and
cross-compilation, checking for required components and versions.
- For a decent-sized project - such as vpp - build performance is drastically better with (cmake, ninja).
- The cmake input language looks like an actual language, rather than a shell scripting scheme on steroids.
- Ninja doesn't pretend to support manually-generated input files. Think of it as a fast, dumb robot which eats mildly legible byte-code.
See the `cmake website <http://cmake.org>`_, and the `ninja website
<https://ninja-build.org>`_ for additional information.
vpp cmake configuration files
-----------------------------
The top of the vpp project cmake hierarchy lives in .../src/CMakeLists.txt.
This file defines the vpp project, and (recursively) includes two kinds
of files: rule/function definitions, and target lists.
- Rule/function definitions live in .../src/cmake/{\*.cmake}. Although the contents of these files is simple enough to read, it shouldn't be necessary to modify them very often
- Build target lists come from CMakeLists.txt files found in subdirectories, which are named in the SUBDIRS list in .../src/CMakeLists.txt
::
##############################################################################
# subdirs - order matters
##############################################################################
if("${CMAKE_SYSTEM_NAME}" STREQUAL "Linux")
find_package(OpenSSL REQUIRED)
set(SUBDIRS
vppinfra svm vlib vlibmemory vlibapi vnet vpp vat vcl plugins
vpp-api tools/vppapigen tools/g2 tools/elftool tools/perftool)
elseif("${CMAKE_SYSTEM_NAME}" STREQUAL "Darwin")
set(SUBDIRS vppinfra)
else()
message(FATAL_ERROR "Unsupported system: ${CMAKE_SYSTEM_NAME}")
endif()
foreach(DIR ${SUBDIRS})
add_subdirectory(${DIR})
endforeach()
- The vpp cmake configuration hierarchy discovers the list of plugins to be built by searching for subdirectories in .../src/plugins which contain CMakeLists.txt files
::
##############################################################################
# find and add all plugin subdirs
##############################################################################
FILE(GLOB files RELATIVE
${CMAKE_CURRENT_SOURCE_DIR}
${CMAKE_CURRENT_SOURCE_DIR}/*/CMakeLists.txt
)
foreach (f ${files})
get_filename_component(dir ${f} DIRECTORY)
add_subdirectory(${dir})
endforeach()
How to write a plugin CMakeLists.txt file
-----------------------------------------
It's really quite simple. Follow the pattern:
::
add_vpp_plugin(mactime
SOURCES
mactime.c
node.c
API_FILES
mactime.api
INSTALL_HEADERS
mactime_all_api_h.h
mactime_msg_enum.h
API_TEST_SOURCES
mactime_test.c
)
Adding a target elsewhere in the source tree
--------------------------------------------
Within reason, adding a subdirectory to the SUBDIRS list in
.../src/CMakeLists.txt is perfectly OK. The indicated directory will
need a CMakeLists.txt file.
.. _building-g2:
Here's how we build the g2 event data visualization tool:
::
option(VPP_BUILD_G2 "Build g2 tool." OFF)
if(VPP_BUILD_G2)
find_package(GTK2 COMPONENTS gtk)
if(GTK2_FOUND)
include_directories(${GTK2_INCLUDE_DIRS})
add_vpp_executable(g2
SOURCES
clib.c
cpel.c
events.c
main.c
menu1.c
pointsel.c
props.c
g2version.c
view1.c
LINK_LIBRARIES vppinfra Threads::Threads m ${GTK2_LIBRARIES}
NO_INSTALL
)
endif()
endif()
The g2 component is optional, and is not built by default. There are
a couple of ways to tell cmake to include it in build.ninja [or in Makefile.]
When invoking cmake manually [rarely done and not very easy], specify
-DVPP_BUILD_G2=ON:
::
$ cmake ... -DVPP_BUILD_G2=ON
Take a good look at .../build-data/packages/vpp.mk to see where and
how the top-level Makefile and .../build-root/Makefile set all of the
cmake arguments. One strategy to enable an optional component is fairly
obvious. Add -DVPP_BUILD_G2=ON to vpp_cmake_args.
That would work, of course, but it's not a particularly elegant solution.
Tinkering with build options: ccmake
------------------------------------
The easy way to set VPP_BUILD_G2 - or frankly **any** cmake
parameter - is to install the "cmake-curses-gui" package and use
it.
- Do a straightforward vpp build using the top level Makefile, "make build" or "make build-release"
- Ajourn to .../build-root/build-vpp-native/vpp or .../build-root/build-vpp_debug-native/vpp
- Invoke "ccmake ." to reconfigure the project as desired
Here's approximately what you'll see:
::
CCACHE_FOUND /usr/bin/ccache
CMAKE_BUILD_TYPE
CMAKE_INSTALL_PREFIX /scratch/vpp-gate/build-root/install-vpp-nati
DPDK_INCLUDE_DIR /scratch/vpp-gate/build-root/install-vpp-nati
DPDK_LIB /scratch/vpp-gate/build-root/install-vpp-nati
MBEDTLS_INCLUDE_DIR /usr/include
MBEDTLS_LIB1 /usr/lib/x86_64-linux-gnu/libmbedtls.so
MBEDTLS_LIB2 /usr/lib/x86_64-linux-gnu/libmbedx509.so
MBEDTLS_LIB3 /usr/lib/x86_64-linux-gnu/libmbedcrypto.so
MUSDK_INCLUDE_DIR MUSDK_INCLUDE_DIR-NOTFOUND
MUSDK_LIB MUSDK_LIB-NOTFOUND
PRE_DATA_SIZE 128
VPP_API_TEST_BUILTIN ON
VPP_BUILD_G2 OFF
VPP_BUILD_PERFTOOL OFF
VPP_BUILD_VCL_TESTS ON
VPP_BUILD_VPPINFRA_TESTS OFF
CCACHE_FOUND: Path to a program.
Press [enter] to edit option Press [d] to delete an entry CMake Version 3.10.2
Press [c] to configure
Press [h] for help Press [q] to quit without generating
Press [t] to toggle advanced mode (Currently Off)
Use the cursor to point at the VPP_BUILD_G2 line. Press the return key
to change OFF to ON. Press "c" to regenerate build.ninja, etc.
At that point "make build" or "make build-release" will build g2. And so on.
Note that toggling advanced mode ["t"] gives access to substantially
all of the cmake option, discovered directories and paths.