... because it is (required).
This makes a difference when building with CMake and forgetting
ZEPHYR_BASE or not registering Zephyr in the CMake package registry.
In this particular case, REQUIRED turns this harmless looking log
statement:
-- Could NOT find Zephyr (missing: Zephyr_DIR)
-- The C compiler identification is GNU 9.3.0
-- The CXX compiler identification is GNU 9.3.0
-- Check for working C compiler: /usr/bin/cc
-- ...
-- ...
-- ...
-- Detecting CXX compile features
-- Detecting CXX compile features - done
CMake Error at CMakeLists.txt:8 (target_sources):
Cannot specify sources for target "app" which is not built by
this project.
... into this louder, clearer, faster and (last but not least) final
error:
CMake Error at CMakeLists.txt:5 (find_package):
Could not find a package configuration file provided by "Zephyr" with
any of the following names:
ZephyrConfig.cmake
zephyr-config.cmake
Add the installation prefix of "Zephyr" to CMAKE_PREFIX_PATH or set
"Zephyr_DIR" to a directory containing one of the above files. If
"Zephyr" provides a separate development package or SDK, be sure it
has been installed.
-- Configuring incomplete, errors occurred!
Signed-off-by: Marc Herbert <marc.herbert@intel.com>
Using find_package to locate Zephyr.
Old behavior was to use $ENV{ZEPHYR_BASE} for inclusion of boiler plate
code.
Whenever an automatic run of CMake happend by the build system / IDE
then it was required that ZEPHYR_BASE was defined.
Using ZEPHYR_BASE only to locate the Zephyr package allows CMake to
cache the base variable and thus allowing subsequent invocation even
if ZEPHYR_BASE is not set in the environment.
It also removes the risk of strange build results if a user switchs
between different Zephyr based project folders and forgetting to reset
ZEPHYR_BASE before running ninja / make.
Signed-off-by: Torsten Rasmussen <Torsten.Rasmussen@nordicsemi.no>
Marc Herbert