Examples fail to build

[rossburton]

With protobuf main as of 68bd6be, if I build with -Dprotobuf_BUILD_EXAMPLES=ON and then try and build the examples target:

$ ninja -C build examples
ninja: Entering directory `build'
[1/4] Performing configure step for 'examples'
FAILED: examples/logs/examples-configure /home/rosbur01/Code/drive-by/protobuf/build/examples/logs/examples-configure
cd /home/rosbur01/Code/drive-by/protobuf/build/examples && /usr/bin/cmake -P /home/rosbur01/Code/drive-by/protobuf/build/examples/logs/examples-configure-.cmake && /usr/bin/cmake -E touch /home/rosbur01/Code/drive-by/protobuf/build/examples/logs/examples-configure
CMake Error at logs/examples-configure-.cmake:49 (message):
  Command failed: 1

   '/usr/bin/cmake' '-GNinja' '-C/home/rosbur01/Code/drive-by/protobuf/build/examples/tmp/examples-cache-.cmake' '-S' '/home/rosbur01/Code/drive-by/protobuf/examples' '-B' '/home/rosbur01/Code/drive-by/protobuf/build/examples'

  See also

    /home/rosbur01/Code/drive-by/protobuf/build/examples/logs/examples-configure-*.log


ninja: build stopped: subcommand failed.

Am I doing something wrong?

[rossburton]

Ah, actually looked in the log file.

CMake Error at CMakeLists.txt:8 (find_package):
  Could not find a package configuration file provided by "protobuf" with any
  of the following names:

    protobufConfig.cmake
    protobuf-config.cmake

  Add the installation prefix of "protobuf" to CMAKE_PREFIX_PATH or set
  "protobuf_DIR" to a directory containing one of the above files.  If
  "protobuf" provides a separate development package or SDK, be sure it has
  been installed.

It looks like the examples.cmake is trying to make the examples use the just-built protobuf with this:

add_examples_build(examples "-Dprotobuf_DIR:PATH=${CMAKE_BINARY_DIR}/${CMAKE_INSTALL_CMAKEDIR}")

But obviously that isn't actually working.

[rossburton]

So ${CMAKE_BINARY_DIR}/${CMAKE_INSTALL_CMAKEDIR} is .../build/lib/cmake/protobuf but that's not right, the /lib/ doesn't exist in the build tree.

If I hardcode the right path (${CMAKE_BINARY_DIR}/cmake/protobuf) then it fails differently:

CMake Error at /home/rosbur01/Code/drive-by/protobuf/build/cmake/protobuf/protobuf-config.cmake:16 (include):
  include could not find requested file:

    /home/rosbur01/Code/drive-by/protobuf/build/cmake/protobuf/protobuf-targets.cmake

If I search for that file then it's only found buried in the build tree:

$ find . -name protobuf-targets.cmake
./build/CMakeFiles/Export/5a0f10ea4324979995731323bb365f6f/protobuf-targets.cmake

[esrauchg]

Sam may need to look closer but initial triage suggested that this is more likely a 'documentation is bad' kind of bug resulting in 'holding it wrong' and that the proper way to build the examples involves some different arg for the installed protobuf.