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Hover-Jet

Look at the wiki for learning how to get started

Most of the commands in this file are copied from there. https://github.com/build-week/hover-jet/wiki

How to get the docker image

sudo apt-get update
sudo apt-get install apt-transport-https ca-certificates curl software-properties-common -y
curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add -
sudo apt-key fingerprint 0EBFCD88

# replace amd64 with armhf for odroid on this next line
sudo add-apt-repository "deb [arch=amd64] https://download.docker.com/linux/ubuntu $(lsb_release -cs) stable"

sudo apt-get update
sudo apt-get install docker-ce -y
sudo usermod -aG docker $USER


docker pull hoverjet/jet

How to Build

All compiling and running should be done inside the docker. There should be no exception to this. It's typically that managing git and editing files is done outside of the docker, on the host machine

How to build nominally

jet build <target>

jet run <bash command>

Using the shell inside the docker image (Sometimes useful for debugging)

Note: You should be using jet build or jet run, instead of these bash scripts

# Make sure the docker image is up to date
docker pull hoverjet/jet
# Enter the docker image
docker run -it -v ~/repos/hover-jet:/jet hoverjet/jet

Now, inside thedocker image

# Make sure you're in the docker image!!!!!!!
cd hover-jet

mkdir -p bin
cd bin
cmake ..
make -j7  # Where the 7 is the number of cores to use when building

Using our Build-System

Using Internal Libraries
  • If you include an internal library, the CMake dependencies and linking will automatically be determined
  • Such includes must be specified from the root of the repo
    • #include "infrastructure/comms/mqtt_subscriber.hh" instead of #include "mqtt_subscriber.hh"
    • Pymake only inspects "" includes, and ignores chevron includes, because chevrons are assumed to by system or external libs
  • What if internal library isn't inspected by pymake? (Say it's been intentionally ignored, or has its own CMakeLists)
    • Then you must manually specify, in either the .hh or .cc of your library, %deps(the_lib_i_want)
Using External Libraries
  • Third party libraries are typically not auto-linked through pymake, though this is an upcoming feature.
  • Instead, we must manually specify dependencies
  • Examples:
    • %deps(opengl, glfw), %deps(opencv)
Defining Libraries

  • A library target will be generated when a .hh and .cc file have the same name

    • For example: my_lib.hh, and my_lib.cc
    • The library will be called my_lib
    • All library names must be unique (This is, in principle, a CMake limitation)

  • An implicit header-only library will be discovered whenever only a .hh exists

    • Things that include the header-only library will implicitly link against libraries used by the header-only lib
Defining Executables
  • If your file contains a main function, an executable will be generated
  • If your file contains "// %binary", an executable will be generated
Adding a third-party library
  • Header-only libraries can be simply plopped into the third_party folder, and then
    • include_directories("${CMAKE_CURRENT_SOURCE_DIR}/third_party/lib") placed in the top-level CMakeLists.txt
      • Sometimes you have to be clever with the above command
  • Libraries that require some compilation are tricky. In order of decreasing ease:
    • apt-package
    • compile from source and make install
    • include it in our repo, and munge its CMake chain to work with ours; This can often be very difficult
Debugging

  • My thing isn't getting built!

    • Look at /tmp/CMakeLists.txt, and check that add_library(my_lib) or add_executable(my_exec) exists
    • Make sure that when cmake .. is run, there is no error generated. Sometimes it will be buried in a bit of text
    • Is there a // %ignore in your file (Check both the header and cc!)
    • Do pymake -v info in the hover-jet directory, and make sure your file is getting discovered

  • My build takes a long time

    • The cmake cache gets invalidated often
    • Try make -j3 <just_the_target_i_want>, and rely on CI to asynchronously build everything

  • There's a weird target already exists error, or something like it

    • This usually happens because your library name is not globally unique. Keep in mind, CMake effectively requires all library names to be globally unique.
    • If this is a big problem, we can use pymake to auto-generate unique library names

  • There's a header XXXXXX.hh unknown in YYYYYY.cc

    • Usually, this means YYYYYY.cc is including a header that isn't real
    • If it's an external library that isn't in our repository, use <> includes, then pymake won't require its existence
    • Make sure the #include path is from the root of the repo, and not relative
      • #include "infrastructure/comms/mqtt_subscriber.hh" instead of #include "mqtt_subscriber.hh"

  • No definition for XXXX error, or could not find library -lmy_library, or failed to link

    • This is usually because %deps() is being used for a library name that doesn't exist
      • If it's external, check ldconfig -p | grep <lib_name_I_expect_to_exist>
        • If ldconfig has the lib, but you still see the error, you must add find_package(lib-name) in the top-level CMake
      • If it's internal, try git grep -rni "add_library(lib_name_I_expect_to_exist" (With the closing parenthesis excluded)
      • If these are not the case, go find Jake, this is a bug