Automatic builds¶

No dependencies in README¶

Build instructions from Hunter archive triggered automatically when hunter_add_package function called. Hence there is no need to specify dependencies in a raw README file like:

For OSX please do:
> brew install foo boo

For Ubuntu please do:
> sudo apt-get install foo boo

Then run build:
> cmake -H. -B_builds
> cmake --build _builds

Now it’s simply:

Just run build:
> cmake -H. -B_builds # dependencies installed automatically
> cmake --build _builds

Optional dependencies¶

Optional dependency? No problems, expressed in a pretty clean way:

# required dependencies
hunter_add_package(foo)
hunter_add_package(boo)
if(BUILD_WITH_BAR)
  hunter_add_package(bar)
endif()

Same commands:

> cmake -H. -B_builds -DBUILD_WITH_BAR=YES # + install bar

instead of:

Additionally if you want bar support please run:
> brew install bar # OSX
> sudo apt-get install bar # Ubuntu

Then run build:
> cmake -H. -B_builds -DBUILD_WITH_BAR=YES

Vs. ‘requirements.txt’ style¶

Note that such approach differs from requirements.txt-like approach (i.e. when external packages specified by separate file). This allow to avoid duplication of logic in many cases even if requirements.txt do downloads automatically too.

Imagine we have to specify dependencies in some kind of requirements.cmake file and there is user’s option:

# requirements.cmake

if(WIN32 AND BUILD_WITH_BAR)
  command_to_install(Bar)
endif()

In case it’s not CMake code this will look even fancy, say requirements.json:

{
  "dependencies":
  {
    "package": "Bar",
    "platform": "windows",
    "cmake option": "BUILD_WITH_BAR"
  }
}

You have to repeat same condition in CMakeLists.txt file:

# requirements.cmake

if(WIN32 AND BUILD_WITH_BAR)
  command_to_install(Bar)
endif()

# CMakeLists.txt

if(WIN32 AND BUILD_WITH_BAR)
  find_package(Bar CONFIG REQUIRED)
  target_compile_definitions(... PUBLIC "WITH_BAR")
endif()

In case when this part will change you must not to forget to modify requirements accordingly too. And real world libraries can have nontrivial chain of conditions, e.g. OpenCV components.

Stackoverflow

Pip: optional dependencies