Derive configs

bake supports deriving configs, which allows you to put repetetive settings in a base config.

Deriving a config

Derving a config in bake is pretty straight forward, and looks like this:

ExecutableConfig A
LibraryConfig    B, extends: A
CustomConfig     C, extends: B
ExecutableConfig D, extends: C

Note

The config type of the parent config does not matter, but only settings which are valid in BOTH configs will be inherited. In the example above D gets the dependencies from A, because “Dependency” is valid in all configs, but D does not get the “Files” from A and B, because “Files” is not valid in CustomConfig.

Inheritance implications

In general it is very easy.

  • Elements which can exist more than once (e.g. “Files”), are simply concatenated. First the parent elements, then the client elements.
  • Elements which can exist only once:
    • if it exists in EITHER child OR parent, use this one
    • is it exists in BOTH, attributes are merged (child attributes have high priority) and sub elements are inherited recursively

The following example

ExecutableConfig A {
  Files "x.cpp"
  Files "y.cpp"
  ArtifactName "z.exe"
  DefaultToolchain GCC {
    Linker {
      Flags "-O3"
    }
  }
}
ExecutableConfig B, extends: A {
  Files "z.cpp"
  IncludeDir "inc"
  ArtifactName "a.exe"
  DefaultToolchain Diab {
    Compiler CPP {
      Define "TEST"
    }
  }
}

results implicitly in:

ExecutableConfig B {
  Files "x.cpp"
  Files "y.cpp"
  Files "z.cpp"
  IncludeDir "inc"
  ArtifactName "a.exe"
  DefaultToolchain Diab {
    Compiler CPP {
      Define "TEST"
    }
    Linker {
      Flags "-O3"
    }
  }
}

Multiple inheritance

It is possible to derive from several projects:

ExecutableConfig A
LibraryConfig    B
ExecutableConfig C, extends: "A, B"

“extends” defines a comma separated list. The merge will be performed with all parent configs.