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Use files

Intro

Use files specify the C and ooc dependencies of a library, along with some basic info like its name, description.

They are useful for package managers (see sam), but also for the rock compile, to import required ooc libraries, and to know which flags and libraries to pass to the C compiler.

A few well-written .use files make using libraries very easy, without having to worry about writing a Makefile of some sort, and it makes compiling programs on various platforms a no-brainer.

.use files are generally located at the root of an ooc app or library.

For a language binding, the tree structure is usually:

ooc-gtk
  README.md
  gtk.use
  source
    gtk
  samples

For a pure ooc library or application, the tree structure is usually:

deadlogger
  README.md
  deadlogger.use
  source
    deadlogger
  samples

Libs search path

Using a third-party ooc library is as easy as doing use library in an .ooc file

When doing so, the ooc compiler will look for a library.use file in your lib folders.

The $OOC_LIBS environment variable defines the lib folders, separated by : on *nix, and ';' on Windows.

A simple setup is to have all your ooc libraries sitting in the same folder, for example $HOME/Dev/, with the following structure:

someproject
  someproject.use
ooc-gtk
  gtk.use
rock
  rock.use
  sdk.use
  math.use
  pcre.use

Note that the standard ooc sdk is a library like any other - it has a .use file with standard directives as defined below.

Syntax

The file is composed of key-value pairs, formatted like this:

Key1: Value1
Key2: Value2

Whitespace around the colon : doesn't matter. For keys that accept multiple directives like Libs or IncludePaths, values should be separated by commas (and whitespace is accepted).

For example, this is wrong:

Libs: -lGLU -lGL

And this is right:

Libs: -lGLU, -lGL

Versioning

A use file might be versioned using version blocks, however, only some directives are valid in a version block.

Here's an example:

Name: SDL 2.0 OpenGL support

version (linux) {
  Libs: -lGL
}

version (apple) {
  Frameworks: Carbon, OpenGL
}

Version blocks have the same syntax as in .ooc files. For more details, see the version chapter.

Top-level directives

Those directives cannot be versioned and must appear at the top level of a use file.

# Short description
Name: llama

# Longer description
Description: A lib to deal with llamas

# The version of the library
Version: 0.1.3

# Modules that are automatically imported when 'use'-ing this library
Imports: llama/beast, llama/human

# For programs, the main ooc file to compile when rock is called without arguments
Main: llama/program

# This will be added to the list of folders the ooc compiler looks for .ooc files
SourcePath: source

# Dependencies - the 'use' of .use files
Requires: spit

Basic directives

# gcc's -I
IncludePaths: /some/weird/place/include

# will be included in all files using this .use file
Includes: someheader.h, someother.h

# gcc's -L
LibPaths: /some/weird/place/include

# will be linked with the final executable
Libs: -lsomething, -lotherthing

# additional .c files to compile and link into the library/executable
Additionals: source/somefile.c

pkg-config packages

For many packages, there is already a pkg-config .pc file with the information needed to make it compile right. What's more, that file is often customized depending on what system you install the library on, which makes version blocks unnecessary.

Whenever a package has a pkg-config file, it is imperative to use Pkgs instead of specifying manually IncludePaths, Includes, LibPaths, and Libs.

For example, the cairo.use file would probably contain:

Pkgs: cairo

pkg-config-like utilities

Sometimes, libraries ship with pkg-config-like utilities. imlib2-config, sdl2-config, llvm-config. Those are often used similarly as pkg-config, except without specifying a package.

When this is the case, a simple form of CustomPkg does the trick:

CustomPkg: sdl2-config

However, others have more complex options. For those, the full power of CustomPkg is required, with 4 arguments:

  • The name of the utility to run
  • A list of arguments space-separated, always passed to the utility
  • Equivalent to pkg-config --cflags option
  • Equivalent to pkg-config --libs option

For llvm-config, this boils down to:

CustomPkg: llvm-config, core executionengine jit, --cflags, --libs --ldflags

Custom linkers

Some C++ libraries will required a C++ linker in order to work. LLVM does.

Hence, the Linker directive:

Linker: g++

Otherwise, the ooc compiler uses the same linker as your specified C compiler.

OSX-specific directives

OSX has some libraries packaged in frameworks instead of unix-y libs. For example, on OSX, -lGL doesn't exist. For those cases, the Frameworks directive can be used:

Frameworks: Carbon, OpenGL

This directive has no effect on other platforms, even outside version blocks.

Android-specific directives

The android build process has some intricacies, which is why .use files can contain android-specific directives:

AndroidLibs: SDL2
AndroidIncludes: ../SDL/

These really depend on the setup of your android project but it makes sense.

AndroidLibs are mk dependencies that need to be built, and AndroidIncludes are include paths, relative to the subfolder of your app/library.

These directives have no effect on other platforms, even outside version blocks.

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