ocaml/ocamlbuild/ocamlbuild-presentation.rslide

documentclass :beamer, :t, :compress, :red
usepackage    :inputenc, :utf8

words "**OCaml**", "**ocamlbuild**", "_Makefile_"

title     "ocamlbuild, a tool for automatic compilation of OCaml projects"
authors   "Berke Durak", "Nicolas Pouillard"
institute do
  > @@Berke.Durak@inria.fr@@
  hfill
  > @@Nicolas.Pouillard@inria.fr@@
end

usetheme      :JuanLesPins
usefonttheme  :serif
beamer_header '\setbeamercolor*{titlelike}{parent=structure}'
at_begin_section do
  slide "Outline" do
    tableofcontents 'sectionstyle=show/shaded',
                    'subsectionstyle=show/shaded/hide'
  end
end
beamer_footline 50, 0

extend do
  module ::Rslide::Tags
    class CodeCaml < Code
    end
    class CodeTags < Code
    end
  end
end

maketitle

h1 "Introduction"

slide "Why such a tool?", '<+->' do
  * To make our OCaml life easier
  * To stop writing poor MakefileS
  * To have a tool that Just works™
end

slide "What does ocamlbuild handle?", '<+->' do

  box "Regular OCaml projects of arbitrary size" do
    > Trivially handled using the command line options.
  end

  box "Mostly regular OCaml projects with common exceptions" do
    > Requires writing one tag file (__tags_) that declares those exceptions.
  end

  box "Almost any project" do
    > Accomplished by writing an ocamlbuild plugin.
  end

end

slide "What does ocamlbuild provide?" do
  list do
    overlay 1,2 do
      * Automated whole-project compilation
      * Minimal recompilation
      * Lots of useful targets (doc, debugging, profiling...)
      * Supports multiple build directories
      * Automatic and safe cleaning
      * A source directory uncluttered by object files
      * A portable tool shipped with OCaml
    end
    overlay 2 do
      * Saves time and money!
    end
  end
end

h1 "Regular OCaml projects"

slide "What's a regular OCaml project?" do
  box "It's a project that needs no exceptions from the standard rules:" do
    * Has compilation units (_ml_ and _mli_ files)
    * May have parsers and lexers (_mly_ and _mll_ files)
    * May use packages, libraries and toplevels (_ml{pack,lib,top}_)
    * May link with external libraries
    * Has one main OCaml unit from which these units are reachable
  end
end

slide "How difficult is it to compile regular projects by hand?" do
  box "OCaml has subtle compilation rules" do
    * Interfaces (_.mli_) can be absent, yet buildable (_.mly_)
    * Native and bytecode suffixes and settings differ
    * Native packages are difficult to do (_-for-pack_)
    * Linkage order must be correctly computed
    * Include directories must be ordered
    * _ocamldep_ gives partial information (too conservative)
  end
end

slide "How does ocamlbuild manage all that?" do
  > It has a lot of hand-crafted Ocaml-specific compilation logic!
  box "A dynamic exploration approach", '<2>' do
    * Start from the given targets
    * Attempt to discover dependencies using _ocamldep_
    * _ocamldep_ cannot always be trusted: backtrack if necessary
    * Launch compilations and discover more dependencies
  end
end

slide "Demo..." do
  box "Many projects can be compiled with a single command:" do
    * Menhir: _ocamlbuild -lib unix back.native_
    * Hevea: _ocamlbuild latexmain.native_
    * Ergo: _ocamlbuild main.native_
    * Ocamlgraph: _ocamlbuild -cflags -for-pack,Ocamlgraph demo.native_
    * ...
  end
  box "To be fair..." do
    > Some of these projects require that a _version.ml_
      or _stdlib.ml_ file be generated beforehand.
  end
end

h1 "Dealing with exceptions to standard rules"

slide "What's an exception?" do
  box "Files that need specific flags" do
    * Warnings to be enabled or disabled
    * Debugging (_-g_), profiling (_-p_), type annotation,
      recursive types, _-linkall_, _-thread_, _-custom_...
  end
  list do
    * Units that need external C libraries
    * Binaries that need external OCaml libraries
    * Directories that must be included or excluded
    * Dependencies that cannot be discovered
  end
end

slide "_Make_ and exceptions" do
  * The _make_ tool can't handle exceptions very well
  * Needs exceptions to be encoded as specific rules
  * This generally makes rules and exceptions tightly bound by variables
  * This creates non-modular makefiles that don't *scale*
end

slide "The tags, our way to specify exceptions", 'fragile=singleslide' do
  list do
    * The _tags file is made of lines
    * Each line is made of a pattern and a list of signed tags
    * A line adds or removes tags from matching files
    * Patterns are boolean combinations of shell-like globbing expressions
  end
  code_tags do
    : "funny.ml":           rectypes
      <**/*.ml*>:           warn_A, warn_error_A, debug, dtypes
      <**/*.cmx>:           inline(9)
      "foo.ml" or "bar.ml": warn_v, warn_error_v
      "vendor.ml":          -warn_A, -warn_error_A
      <main.{byte,native}>: use_unix
      "main.byte":          use_dynlink, linkall
      "test":               not_hygienic
      <satsolver.cm[io]>:   precious
  end
end

slide "How tags and rules give commands", 'fragile=singleslide' do
  box "Files are tagged using tagging rules" do
    code_tags do
      : "foo/bar.ml": rectypes
    end
  end
  box "Rules then produce commands with *tagged holes*" do
    code_caml do
      : let tagged_hole =
          tags_for(ml)++"ocaml"++"compile"++"byte" in
        Cmd(S[A"ocamlc";A"-c";T tagged_hole;P ml;A"-o";P cmo])
    end
  end
  box "These holes are filled by command fragments (such as flags)" do
    code_caml do
      : flag ["ocaml"; "compile"; "byte"; "rectypes"]
             (A"-rectypes")
    end
  end
end

slide "Tags and dependencies", 'fragile=singleslide' do
  box "One can define dependencies triggered by combinations of tags" do
    code_caml do
      : dep ["ocaml"; "link"; "byte"; "program"; "plugin:foo"]
            ["plugin/pluginlib.cma"; "plugin/plugin_foo.cmo"]
    end
  end
  box "By tagging files we make things happen" do
    code_tags do
      : "test.byte": plugin:foo
    end
  end
end

h1 "Writing an ocamlbuild plugin"

slide "Not a specific language, but plain OCaml code" do
  * Plugins are compiled on the fly
  * Dynamic configuration is feasible
  box "With a plugin one can:" do
    * Extend rules (add new ones, override old ones)
    * Add flags and dependencies based on tags
    * Tag files
    * Change options
    * Define the directory structure precisely
    * Help _ocamldep_
    * Specify external libraries
  end
end

slide "A plugin example" do
  > Let's read it in live...
end

# slide "ocamlbuild scales" do
#   > Indeed ocamlbuild is used as an experimental replacement in OCaml itself.
# end

h1 "General features"

slide "Parallel execution where applicable" do
  * You select the maximum number of jobs (_-j N_)
  * Rules know how to ask for parallel targets
  * The system keeps things scheduled correctly
  * Example: Separate compilation of byte code
  * (Optimal scheduling would require a static graph)
end

slide "A status bar for your visual comfort" do
  * Compilation tools echo commands and their output
  * This creates a long and boring output that scrolls too fast
  * Here you can keep an eye on what is going on!
  * It succinctly displays time, number of targets, and tags
  * Command outputs are correctly multiplexed
  * A trace of the commands executed is kept in a log file
  * This log file can be used as the basis of a shell script
  example do
    invisible_join do
      count = 0
      mod = 1
      File.read("manual/trace.out").each do |line|
        count += 1
        next if count % mod != 0
        line.gsub!("\\", "|")
        line.latex_encode!
        line.gsub!(/( +)/) { "\\hspace{#{0.49 * $1.size}em}" }
        line.chomp!
        s = "\\only<#{count / mod}>{\\tt #{line}}%\n"
        verbatim_text s
      end
    end
  end
end

slide "Hygiene and sterilization" do
  * ocamlbuild has a Hygiene Squad (HS) that checks your source tree for cleanliness
  box "It has preconceived but useful cleanliness notions", '<1->' do
    * Files dirty by default: _.cmi_, _.cmo_, _.cma_, _.cmx_...
    * _ocamllex_/_ocamlyacc_ files: _.ml_ *if* _.mll_, _.ml_&_.mli_ *if* _.mly_...
  end
  box "If unsatisfied, the HS produces a sterilization script", '<2->' do
    * Read it carefully (or work with versioning)
    * Run at your own risks
  end
  box "HS can be told of exceptions", '<3->' do
    > Files or directories tagged as __not_hygienic__ or _precious_.
  end
end

slide "Some supported tools" do
  box "_Menhir_ as an _ocamlyacc_ replacement", '<1->' do
    * Enabled with the __use_menhir__ global tag or the __-use-menhir__ option
    * Handles implicit dependencies using _--infer_
  end
  box "_Ocamldoc_ to build your doc", '<2->' do
    * Separated construction using (_-dump_/_-load_)
    * Handles ??HTML??, ??LaTeX??, ??Man??, ??Dot??, ??TeXi??
  end
  # box "_ocamlmklib_, _ocamlmktop_" do
  #   > Basic support using _.mllib_ and _.mltop_ files
  # end
  box "_Camlp4_ aware", '<3->' do
    * Tags allow to setup any installed _Camlp4_ preprocessor
    * Fine grained dependencies help a lot...
  end
end

h1 "Conclusion"

slide "Resume" do
  box "ocamlbuild can be used in three ways:", '<1->' do
    * With only command-line options for fully regular projects
    * With the __tags_ file for intermediate projects
    * With a plugin for the most complex projects
  end
  box "ocamlbuild saves your time by:", '<2->' do
    * Building your project gently
    * Compiling only as necessary
    * Running commands in parallel
    * Keeping your house clean
    * Letting you concentrate on your code!
  end
end

slide "Acknowledgments" do
  box "For enlightening discussions about OCaml internals:", '<1->' do
    * Xavier Leroy
    * Damien Doligez
  end
  box "For his insights about OCaml dependencies:", '<2->' do
    * Alain Frisch
  end
  box "For letting this happen:", '<3->' do
    * Michel Mauny
  end
end

slide "Conclusion", '<+->' do
  * ocamlbuild is not perfect but already damn useful
  * It will be in 3.10, so feel free to use it
  * Try it now! It's in the CVS!
end