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Compiling with GNU make

Using GNU make with OCamlMakefile

OCamlMakefile is a generic Makefile that greatly facilitates the process of compiling complex OCaml projects.

For a basic OCaml program or library that doesn't use any library besides the standard library, just copy OCamlMakefile to the current directory and create the following Makefile:

RESULT = myprogram
SOURCES = \
  mymodule1.mli mymodule1.ml \
  myparser.mli myparser.mly mylexer.mll mymodule2.ml \
  mymainprogram.ml
  
OCAMLMAKEFILE = OCamlMakefile
include $(OCAMLMAKEFILE)

This is already a fairly complex program which has 5 compilation units and uses ocamlyacc and ocamllex. Only the source files must be given, except for the .mli files that are produced by ocamlyacc, myparser.mli in the example.

The included OCamlMakefile provides a variety of targets. For details please refer to the documentation of OCamlMakefile, but here are the main ones:

nc     make a native code executable
bc     make a bytecode executable
ncl    make a native code library
bcl    make a bytecode library
libinstall    install library with ocamlfind
libuninstall  uninstall library with ocamlfind
top    make a custom interactive toplevel from all your modules
clean  remove everything that matches one of the files that could have been
       automatically created by OCamlMakefile

OCamlMakefile + libraries + Camlp4 parsing

The recommended tool for installing OCaml libraries is Findlib (ocamlfind command) since it knows where packages are installed, loads their dependencies and knows which file should be used in a given situation.

If you do not use Findlib, loading a regular runtime library can be done by setting the LIBS and INCDIRS variable. LIBS is the list of the name of the library files (xxx.cma or xxx.cmxa) without the .cma or .cmxa extension:

LIBS = str unix

If you use non-standard libraries that are not installed in the same directory as the standard library, the INCDIRS variable must contain the list of these directories:

INCDIRS = /path/to/somelibdirectory/

Usually this requires some preliminary configuration as it is traditionally performed with a configure script since the path can vary from one installation to another.

OK, but we prefer libraries that are installed with ocamlfind. To use them with OCamlMakefile, the PACKS variable must be set:

PACKS = netstring num

Note that libraries that not part of the standard library but are shipped with any standard OCaml installation such as unix, str or bigarray are automatically considered as Findlib packages. Any package which is required by a given package (e.g. netstring requires unix and pcre) is automatically loaded.

Summary

You need:

  • GNU make
  • OCamlMakefile (copied to the project's main directory)
  • Findlib (ocamlfind)
  • write a small Makefile according to the template below
  • add a constant magic line at the beginning of your source files

Full example using ocamllex and the unix and micmatch_pcre libraries. The Makefile file would be:

RESULT = myprogram
SOURCES = mymodule1.mll mymodule2.mli mymodule2.ml mymainmodule.ml
PACKS = unix micmatch_pcre
CREATE_LIB = yes # ???
OCAMLMAKEFILE = OCamlMakefile
include $(OCAMLMAKEFILE)