View source for User:JoeyArmstrong/makefiles/makemakefile

= post #1 =

== Build system tools: make-makefile ==

The build process consists of several steps, one of which is the dynamic generation of makefiles - the creation of recipes that control how and when elements of firefox and friends are gnerated.  The tool currently used for generation is make-makefile, a utility written way back in the days of Netscape (circa 1999).  Intent for this post and a few more that will follow will be to document the tool and usage.

== Scripts and Config ==
* build/autoconf/make-makefile
* build/autoconf/makemakefile.pm
* build/autoconf/make-makefile.excl

make-makefile will be automatically invoked while building whenever a Makefile does not exist beneath the object directory or a template (Makefile.in) is newer than a previously generated Makefile.


<hr>

= Post #2 =
<pre>
The make-makefile tool is normally invoked during recursive make traversal, indirectly launched by make -f client.mk calls.
Whenever a non-existent Makefile is detected or when a Makefile.in source template is newer than a generated file, make-makefile will be invoked to create/re-generate the target Makefile.

When launched make-makefile will determine a few path values:
     source: ${src}Makefile.in - source template for makefile generation
  generated: ${obj}/Makefile   - generated makefile with expanded paths and variables
      depth:                   - path from file to top directory (~relpath)

The tool currently expects to be launched from beneath the object directory:
  o make-makefile will be invoked from a subdirectory of $OBJ
  o command line arguments -t ${topsrcdir} -d ${depth} are passed (~config/rules.mk)
    - $depth for relative path construction
    - $topsrcdir specifies root of the source tree
  o path to source template Makefile.in will be determined
  o $DEPTH from subdirectory to ${OBJ} will be determined and the value
    will later be used to derive paths for variable expansion in the makefile.
  o Read template Makefile.in from the source directory and perform variable subst.
  o For unknown variables source the config.status file to obtain values.
  o Generate/write Makefile in a corresponding subdirectory beneath ${OBJ}.

Path to the build directory root can be determined in a few different ways:
  o from command line argument --depth
  o parse the contents of Makefile/Makefile.in and extract a 'DEPTH=' string.
  o If Makefile/Makefile.in exists in a parent directory the file can be used
    as a base for determining DEPTH for the current makefile.

Variables:
  o Makefile templates can be parameterized by variables - @{var_name}@.
    Most Makefile.in templates should have an init section similar to this:

  DEPTH		= ..
  topsrcdir	= @top_srcdir@
  srcdir	= @srcdir@
  VPATH		= @srcdir@

  include $(DEPTH)/config/autoconf.mk

  top_srcdir, srcdir and a few others are defined internally by make-makefile.
  Additional values { anything defined by configure } can also be referenced
  as an @var@ expandable value in the makefile.

Extra Configuration:
  o build/autoconf/make-makefile.excl
    Exclusion list that can be used to inhibit generation of certain makefiles.
    If makefiles are being deprecated or have broken building presence on this
    list will inhibit their generation.

Enhancements {{bug|687511}} to support container makefile prototyping.
  o Remove restriction requiring that the tool can be used from the $OBJ directory.
  o Arguments added to allow passing in the path to Makefile and Makefile.in
  o When both file paths are available logic can be simplified.  Relative path,
    depth, $topsrcdir values can be set by derivation rather than searching.
</pre>