diff options
Diffstat (limited to 'src/Makefile.in')
-rw-r--r-- | src/Makefile.in | 40 |
1 files changed, 14 insertions, 26 deletions
diff --git a/src/Makefile.in b/src/Makefile.in index 5bed189f16..748f38e55b 100644 --- a/src/Makefile.in +++ b/src/Makefile.in @@ -1,7 +1,7 @@ ### @configure_input@ -# Copyright (C) 1985, 1987-1988, 1993-1995, 1999-2014 Free Software -# Foundation, Inc. +# Copyright (C) 1985, 1987-1988, 1993-1995, 1999-2014 +# Free Software Foundation, Inc. # This file is part of GNU Emacs. @@ -594,40 +594,28 @@ tags: TAGS ../lisp/TAGS $(lwlibdir)/TAGS ## such as loaddefs.el or *.elc can typically be produced by any old ## Emacs executable, so we would like to avoid rebuilding them whenever ## we build a new Emacs executable. +## +## (In other words, changing a single file src/foo.c would force +## dumping a new bootstrap-emacs, then re-byte-compiling all preloaded +## elisp files, and only then dump the actual src/emacs, which is not +## wrong, but is overkill in 99.99% of the cases.) +## ## To solve the circularity, we use 2 different Emacs executables, ## "emacs" is the main target and "bootstrap-emacs" is the one used ## to build the *.elc and loaddefs.el files. -## To solve the freshness issue, we used to use a third file "witness-emacs" -## which was used to witness the fact that there is a bootstrap-emacs -## executable, and then have dependencies on witness-emacs rather than -## bootstrap-emacs, but that lead to problems in parallel builds (because -## witness-emacs needed to be free from dependencies (to avoid rebuilding -## it), so it was compiled in parallel, leading typically to having 2 -## processes dumping bootstrap-emacs at the same time). -## So instead, we replace the witness-emacs dependencies by conditional -## bootstrap-dependencies (via $(BOOTSTRAPEMACS)). Of course, since we do -## not want to rely on GNU Make features, we have to rely on an external -## script to do the conditional part of the dependency -## (i.e. see the $(SUBDIR) rule ../Makefile.in). - -.SUFFIXES: .elc .el - -## These suffix rules do not allow additional dependencies, sadly, so -## instead of adding a $(BOOTSTRAPEMACS) dependency here, we add it -## separately below. -## With GNU Make, we would just say "%.el : %.elc $(BOOTSTRAPEMACS)" -.el.elc: - @$(MAKE) -C ../lisp compile-onefile THEFILE=$< EMACS="$(bootstrap_exe)" +## To solve the freshness issue, in the past we tried various clever tricks, +## but now that we require GNU make, we can simply specify +## bootstrap-emacs$(EXEEXT) as an order-only prerequisite. -## Since the .el.elc rule cannot specify an extra dependency, we do it here. -$(lisp): $(BOOTSTRAPEMACS) +%.elc: %.el | bootstrap-emacs$(EXEEXT) + @$(MAKE) -C ../lisp compile-onefile THEFILE=$< EMACS="$(bootstrap_exe)" ## VCSWITNESS points to the file that holds info about the current checkout. ## We use it as a heuristic to decide when to rebuild loaddefs.el. ## If empty it is ignored; the parent makefile can set it to some other value. VCSWITNESS = -$(lispsource)/loaddefs.el: $(BOOTSTRAPEMACS) $(VCSWITNESS) +$(lispsource)/loaddefs.el: $(VCSWITNESS) | bootstrap-emacs$(EXEEXT) $(MAKE) -C ../lisp autoloads EMACS="$(bootstrap_exe)" ## Dump an Emacs executable named bootstrap-emacs containing the |