From 37ef1295bf8885876df8de989569a2233f97583f Mon Sep 17 00:00:00 2001
From: Luke Shumaker <lukeshu@sbcglobal.net>
Date: Fri, 4 Mar 2016 13:20:55 -0500
Subject: Have the caller be responsible for setting topoutdir

---
 automake.head.mk | 11 ++++-------
 automake.txt     | 40 +++++++++++++++++++++++-----------------
 2 files changed, 27 insertions(+), 24 deletions(-)

diff --git a/automake.head.mk b/automake.head.mk
index c79da83..37d3b07 100644
--- a/automake.head.mk
+++ b/automake.head.mk
@@ -30,13 +30,10 @@ am_path = $(foreach p,$1,$(call _am_relto,$p))
 all: build
 .PHONY: all
 
-## Set topoutdir, outdir, and srcdir (assumes that topsrcdir is
-## already set, and that $(topoutdir)/config.mk has been included)
-ifeq ($(topoutdir),)
-topoutdir := $(call _am_path,$(dir $(lastword $(filter %/config.mk config.mk,$(MAKEFILE_LIST)))))
-endif
-   outdir := $(call _am_path,$(dir $(lastword $(filter-out %.mk,$(MAKEFILE_LIST)))))
-   srcdir := $(call _am_path,$(topsrcdir)/$(call _am_relto,$(topoutdir),$(outdir)))
+## Set outdir and srcdir (assumes that topoutdir and topsrcdir are
+## already set)
+outdir := $(call _am_path,$(dir $(lastword $(filter-out %.mk,$(MAKEFILE_LIST)))))
+srcdir := $(call _am_path,$(topsrcdir)/$(call _am_relto,$(topoutdir),$(outdir)))
 
 _am_included_makefiles := $(_am_included_makefiles) $(call _am_path,$(outdir)/Makefile)
 
diff --git a/automake.txt b/automake.txt
index c9834d3..935af5f 100644
--- a/automake.txt
+++ b/automake.txt
@@ -41,25 +41,14 @@ What you have to do is:
 In each source directory, you write a `Makefile`, very similarly to if
 you were writing for plain GNU Make, with
 
-    # adjust the number of `../` segments as appropriate
-    include $(dir $(lastword $(MAKEFILE_LIST)))/../../config.mk
+    topoutdir ?= ...
+    topsrcdir ?= ...
     include $(topsrcdir)/automake.head.mk
 
     # your makefile
     
     include $(topsrcdir)/automake.tail.mk
 
-And in the top-level output directory, you write a `config.mk` with:
-
-    ifeq ($(topsrcdir),)
-    # have your ./configure script adjust topsrcdir if doing an
-    # out-of-tree build
-    topsrcdir := $(patsubst %/,%,$(dir $(lastword $(MAKEFILE_LIST))))
-
-    # your configuration
-
-    endif
-
 And in the top-level source directory, Write your own helper makefiles
 that get included:
  - `common.once.head.mk`: before parsing any of your Makefiles
@@ -145,10 +134,27 @@ between directories:
 Tips, notes
 -----------
 
-If you have a `./configure` script, don't have it modify the
-`Makefile`s; have everything you need modified be in
-`$(topoutdir)/config.mk` and have it generate that; then have it copy
-(or (sym?)link?) every `$(srcdir)/Makefile` into `$(outdir)/Makefile`.
+I like to have the first (non-comment) line in a Makefile be:
+
+    include $(dir $(lastword $(MAKEFILE_LIST)))/../../config.mk
+
+(adjusting the number of `../` sequences as nescessary).  Then, my
+(user-editable) `config.mk` is of the form:
+
+    ifeq ($(topsrcdir),)
+    topoutdir := $(patsubst %/,%,$(dir $(lastword $(MAKEFILE_LIST))))
+    topsrcdir := $(topoutdir)
+
+    # your configuration
+
+    endif
+
+If the package has a `./configure` script, then I have it modifiy
+topsrcdir as necessary, as well as modifying whatever other parts of
+the configuration.  All of the configuration lives in `config.mk`;
+`./configure` doesn't modify any `Makefile`s, it just generates
+`config.mk`, and copies (or (sym?)link?) every `$(srcdir)/Makefile` to
+`$(outdir)/Makefile`.
 
 ----
 Copyright (C) 2016  Luke Shumaker
-- 
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