From 0b3959406003cb61c9d10e2f1d45c755ec700392 Mon Sep 17 00:00:00 2001
From: Luke Shumaker <lukeshu@sbcglobal.net>
Date: Sun, 29 May 2016 18:39:41 -0400
Subject: add checks that top{src,out}dir are set

---
 build-aux/Makefile.head.mk | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/build-aux/Makefile.head.mk b/build-aux/Makefile.head.mk
index e5ef379..c680f41 100644
--- a/build-aux/Makefile.head.mk
+++ b/build-aux/Makefile.head.mk
@@ -16,6 +16,13 @@
 # This bit only gets evaluated once, at the very beginning
 ifeq ($(_at.NO_ONCE),)
 
+ifeq ($(topsrcdir),)
+$(error topsrcdir must be set before including Makefile.head.mk)
+endif
+ifeq ($(topoutdir),)
+$(error topoutdir must be set before including Makefile.head.mk)
+endif
+
 _at.noslash = $(patsubst %/.,%,$(patsubst %/,%,$1))
 # These are all $(call _at.func,parent,child)
 #_at.relto = $(if $2,$(shell realpath -sm --relative-to='$1' $2))
-- 
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