From: Andre Noll <maan@tuebingen.mpg.de>
Date: Sun, 25 Apr 2021 22:04:05 +0000 (+0200)
Subject: build: Bail out early if m4 or lex don't exist.
X-Git-Tag: v1.0.4~5^2~3
X-Git-Url: http://git.tue.mpg.de/?a=commitdiff_plain;h=7623e601612eb36cf86511b40fef3f5a20e8b834;p=lopsub.git

build: Bail out early if m4 or lex don't exist.

This gives a decent error message on the attempt to run make(1) on a
system where one or both of these essential programs are not installed.

A previous version of the patch used .SHELLSTATUS instead of the
dummy variable, but this did not work with make-4.1 which ships
with Ubuntu-18.04.

Suggested-by: Alex Gietz <oss@mcdinner.de>
---

diff --git a/Makefile b/Makefile
index 200a7c0..c0057a3 100644
--- a/Makefile
+++ b/Makefile
@@ -21,6 +21,15 @@ INSTALL := install
 GZIP := gzip -fn9
 ZCAT := zcat
 
+dummy != $(M4) /dev/null || printf 'failed'
+ifeq ($(dummy), failed)
+$(error m4 is required to build this package)
+endif
+dummy != printf '%%%%\n' | $(LEX) -o /dev/null || printf 'failed'
+ifeq ($(dummy), failed)
+$(error (f)lex is required to build this package)
+endif
+
 DATE_FMT := +%B %Y
 # To get a reproducible build, we use $(SOURCE_DATE_EPOCH) instead of the
 # current time if this variable is set.