[PATCH 1/2] build: Detect guile M4 macro expansion errors

[Mathieu Lirzin]

This ensures that the absence of 'pkg-config' or 'guile' M4 macros
expansion do not pass the bootstrap step.

* configure.ac: Allow or forbid some M4 macros patterns in the generated
'configure' script.
---
 configure.ac | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/configure.ac b/configure.ac
index f92619b..d27e12e 100755
--- a/configure.ac
+++ b/configure.ac
@@ -1,7 +1,7 @@
 ## Process this file with autoconf to produce a configure script.
 #
 # Copyright © 2003, 2005, 2012, 2014 Dale Mellor <address@hidden>
-# Copyright © 2015, 2016, 2017, 2018 Mathieu Lirzin <address@hidden>
+# Copyright © 2015, 2016, 2017, 2018, 2020 Mathieu Lirzin <address@hidden>
 # Copyright © 2018 宋文武 <address@hidden>
 #
 # This file is part of GNU Mcron.
@@ -33,6 +33,13 @@ AM_SILENT_RULES([yes])               # Enables silent rules 
by default.
 
 AC_CANONICAL_HOST
 
+dnl We require pkg.m4 (from pkg-config) and guile.m4 (from Guile.)
+dnl Make sure they are available when generating the configure script.
+m4_pattern_forbid([^PKG_PROG])
+m4_pattern_forbid([^PKG_CHECK])
+m4_pattern_forbid([^GUILE_P])
+m4_pattern_allow([^GUILE_PKG_ERRORS])
+
 # Check for Guile development files.
 GUILE_PKG([3.0 2.2 2.0])
 
-- 
2.20.1