From aa20c416c38426e790543dca2652b083a52d8a58 Mon Sep 17 00:00:00 2001
From: Michael Stapelberg <stapelberg@users.noreply.github.com>
Date: Sat, 19 Nov 2016 14:45:22 -0800
Subject: [PATCH] configure.ac: verify macros in m4/ are being replaced (Thanks
 sur5r) (#2571)

See the comment for more details, and see the motivating blog post:
https://blogs.noname-ev.de/sur5r/index.php?/archives/7-Another-instance-of-AC_DEFINE-being-undefined.html
---
 configure.ac | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/configure.ac b/configure.ac
index 1a91b3b1..b57f9efa 100644
--- a/configure.ac
+++ b/configure.ac
@@ -15,6 +15,12 @@ AC_CONFIG_SRCDIR([libi3/ipc_recv_message.c])
 AC_CONFIG_HEADERS([config.h])
 AC_CONFIG_MACRO_DIR([m4])
 
+dnl Verify macros defined in m4/ such as AX_SANITIZERS are not present in the
+dnl output, i.e. are replaced as expected. This line results in a better error
+dnl message when using aclocal < 1.13 (which does not understand
+dnl AC_CONFIG_MACRO_DIR) without passing the -I m4 parameter.
+m4_pattern_forbid([AX_SANITIZERS])
+
 # Verify we are using GNU make because we use '%'-style pattern rules in
 # Makefile.am, which are a GNU make extension. Pull requests to replace
 # '%'-style pattern rules with a more portable alternative are welcome.