From dadaace394f1e5ffe1658f55c9926a8b3fc4434f Mon Sep 17 00:00:00 2001
From: Leandro Lanzieri <leandro.lanzieri@haw-hamburg.de>
Date: Tue, 30 Nov 2021 12:24:43 +0100
Subject: [PATCH] sys/log: check that one and only one backend

---
 sys/log/Makefile.include | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/sys/log/Makefile.include b/sys/log/Makefile.include
index 530c972f11..b9d4614145 100644
--- a/sys/log/Makefile.include
+++ b/sys/log/Makefile.include
@@ -1,3 +1,15 @@
+# check that one, and only one log backend is being used
+USED_LOG_BACKENDS := $(sort $(filter log_%,$(USEMODULE)))
+
+ifeq (0,$(words $(USED_LOG_BACKENDS)))
+  $(error The log module is being used but no backend is provided.)
+else ifeq (1,$(words $(USED_LOG_BACKENDS)))
+  # only one backend is provided, this is correct
+else
+  $(info Only one log backend can be used at a time.)
+  $(error Currently selecting: $(USED_LOG_BACKENDS))
+endif
+
 ifneq (,$(filter log_printfnoformat,$(USEMODULE)))
   USEMODULE_INCLUDES += $(RIOTBASE)/sys/log/log_printfnoformat
 endif