make: add initial ubsan support

Makefile.include

@@ -503,6 +503,9 @@ include $(RIOTMAKE)/toolchain/$(TOOLCHAIN).inc.mk
 # overriding the core ldscripts
 LINKFLAGS += -L$(RIOTBASE)/core/ldscripts
 
+# include undefined behaviour sanitizer (UBSAN) support
+include $(RIOTMAKE)/ubsan.inc.mk
+
 # Tell ccache to pass the original file to the compiler, instead of passing the
 # preprocessed code. Without this setting, the compilation will fail with
 # -Wimplicit-fallthrough warnings even when the fall through case is properly

makefiles/ubsan.inc.mk

@@ -0,0 +1,36 @@
+# Copyright (C) 2019 Kaspar Schleiser <kaspar@schleiser.de>
+#
+# This file contains support for UBSan, the undefined behaviour sanitizer
+# provided by gcc and clang.
+#
+# Please see doc/doxygen/src/debugging-aids.md for more info.
+
+# trap, msg_exit, msg_recover
+UBSAN_MODE ?= msg_exit
+
+CFLAGS_UBSAN = -fsanitize=undefined
+
+ifeq (gnu,$(TOOLCHAIN))
+  ifeq (native,$(BOARD))
+    ifneq (,$(filter msg_%,$(UBSAN_MODE)))
+      LINKFLAGS_UBSAN += -lubsan
+      ifneq (msg_recover,$(UBSAN_MODE))
+        CFLAGS_UBSAN += -fno-sanitize-recover=undefined
+      endif
+    else
+      CFLAGS_UBSAN += -fsanitize-undefined-trap-on-error
+    endif
+  else
+    # on real hardware, there's currently no runtime support.
+    # so just crash when undefined behaviour is triggered.
+    CFLAGS_UBSAN += -fsanitize-undefined-trap-on-error
+  endif
+else
+  # libubsan doesn't link properly when using clang.
+  # thus when using llvm as toolchain, always generate traps.
+  CFLAGS_UBSAN += -fsanitize-trap=undefined
+endif
+
+all-ubsan: CFLAGS += $(CFLAGS_UBSAN)
+all-ubsan: LINKFLAGS += $(LINKFLAGS_UBSAN)
+all-ubsan: all