+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])
+