diff -r c649a735cf82 testing/support.py
--- a/testing/support.py	Thu Feb 23 05:42:01 2023 +0100
+++ b/testing/support.py	Sat May 20 21:46:56 2023 -0400
@@ -112,6 +112,7 @@
                               '-Wno-unreachable-code']
         # special things for clang
         extra_compile_args.append('-Qunused-arguments')
+        extra_compile_args.append('-Wno-null-pointer-subtraction')
     else:
         # assume a standard gcc
         extra_compile_args = ['-Werror', '-Wall', '-Wextra', '-Wconversion',