Masahiro Yamada [off-list ref] writes:

Without this patch, there are some functions that start with double
underscores.

For example,

  __expr_eliminate_eq() in scripts/kconfig/expr.c
  __expand_string()  in scripts/kconfig/preprocess.c

Are they problematic as well?

Yes, they could be potentially problematic. Identifiers that start
with double underscores or with a single underscore followed by an
uppercase letter are reserved for use by the C implementation (for
example, as a pre-defined macro).