This file was imported from glibx and uses __USE_GNU as defined by glibc(s features.h. Our implementation of features.h is simpler, just defining _DEFAULT_SOURCE directly and that's what we use in other headers. As a result, using GNU extensions to regex.h required defining __USE_GNU directly in applications (for example in TraX). Fixes #11818 Change-Id: I11e4cf2e88c330cf58083852c4b33aedb8a3a9ea Reviewed-on: https://review.haiku-os.org/c/haiku/+/7238 Reviewed-by: waddlesplash <[email protected]> Tested-by: Commit checker robot <[email protected]>