Without _GNU_SOURCE defined this file fails to compile with the
following error:
$ gcc manual/examples/twalk.c
manual/examples/twalk.c: In function ‘twalk’:
manual/examples/twalk.c:55:3: error: implicit declaration of function ‘twalk_r’; did you mean ‘twalk’? [-Wimplicit-function-declaration]
55 | twalk_r (root, twalk_with_twalk_r_action, &closure);
| ^~~~~~~
| twalk
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
along with this program; if not, see <https://www.gnu.org/licenses/>.
*/
+#define _GNU_SOURCE 1
#include <search.h>
struct twalk_with_twalk_r_closure