#undef _GNU_SOURCE#include <string.h>#include <stdio.h>#include <linux/string.h> /* * The tools so far have been using the strerror_r() GNU variant, that returns * a string, be it the buffer passed or something else. * * But that, besides being tricky in cases where we expect that the function * using strerror_r() returns the error formatted in a provided buffer (we have * to check if it returned something else and copy that instead), breaks the * build on systems not using glibc, like Alpine Linux, where musl libc is * used. * * So, introduce yet another wrapper, str_error_r(), that has the GNU * interface, but uses the portable XSI variant of strerror_r(), so that users * rest asured that the provided buffer is used and it is what is returned. */char *str_error_r(int errnum, char *buf, size_t buflen){	int err = strerror_r(errnum, buf, buflen);	if (err)		snprintf(buf, buflen, "INTERNAL ERROR: strerror_r(%d, %p, %zd)=%d", errnum, buf, buflen, err);	return buf;}