// SPDX-License-Identifier: GPL-2.0
  #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, [buf], %zd)=%d", errnum, buflen, err);
  	return buf;
  }