diff --git a/debug/Makefile b/debug/Makefile
index 880477632e..96029f32ee 100644
--- a/debug/Makefile
+++ b/debug/Makefile
@@ -132,6 +132,12 @@ define cflags-lfs
 CFLAGS-tst-fortify-$(1)-lfs-$(2).$(1) += -D_FILE_OFFSET_BITS=64
 endef
 
+define cflags-nongnu
+CFLAGS-tst-fortify-$(1)-nongnu-$(2).$(1) += -D_LARGEFILE64_SOURCE=1
+endef
+
+src-chk-nongnu = \#undef _GNU_SOURCE
+
 # We know these tests have problems with format strings, this is what
 # we are testing.  Disable that warning.  They are also testing
 # deprecated functions (notably gets) so disable that warning as well.
@@ -145,13 +151,13 @@ CFLAGS-tst-fortify-$(1)-$(2)-$(3).$(1) += -D_FORTIFY_SOURCE=$(3) -Wno-format \
 $(eval $(call cflags-$(2),$(1),$(3)))
 $(objpfx)tst-fortify-$(1)-$(2)-$(3).$(1): tst-fortify.c Makefile
 	( echo "/* Autogenerated from Makefile.  */"; \
-	  echo ""; \
+	  echo "$(src-chk-$(2))"; \
 	  echo "#include \"tst-fortify.c\"" ) > $$@.tmp
 	mv $$@.tmp $$@
 endef
 
 chk-extensions = c cc
-chk-types = default lfs
+chk-types = default lfs nongnu
 chk-levels = 1 2 3
 
 $(foreach e,$(chk-extensions), \
diff --git a/debug/tst-fortify.c b/debug/tst-fortify.c
index 9288610fe6..d65a2fe6e1 100644
--- a/debug/tst-fortify.c
+++ b/debug/tst-fortify.c
@@ -1,4 +1,5 @@
 /* Copyright (C) 2004-2022 Free Software Foundation, Inc.
+   Copyright The GNU Toolchain Authors.
    This file is part of the GNU C Library.
 
    The GNU C Library is free software; you can redistribute it and/or
@@ -36,6 +37,17 @@
 #include <sys/socket.h>
 #include <sys/un.h>
 
+#ifndef _GNU_SOURCE
+# define MEMPCPY memcpy
+# define WMEMPCPY wmemcpy
+# define MEMPCPY_RET(x) 0
+# define WMEMPCPY_RET(x) 0
+#else
+# define MEMPCPY mempcpy
+# define WMEMPCPY wmempcpy
+# define MEMPCPY_RET(x) __builtin_strlen (x)
+# define WMEMPCPY_RET(x) wcslen (x)
+#endif
 
 #define obstack_chunk_alloc malloc
 #define obstack_chunk_free free
@@ -162,7 +174,7 @@ do_test (void)
   if (memcmp (buf, "aabcdefghi", 10))
     FAIL ();
 
-  if (mempcpy (buf + 5, "abcde", 5) != buf + 10
+  if (MEMPCPY (buf + 5, "abcde", 5) != buf + 5 + MEMPCPY_RET ("abcde")
       || memcmp (buf, "aabcdabcde", 10))
     FAIL ();
 
@@ -207,7 +219,7 @@ do_test (void)
   if (memcmp (buf, "aabcdefghi", 10))
     FAIL ();
 
-  if (mempcpy (buf + 5, "abcde", l0 + 5) != buf + 10
+  if (MEMPCPY (buf + 5, "abcde", l0 + 5) != buf + 5 + MEMPCPY_RET ("abcde")
       || memcmp (buf, "aabcdabcde", 10))
     FAIL ();
 
@@ -266,7 +278,8 @@ do_test (void)
   if (memcmp (a.buf1, "aabcdefghi", 10))
     FAIL ();
 
-  if (mempcpy (a.buf1 + 5, "abcde", l0 + 5) != a.buf1 + 10
+  if (MEMPCPY (a.buf1 + 5, "abcde", l0 + 5)
+      != a.buf1 + 5 + MEMPCPY_RET ("abcde")
       || memcmp (a.buf1, "aabcdabcde", 10))
     FAIL ();
 
@@ -347,6 +360,7 @@ do_test (void)
   bcopy (buf + 1, buf + 2, l0 + 9);
   CHK_FAIL_END
 
+#ifdef _GNU_SOURCE
   CHK_FAIL_START
   p = (char *) mempcpy (buf + 6, "abcde", 5);
   CHK_FAIL_END
@@ -354,6 +368,7 @@ do_test (void)
   CHK_FAIL_START
   p = (char *) mempcpy (buf + 6, "abcde", l0 + 5);
   CHK_FAIL_END
+#endif
 
   CHK_FAIL_START
   memset (buf + 9, 'j', 2);
@@ -464,6 +479,7 @@ do_test (void)
   bcopy (a.buf1 + 1, a.buf1 + 2, l0 + 9);
   CHK_FAIL_END
 
+#ifdef _GNU_SOURCE
   CHK_FAIL_START
   p = (char *) mempcpy (a.buf1 + 6, "abcde", 5);
   CHK_FAIL_END
@@ -471,6 +487,7 @@ do_test (void)
   CHK_FAIL_START
   p = (char *) mempcpy (a.buf1 + 6, "abcde", l0 + 5);
   CHK_FAIL_END
+#endif
 
   CHK_FAIL_START
   memset (a.buf1 + 9, 'j', 2);
@@ -550,7 +567,7 @@ do_test (void)
   if (wmemcmp (wbuf, L"aabcdefghi", 10))
     FAIL ();
 
-  if (wmempcpy (wbuf + 5, L"abcde", 5) != wbuf + 10
+  if (WMEMPCPY (wbuf + 5, L"abcde", 5) != wbuf + 5 + WMEMPCPY_RET (L"abcde")
       || wmemcmp (wbuf, L"aabcdabcde", 10))
     FAIL ();
 
@@ -583,7 +600,8 @@ do_test (void)
   if (wmemcmp (wbuf, L"aabcdefghi", 10))
     FAIL ();
 
-  if (wmempcpy (wbuf + 5, L"abcde", l0 + 5) != wbuf + 10
+  if (WMEMPCPY (wbuf + 5, L"abcde", l0 + 5)
+      != wbuf + 5 + WMEMPCPY_RET (L"abcde")
       || wmemcmp (wbuf, L"aabcdabcde", 10))
     FAIL ();
 
@@ -625,7 +643,8 @@ do_test (void)
   if (wmemcmp (wa.buf1, L"aabcdefghi", 10))
     FAIL ();
 
-  if (wmempcpy (wa.buf1 + 5, L"abcde", l0 + 5) != wa.buf1 + 10
+  if (WMEMPCPY (wa.buf1 + 5, L"abcde", l0 + 5)
+      != wa.buf1 + 5 + WMEMPCPY_RET (L"abcde")
       || wmemcmp (wa.buf1, L"aabcdabcde", 10))
     FAIL ();
 
@@ -694,6 +713,7 @@ do_test (void)
   wmemmove (wbuf + 2, wbuf + 1, l0 + 9);
   CHK_FAIL_END
 
+#ifdef _GNU_SOURCE
   CHK_FAIL_START
   wp = wmempcpy (wbuf + 6, L"abcde", 5);
   CHK_FAIL_END
@@ -701,6 +721,7 @@ do_test (void)
   CHK_FAIL_START
   wp = wmempcpy (wbuf + 6, L"abcde", l0 + 5);
   CHK_FAIL_END
+#endif
 
   CHK_FAIL_START
   wmemset (wbuf + 9, L'j', 2);
@@ -768,6 +789,7 @@ do_test (void)
   wmemmove (wa.buf1 + 2, wa.buf1 + 1, l0 + 9);
   CHK_FAIL_END
 
+#ifdef _GNU_SOURCE
   CHK_FAIL_START
   wp = wmempcpy (wa.buf1 + 6, L"abcde", 5);
   CHK_FAIL_END
@@ -775,6 +797,7 @@ do_test (void)
   CHK_FAIL_START
   wp = wmempcpy (wa.buf1 + 6, L"abcde", l0 + 5);
   CHK_FAIL_END
+#endif
 
   CHK_FAIL_START
   wmemset (wa.buf1 + 9, L'j', 2);
@@ -906,6 +929,7 @@ do_test (void)
   if (fprintf (fp, buf2 + 4, str5) != 7)
     FAIL ();
 
+#ifdef _GNU_SOURCE
   char *my_ptr = NULL;
   strcpy (buf2 + 2, "%n%s%n");
   /* When the format string is writable and contains %n,
@@ -935,6 +959,7 @@ do_test (void)
   if (obstack_printf (&obs, "%s%n%s%n", str4, &n1, str5, &n1) != 14)
     FAIL ();
   obstack_free (&obs, NULL);
+#endif
 
   if (freopen (temp_filename, "r", stdin) == NULL)
     {
@@ -982,6 +1007,7 @@ do_test (void)
 
   rewind (stdin);
 
+#ifdef _GNU_SOURCE
   if (fgets_unlocked (buf, buf_size, stdin) != buf
       || memcmp (buf, "abcdefgh\n", 10))
     FAIL ();
@@ -1008,6 +1034,7 @@ do_test (void)
 #endif
 
   rewind (stdin);
+#endif
 
   if (fread (buf, 1, buf_size, stdin) != buf_size
       || memcmp (buf, "abcdefgh\nA", 10))
@@ -1578,7 +1605,10 @@ do_test (void)
       ret = 1;
     }
 
-  int fd = posix_openpt (O_RDWR);
+  int fd;
+
+#ifdef _GNU_SOURCE
+  fd = posix_openpt (O_RDWR);
   if (fd != -1)
     {
       char enough[1000];
@@ -1594,6 +1624,7 @@ do_test (void)
 #endif
       close (fd);
     }
+#endif
 
 #if PATH_MAX > 0
   confstr (_CS_GNU_LIBC_VERSION, largebuf, sizeof (largebuf));
@@ -1711,8 +1742,9 @@ do_test (void)
   poll (fds, l0 + 2, 0);
   CHK_FAIL_END
 #endif
+#ifdef _GNU_SOURCE
   ppoll (fds, 1, NULL, NULL);
-#if __USE_FORTIFY_LEVEL >= 1
+# if __USE_FORTIFY_LEVEL >= 1
   CHK_FAIL_START
   ppoll (fds, 2, NULL, NULL);
   CHK_FAIL_END
@@ -1720,6 +1752,7 @@ do_test (void)
   CHK_FAIL_START
   ppoll (fds, l0 + 2, NULL, NULL);
   CHK_FAIL_END
+# endif
 #endif
 
   return ret;
diff --git a/posix/bits/unistd.h b/posix/bits/unistd.h
index 01df84b5f9..f53a7a06eb 100644
--- a/posix/bits/unistd.h
+++ b/posix/bits/unistd.h
@@ -40,7 +40,7 @@ read (int __fd, void *__buf, size_t __nbytes)
 			  __fd, __buf, __nbytes);
 }
 
-#ifdef __USE_UNIX98
+#if defined __USE_UNIX98 || defined __USE_XOPEN2K8
 extern ssize_t __pread_chk (int __fd, void *__buf, size_t __nbytes,
 			    __off_t __offset, size_t __bufsize)
   __wur __attr_access ((__write_only__, 2, 3));
diff --git a/string/bits/string_fortified.h b/string/bits/string_fortified.h
index 51ad480401..f4a5dfc2e5 100644
--- a/string/bits/string_fortified.h
+++ b/string/bits/string_fortified.h
@@ -79,7 +79,7 @@ __NTH (strcpy (char *__restrict __dest, const char *__restrict __src))
   return __builtin___strcpy_chk (__dest, __src, __glibc_objsize (__dest));
 }
 
-#ifdef __USE_GNU
+#ifdef __USE_XOPEN2K8
 __fortify_function char *
 __NTH (stpcpy (char *__restrict __dest, const char *__restrict __src))
 {
@@ -96,14 +96,15 @@ __NTH (strncpy (char *__restrict __dest, const char *__restrict __src,
 				  __glibc_objsize (__dest));
 }
 
-#if __GNUC_PREREQ (4, 7) || __glibc_clang_prereq (2, 6)
+#ifdef __USE_XOPEN2K8
+# if __GNUC_PREREQ (4, 7) || __glibc_clang_prereq (2, 6)
 __fortify_function char *
 __NTH (stpncpy (char *__dest, const char *__src, size_t __n))
 {
   return __builtin___stpncpy_chk (__dest, __src, __n,
 				  __glibc_objsize (__dest));
 }
-#else
+# else
 extern char *__stpncpy_chk (char *__dest, const char *__src, size_t __n,
 			    size_t __destlen) __THROW
   __fortified_attr_access ((__write_only__, 1, 3))
@@ -119,6 +120,7 @@ __NTH (stpncpy (char *__dest, const char *__src, size_t __n))
     return __stpncpy_chk (__dest, __src, __n, __bos (__dest));
   return __stpncpy_alias (__dest, __src, __n);
 }
+# endif
 #endif
 
 
diff --git a/support/xsignal.h b/support/xsignal.h
index 973f532495..d868bb336c 100644
--- a/support/xsignal.h
+++ b/support/xsignal.h
@@ -28,7 +28,9 @@ __BEGIN_DECLS
    terminate the process on error.  */
 
 void xraise (int sig);
+#ifdef _GNU_SOURCE
 sighandler_t xsignal (int sig, sighandler_t handler);
+#endif
 void xsigaction (int sig, const struct sigaction *newact,
                  struct sigaction *oldact);
 
diff --git a/wcsmbs/bits/wchar2.h b/wcsmbs/bits/wchar2.h
index 25d06d433f..0e017f458b 100644
--- a/wcsmbs/bits/wchar2.h
+++ b/wcsmbs/bits/wchar2.h
@@ -457,7 +457,7 @@ __NTH (wcsrtombs (char *__restrict __dst, const wchar_t **__restrict __src,
 }
 
 
-#ifdef __USE_GNU
+#ifdef	__USE_XOPEN2K8
 extern size_t __mbsnrtowcs_chk (wchar_t *__restrict __dst,
 				const char **__restrict __src, size_t __nmc,
 				size_t __len, mbstate_t *__restrict __ps,