diff --git a/ChangeLog b/ChangeLog
index 96f6ce52d8..0c6b43ebc0 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,11 @@
 2018-11-01  Joseph Myers  <joseph@codesourcery.com>
 
+	* stdio-common/bug22.c: Include <libc-diag.h>.
+	(do_test): Disable -Wformat-overflow= warnings around fprintf
+	calls outputting more than INT_MAX characters.
+	* stdio-common/tst-printf.c: Disable -Wformat-overflow= warnings
+	around printf call with NULL %s argument.
+
 	[BZ #23848]
 	* sysdeps/unix/sysv/linux/sparc/kernel-features.h [!__arch64__ &&
 	__LINUX_KERNEL_VERSION < 0x040400] (__ASSUME_SENDMSG_SYSCALL):
diff --git a/stdio-common/bug22.c b/stdio-common/bug22.c
index b26399acb7..b3d48eb8e1 100644
--- a/stdio-common/bug22.c
+++ b/stdio-common/bug22.c
@@ -1,6 +1,7 @@
 /* BZ #5424 */
 #include <stdio.h>
 #include <errno.h>
+#include <libc-diag.h>
 
 /* INT_MAX + 1 */
 #define N 2147483648
@@ -30,12 +31,26 @@ do_test (void)
       return 1;
     }
 
+  /* GCC 9 warns about output of more than INT_MAX characters; this is
+     deliberately tested here.  */
+  DIAG_PUSH_NEEDS_COMMENT;
+#if __GNUC_PREREQ (7, 0)
+  DIAG_IGNORE_NEEDS_COMMENT (9, "-Wformat-overflow=");
+#endif
   ret = fprintf (fp, "%" SN "d", 1);
+  DIAG_POP_NEEDS_COMMENT;
   printf ("ret = %d\n", ret);
   if (ret != -1 || errno != EOVERFLOW)
 	  return 1;
 
+  /* GCC 9 warns about output of more than INT_MAX characters; this is
+     deliberately tested here.  */
+  DIAG_PUSH_NEEDS_COMMENT;
+#if __GNUC_PREREQ (7, 0)
+  DIAG_IGNORE_NEEDS_COMMENT (9, "-Wformat-overflow=");
+#endif
   ret = fprintf (fp, "%." SN "d", 1);
+  DIAG_POP_NEEDS_COMMENT;
   printf ("ret = %d\n", ret);
   if (ret != -1 || errno != EOVERFLOW)
 	  return 1;
@@ -45,7 +60,14 @@ do_test (void)
   if (ret != -1 || errno != EOVERFLOW)
 	  return 1;
 
+  /* GCC 9 warns about output of more than INT_MAX characters; this is
+     deliberately tested here.  */
+  DIAG_PUSH_NEEDS_COMMENT;
+#if __GNUC_PREREQ (7, 0)
+  DIAG_IGNORE_NEEDS_COMMENT (9, "-Wformat-overflow=");
+#endif
   ret = fprintf (fp, "%" SN2 "d%" SN2 "d", 1, 1);
+  DIAG_POP_NEEDS_COMMENT;
   printf ("ret = %d\n", ret);
 
   return ret != -1 || errno != EOVERFLOW;
diff --git a/stdio-common/tst-printf.c b/stdio-common/tst-printf.c
index 70d9e584b3..e4f4f1624d 100644
--- a/stdio-common/tst-printf.c
+++ b/stdio-common/tst-printf.c
@@ -110,7 +110,14 @@ I am ready for my first lesson today.";
   printf("left-adjusted Z string:\t\"%-010s\"\n", shortstr);
   printf("space-padded string:\t\"%10s\"\n", shortstr);
   printf("left-adjusted S string:\t\"%-10s\"\n", shortstr);
+  /* GCC 9 warns about the NULL format argument; this is deliberately
+     tested here.  */
+  DIAG_PUSH_NEEDS_COMMENT;
+#if __GNUC_PREREQ (7, 0)
+  DIAG_IGNORE_NEEDS_COMMENT (9, "-Wformat-overflow=");
+#endif
   printf("null string:\t\"%s\"\n", (char *)NULL);
+  DIAG_POP_NEEDS_COMMENT;
   printf("limited string:\t\"%.22s\"\n", longstr);
 
   printf("a-style max:\t\"%a\"\n", DBL_MAX);