[COMMITTED] Eliminate -Wno-format from printf/scanf tests.

--- a/stdio-common/Makefile
+++ b/stdio-common/Makefile
@@ -80,11 +80,6 @@  endif
 
 CFLAGS-vfprintf.c = -Wno-uninitialized
 CFLAGS-vfwprintf.c = -Wno-uninitialized
-CFLAGS-tst-printf.c = -Wno-format
-CFLAGS-tstdiomisc.c = -Wno-format
-CFLAGS-scanf4.c = -Wno-format
-CFLAGS-scanf7.c = -Wno-format
-CFLAGS-tst-printfsz.c = -Wno-format
 
 CFLAGS-tmpfile.c = -fexceptions
 CFLAGS-tmpfile64.c = -fexceptions
@@ -116,9 +111,6 @@  CFLAGS-scanf15.c = -I../libio -I../stdlib -I../wcsmbs -I../time -I../string \
 CFLAGS-scanf17.c = -I../libio -I../stdlib -I../wcsmbs -I../time -I../string \
 		   -I../wctype
 
-# We know the test has a format string problem.
-CFLAGS-tst-sprintf.c = -Wno-format
-
 CPPFLAGS += $(libio-mtsafe)
 
 $(objpfx)tst-setvbuf1.out: /dev/null $(objpfx)tst-setvbuf1
--- a/stdio-common/scanf4.c
+++ b/stdio-common/scanf4.c
@@ -1,5 +1,6 @@ 
 #include <stdio.h>
 #include <stdlib.h>
+#include <libc-internal.h>
 
 int
 main(int arc, char *argv[])
@@ -15,7 +16,14 @@  main(int arc, char *argv[])
   printf("Result of fscanf %%n = %d\n", res);
   printf("Scanned format = %d\n", val);
 
+  /* We're testing exactly the case the warning is for.  */
+  DIAG_PUSH_NEEDS_COMMENT;
+  DIAG_IGNORE_NEEDS_COMMENT (4.9, "-Wformat-zero-length");
+
   res = fscanf(fp, "");
+
+  DIAG_POP_NEEDS_COMMENT;
+
   printf("Result of fscanf \"\" = %d\n", res);
   if (res != 0)
     abort ();
--- a/stdio-common/scanf7.c
+++ b/stdio-common/scanf7.c
@@ -1,5 +1,6 @@ 
 #include <stdio.h>
 #include <stdlib.h>
+#include <libc-internal.h>
 
 int
 main (int argc, char *argv[])
@@ -14,7 +15,16 @@  main (int argc, char *argv[])
     abort ();
 
   n = -2;
+
+  /* We are testing a corner case of the scanf format string here.  */
+  DIAG_PUSH_NEEDS_COMMENT;
+  DIAG_IGNORE_NEEDS_COMMENT (4.9, "-Wformat");
+  DIAG_IGNORE_NEEDS_COMMENT (4.9, "-Wformat-extra-args");
+
   ret = sscanf ("1000", "%llld", &n);
+
+  DIAG_POP_NEEDS_COMMENT;
+
   printf ("%%llld: ret: %d, n: %Ld\n", ret, n);
   if (ret > 0 || n >= 0L)
     abort ();
--- a/stdio-common/test-vfprintf.c
+++ b/stdio-common/test-vfprintf.c
@@ -92,7 +92,13 @@  do_test (void)
       fprintf (fp, "%s", large);
       fprintf (fp, "%.*s", 30000, large);
       large[20000] = '\0';
+      /* We're testing a large format string here and need to generate it
+         to avoid this source file being ridiculous.  So disable the warning
+         about a generated format string.  */
+      DIAG_PUSH_NEEDS_COMMENT;
+      DIAG_IGNORE_NEEDS_COMMENT (4.9, "-Wformat-security");
       fprintf (fp, large);
+      DIAG_POP_NEEDS_COMMENT;
       fprintf (fp, "%-1.300000000s", "hello");
 
       if (fflush (fp) != 0 || ferror (fp) != 0 || fclose (fp) != 0)
--- a/stdio-common/tst-printf.c
+++ b/stdio-common/tst-printf.c
@@ -26,6 +26,11 @@ 
 #endif
 
 #include <float.h>
+#include <libc-internal.h>
+
+/* This whole file is picayune tests of corner cases of printf format strings.
+   The compiler warnings are not useful here.  */
+DIAG_IGNORE_NEEDS_COMMENT (4.9, "-Wformat");
 
 static void rfg1 (void);
 static void rfg2 (void);
--- a/stdio-common/tst-printfsz.c
+++ b/stdio-common/tst-printfsz.c
@@ -23,6 +23,10 @@  main (int argc, char *argv[])
   register_printf_function ('B', printf_size, printf_size_info);
   DIAG_POP_NEEDS_COMMENT;
 
+  /* All of the formats here use the nonstandard extension specifier
+     just registered, so compiler checking will never grok them.  */
+  DIAG_IGNORE_NEEDS_COMMENT (4.9, "-Wformat");
+  DIAG_IGNORE_NEEDS_COMMENT (4.9, "-Wformat-extra-args");
 
   sprintf (buf, "%g %b %B %.0b %.0B %.1b %.1B %8.0b %08.0B",
 	   V, 1025., V, V, V, V, V, V, V, V);
--- a/stdio-common/tst-sprintf.c
+++ b/stdio-common/tst-sprintf.c
@@ -45,15 +45,26 @@  do_test (void)
       result = 1;
     }
 
-  if (sprintf (buf, "%67108863.16\"%d", 7) != 14
-      || strcmp (buf, "%67108863.16\"7") != 0)
+  /* We are testing a corner case of the sprintf format string here.  */
+  DIAG_PUSH_NEEDS_COMMENT;
+  DIAG_IGNORE_NEEDS_COMMENT (4.9, "-Wformat");
+  int n = sprintf (buf, "%67108863.16\"%d", 7);
+  DIAG_POP_NEEDS_COMMENT;
+
+  if (n != 14 || strcmp (buf, "%67108863.16\"7") != 0)
     {
-      printf ("sprintf (buf, \"%%67108863.16\\\"%%d\", 7) produced `%s' output", buf);
+      printf ("sprintf (buf, \"%%67108863.16\\\"%%d\", 7) produced `%s' output",
+              buf);
       result = 1;
     }
 
-  if (sprintf (buf, "%*\"%d", 0x3ffffff, 7) != 11
-      || strcmp (buf, "%67108863\"7") != 0)
+  /* We are testing a corner case of the sprintf format string here.  */
+  DIAG_PUSH_NEEDS_COMMENT;
+  DIAG_IGNORE_NEEDS_COMMENT (4.9, "-Wformat");
+  n = sprintf (buf, "%*\"%d", 0x3ffffff, 7);
+  DIAG_POP_NEEDS_COMMENT;
+
+  if (n != 11 || strcmp (buf, "%67108863\"7") != 0)
     {
       printf ("sprintf (buf, \"%%*\\\"%%d\", 0x3ffffff, 7) produced `%s' output", buf);
       result = 1;
--- a/stdio-common/tstdiomisc.c
+++ b/stdio-common/tstdiomisc.c
@@ -3,6 +3,7 @@ 
 #include <stdio.h>
 #include <string.h>
 #include <wchar.h>
+#include <libc-internal.h>
 
 static int
 t1 (void)
@@ -28,6 +29,12 @@  t2 (void)
 	  INPUT, FORMAT, retval, (long int) VAR); \
   result |= retval != EXP_RES || VAR != EXP_VAL
 
+  /* This function is testing corner cases of the scanf format string,
+     so they do not all conform to -Wformat's expectations.  */
+  DIAG_PUSH_NEEDS_COMMENT;
+  DIAG_IGNORE_NEEDS_COMMENT (4.9, "-Wformat");
+  DIAG_IGNORE_NEEDS_COMMENT (4.9, "-Wformat-extra-args");
+
   SCAN ("12345", "%ld", N, 1, 12345);
   SCAN ("12345", "%llllld", N, 0, -1);
   SCAN ("12345", "%LLLLLd", N, 0, -1);
@@ -43,6 +50,8 @@  t2 (void)
 	  retval, n, N); \
   result |= retval != 1 || n != 1 || N != -1;
 
+  DIAG_POP_NEEDS_COMMENT;
+
   return result;
 }