Fix gcc 9 build errors for make xcheck.

commit 22e4ba39c88bcb2c75e8f038551cd75362c17298
Author: Stefan Liebler <stli@linux.ibm.com>
Date:   Fri Jun 14 12:54:38 2019 +0200

    Fix gcc 9 build errors for make xcheck. [BZ #24556]
    
    This patch fixes the following gcc 9 warnings for "make xcheck" / "make bench":
    -string/tst-strcasestr.c:
    ../include/bits/../../misc/bits/error.h:42:5: error: ‘%s’ directive argument is null [-Werror=format-overflow=]
    
    -argp/argp-test.c:
    argp-test.c:130:20: error: ‘%d’ directive writing between 1 and 11 bytes into a region of size 10 [-Werror=format-overflow=]
    argp-test.c:130:19: note: directive argument in the range [-2147483648, 122]
    argp-test.c:130:5: note: ‘sprintf’ output between 2 and 12 bytes into a destination of size 10
    
    -nss/tst-field.c:
    tst-field.c:52:7: error: ‘%s’ directive argument is null [-Werror=format-overflow=]
     Please enter the commit message for your changes. Lines starting
    
    -benchtests/bench-strstr.c:
    ../include/bits/../../misc/bits/error.h:42:5: error: ‘%s’ directive argument is null [-Werror=format-overflow=]
    
    -benchtests/bench-malloc-simple.c:
    bench-malloc-simple.c:93:16: error: iteration 3 invokes undefined behavior [-Werror=aggressive-loop-optimizations]
    
    ChangeLog:
    
            [BZ #24556]
            * string/test-strcasestr.c (check_result): Add NULL check.
            * nss/tst-field.c (check_rewrite): Likewise.
            * benchtests/bench-strstr.c (do_one_test): Likewise.
            * string/test-strstr.c (check_result): Likewise.
            * argp/argp-test.c (popt): Increase size of buf to 12.
            * benchtests/bench-malloc-simple.c (bench):
            Do not initialize tests array out of bounds.
    
    meld

diff --git a/argp/argp-test.c b/argp/argp-test.c
index cb2976ddad..13e0c6df14 100644
--- a/argp/argp-test.c
+++ b/argp/argp-test.c
@@ -123,7 +123,7 @@  static const char doc[] = "Test program for argp."
 static void
 popt (int key, char *arg)
 {
-  char buf[10];
+  char buf[12];
   if (isprint (key))
     sprintf (buf, "%c", key);
   else
diff --git a/benchtests/bench-malloc-simple.c b/benchtests/bench-malloc-simple.c
index b8bb2cc116..c4f06f6999 100644
--- a/benchtests/bench-malloc-simple.c
+++ b/benchtests/bench-malloc-simple.c
@@ -87,7 +87,7 @@  bench (unsigned long size)
   size_t iters = NUM_ITERS;
   int **arr = (int**) malloc (MAX_ALLOCS * sizeof (void*));
 
-  for (int t = 0; t <= 3; t++)
+  for (int t = 0; t < 3; t++)
     for (int i = 0; i < NUM_ALLOCS; i++)
       {
 	tests[t][i].n = allocs[i];
diff --git a/benchtests/bench-strstr.c b/benchtests/bench-strstr.c
index 2cbe13e9ac..c1cdcdd5bb 100644
--- a/benchtests/bench-strstr.c
+++ b/benchtests/bench-strstr.c
@@ -147,7 +147,8 @@  do_one_test (impl_t *impl, const char *s1, const char *s2, char *exp_result)
   if (res != exp_result)
     {
       error (0, 0, "Wrong result in function %s %s %s", impl->name,
-	     res, exp_result);
+	     (res == NULL) ? "NULL" : res,
+	     (exp_result == NULL) ? "NULL" : exp_result);
       ret = 1;
     }
 }
diff --git a/nss/tst-field.c b/nss/tst-field.c
index 23d2f2abf6..5c553e5f46 100644
--- a/nss/tst-field.c
+++ b/nss/tst-field.c
@@ -50,7 +50,7 @@  check_rewrite (const char *input, const char *expected)
   if (result != NULL && strcmp (result, expected) != 0)
     {
       printf ("FAIL: rewrite \"%s\" -> \"%s\", expected \"%s\"\n",
-	      input, result, expected);
+	      (input == NULL) ? "NULL" : input, result, expected);
       errors = true;
     }
   free (to_free);
diff --git a/string/test-strcasestr.c b/string/test-strcasestr.c
index 0a16f85dcd..f7cbcc14ef 100644
--- a/string/test-strcasestr.c
+++ b/string/test-strcasestr.c
@@ -67,7 +67,8 @@  check_result (impl_t *impl, const char *s1, const char *s2,
   if (result != exp_result)
     {
       error (0, 0, "Wrong result in function %s %s %s", impl->name,
-	     result, exp_result);
+	     (result == NULL) ? "NULL" : result,
+	     (exp_result == NULL) ? "NULL" : exp_result);
       ret = 1;
       return -1;
     }
diff --git a/string/test-strstr.c b/string/test-strstr.c
index 031aff5534..17d505a228 100644
--- a/string/test-strstr.c
+++ b/string/test-strstr.c
@@ -66,7 +66,8 @@  check_result (impl_t *impl, const char *s1, const char *s2,
   if (result != exp_result)
     {
       error (0, 0, "Wrong result in function %s %s %s", impl->name,
-	     result, exp_result);
+	     (result == NULL) ? "NULL" : result,
+	     (exp_result == NULL) ? "NULL" : exp_result);
       ret = 1;
       return -1;
     }