selftests/bpf: Fix a few compiler warnings

With clang building selftests/bpf, I hit a few warnings like below:

  .../bpf_iter.c:592:48: warning: variable 'expected_key_c' set but not used [-Wunused-but-set-variable]
  __u32 expected_key_a = 0, expected_key_b = 0, expected_key_c = 0;
                                                ^

  .../bpf_iter.c:688:48: warning: variable 'expected_key_c' set but not used [-Wunused-but-set-variable]
  __u32 expected_key_a = 0, expected_key_b = 0, expected_key_c = 0;
                                                ^

  .../tc_redirect.c:657:6: warning: variable 'target_fd' is used uninitialized whenever 'if' condition is true [-Wsometimes-uninitialized]
  if (!ASSERT_OK_PTR(nstoken, "setns " NS_FWD))
      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  .../tc_redirect.c:743:6: note: uninitialized use occurs here
  if (target_fd >= 0)
      ^~~~~~~~~

Removing unused variables and initializing the previously-uninitialized variable
to ensure these warnings are gone.
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20210917043343.3711917-1-yhs@fb.com

tools/testing/selftests/bpf/prog_tests/bpf_iter.c

@@ -589,7 +589,7 @@ static void test_overflow(bool test_e2big_overflow, bool ret1)
 
 static void test_bpf_hash_map(void)
 {
-	__u32 expected_key_a = 0, expected_key_b = 0, expected_key_c = 0;
+	__u32 expected_key_a = 0, expected_key_b = 0;
 	DECLARE_LIBBPF_OPTS(bpf_iter_attach_opts, opts);
 	struct bpf_iter_bpf_hash_map *skel;
 	int err, i, len, map_fd, iter_fd;
@@ -638,7 +638,6 @@ static void test_bpf_hash_map(void)
 		val = i + 4;
 		expected_key_a += key.a;
 		expected_key_b += key.b;
-		expected_key_c += key.c;
 		expected_val += val;
 
 		err = bpf_map_update_elem(map_fd, &key, &val, BPF_ANY);
@@ -685,7 +684,7 @@ static void test_bpf_hash_map(void)
 
 static void test_bpf_percpu_hash_map(void)
 {
-	__u32 expected_key_a = 0, expected_key_b = 0, expected_key_c = 0;
+	__u32 expected_key_a = 0, expected_key_b = 0;
 	DECLARE_LIBBPF_OPTS(bpf_iter_attach_opts, opts);
 	struct bpf_iter_bpf_percpu_hash_map *skel;
 	int err, i, j, len, map_fd, iter_fd;
@@ -722,7 +721,6 @@ static void test_bpf_percpu_hash_map(void)
 		key.c = i + 3;
 		expected_key_a += key.a;
 		expected_key_b += key.b;
-		expected_key_c += key.c;
 
 		for (j = 0; j < bpf_num_possible_cpus(); j++) {
 			*(__u32 *)(val + j * 8) = i + j;

tools/testing/selftests/bpf/prog_tests/tc_redirect.c

@@ -633,7 +633,7 @@ static void test_tc_redirect_peer_l3(struct netns_setup_result *setup_result)
 	struct nstoken *nstoken = NULL;
 	int err;
 	int tunnel_pid = -1;
-	int src_fd, target_fd;
+	int src_fd, target_fd = -1;
 	int ifindex;
 
 	/* Start a L3 TUN/TAP tunnel between the src and dst namespaces.