[PATCH bpf-next v2 7/7] selftests/bpf: Skip compare_text subtest when stdout is not saved

[KaFai Wan]

stdio_hijack_init() does not set subtest_state->stdout_saved when
running with -v in non-parallel mode, since output goes straight to
stdout. In that case subtest_state->log_buf is left NULL, so the
compare_text_mismatch subtest crashes when inspecting it. Skip it when
stdout was not saved.

Fixes: bd71904697c6 ("selftests/bpf: Add compare_text_to_expected() helper")
Signed-off-by: KaFai Wan <kafai....@linux.dev>
---
 .../bpf/prog_tests/prog_tests_framework.c      | 18 +++++++++++-------
 1 file changed, 11 insertions(+), 7 deletions(-)

diff --git a/tools/testing/selftests/bpf/prog_tests/prog_tests_framework.c 
b/tools/testing/selftests/bpf/prog_tests/prog_tests_framework.c
index b4cd7c7ff4391..ddb6cdc1579f1 100644
--- a/tools/testing/selftests/bpf/prog_tests/prog_tests_framework.c
+++ b/tools/testing/selftests/bpf/prog_tests/prog_tests_framework.c
@@ -203,14 +203,18 @@ void test_prog_tests_framework_compare_text(void)
        }
 
        if (test__start_subtest("compare_text_mismatch")) {
-               err = compare_text_to_expected("line two\n", "line one\n");
-               fflush(stdout);
+               if (!env.subtest_state->stdout_saved) {
+                       test__skip();
+               } else {
+                       err = compare_text_to_expected("line two\n", "line 
one\n");
+                       fflush(stdout);
 
-               ASSERT_EQ(err, -1, "mismatch_rc");
-               ASSERT_HAS_SUBSTR(env.subtest_state->log_buf, "-line one",
-                                 "diff_has_expected");
-               ASSERT_HAS_SUBSTR(env.subtest_state->log_buf, "+line two",
-                                 "diff_has_actual");
+                       ASSERT_EQ(err, -1, "mismatch_rc");
+                       ASSERT_HAS_SUBSTR(env.subtest_state->log_buf, "-line 
one",
+                                         "diff_has_expected");
+                       ASSERT_HAS_SUBSTR(env.subtest_state->log_buf, "+line 
two",
+                                         "diff_has_actual");
+               }
                test__end_subtest();
        }
 }
-- 
2.43.0