selftests/bpf: Fix using stdout, stderr as struct field names

Typically stdin, stdout, stderr are treated as reserved identifiers under
ISO/ANSI C and libc implementations further define these as macros, both in
glibc and musl <stdio.h>.

However, while glibc defines:
    ...
    /* Standard streams.  */
    extern FILE *stdin;             /* Standard input stream.  */
    extern FILE *stdout;            /* Standard output stream.  */
    extern FILE *stderr;            /* Standard error output stream.  */
    /* C89/C99 say they're macros.  Make them happy.  */
    #define stdin stdin
    #define stdout stdout
    #define stderr stderr
    ...

musl instead uses (legally):
    ...
    extern FILE *const stdin;
    extern FILE *const stdout;
    extern FILE *const stderr;

    #define stdin  (stdin)
    #define stdout (stdout)
    #define stderr (stderr)
    ...

The latter results in compile errors when the names are reused as fields of
'struct test_env' and elsewhere in test_progs.[ch] and reg_bounds.c.

Rename the fields to stdout_saved and stderr_saved to avoid many errors
seen building against musl, e.g.:

  In file included from test_progs.h:6,
                   from test_progs.c:5:
  test_progs.c: In function 'print_test_result':
  test_progs.c:237:21: error: expected identifier before '(' token
    237 |         fprintf(env.stdout, "#%-*d %s:", TEST_NUM_WIDTH, test->test_num, test->test_name);
        |                     ^~~~~~
  test_progs.c:237:9: error: too few arguments to function 'fprintf'
    237 |         fprintf(env.stdout, "#%-*d %s:", TEST_NUM_WIDTH, test->test_num, test->test_name);
        |         ^~~~~~~
Signed-off-by: Tony Ambardar <tony.ambardar@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/ZqR2DuHdBXPX%2Fyx8@kodidev-ubuntu/
Link: https://lore.kernel.org/bpf/684ea17548e237f39dfb3f7a3d33450069015b21.1722244708.git.tony.ambardar@gmail.com

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

@@ -1487,7 +1487,7 @@ static int verify_case_opt(struct ctx *ctx, enum num_t init_t, enum num_t cond_t
 			u64 elapsed_ns = get_time_ns() - ctx->start_ns;
 			double remain_ns = elapsed_ns / progress * (1 - progress);
 
-			fprintf(env.stderr, "PROGRESS (%s): %d/%d (%.2lf%%), "
+			fprintf(env.stderr_saved, "PROGRESS (%s): %d/%d (%.2lf%%), "
 					    "elapsed %llu mins (%.2lf hrs), "
 					    "ETA %.0lf mins (%.2lf hrs)\n",
 				ctx->progress_ctx,

tools/testing/selftests/bpf/test_progs.c

@@ -51,15 +51,15 @@ static void stdio_hijack_init(char **log_buf, size_t *log_cnt)
 
 	stdout = open_memstream(log_buf, log_cnt);
 	if (!stdout) {
-		stdout = env.stdout;
+		stdout = env.stdout_saved;
 		perror("open_memstream");
 		return;
 	}
 
 	if (env.subtest_state)
-		env.subtest_state->stdout = stdout;
+		env.subtest_state->stdout_saved = stdout;
 	else
-		env.test_state->stdout = stdout;
+		env.test_state->stdout_saved = stdout;
 
 	stderr = stdout;
 #endif
@@ -73,8 +73,8 @@ static void stdio_hijack(char **log_buf, size_t *log_cnt)
 		return;
 	}
 
-	env.stdout = stdout;
-	env.stderr = stderr;
+	env.stdout_saved = stdout;
+	env.stderr_saved = stderr;
 
 	stdio_hijack_init(log_buf, log_cnt);
 #endif
@@ -91,13 +91,13 @@ static void stdio_restore_cleanup(void)
 	fflush(stdout);
 
 	if (env.subtest_state) {
-		fclose(env.subtest_state->stdout);
-		env.subtest_state->stdout = NULL;
-		stdout = env.test_state->stdout;
-		stderr = env.test_state->stdout;
+		fclose(env.subtest_state->stdout_saved);
+		env.subtest_state->stdout_saved = NULL;
+		stdout = env.test_state->stdout_saved;
+		stderr = env.test_state->stdout_saved;
 	} else {
-		fclose(env.test_state->stdout);
-		env.test_state->stdout = NULL;
+		fclose(env.test_state->stdout_saved);
+		env.test_state->stdout_saved = NULL;
 	}
 #endif
 }
@@ -110,13 +110,13 @@ static void stdio_restore(void)
 		return;
 	}
 
-	if (stdout == env.stdout)
+	if (stdout == env.stdout_saved)
 		return;
 
 	stdio_restore_cleanup();
 
-	stdout = env.stdout;
-	stderr = env.stderr;
+	stdout = env.stdout_saved;
+	stderr = env.stderr_saved;
 #endif
 }
 
@@ -244,25 +244,25 @@ static void print_test_result(const struct prog_test_def *test, const struct tes
 	int skipped_cnt = test_state->skip_cnt;
 	int subtests_cnt = test_state->subtest_num;
 
-	fprintf(env.stdout, "#%-*d %s:", TEST_NUM_WIDTH, test->test_num, test->test_name);
+	fprintf(env.stdout_saved, "#%-*d %s:", TEST_NUM_WIDTH, test->test_num, test->test_name);
 	if (test_state->error_cnt)
-		fprintf(env.stdout, "FAIL");
+		fprintf(env.stdout_saved, "FAIL");
 	else if (!skipped_cnt)
-		fprintf(env.stdout, "OK");
+		fprintf(env.stdout_saved, "OK");
 	else if (skipped_cnt == subtests_cnt || !subtests_cnt)
-		fprintf(env.stdout, "SKIP");
+		fprintf(env.stdout_saved, "SKIP");
 	else
-		fprintf(env.stdout, "OK (SKIP: %d/%d)", skipped_cnt, subtests_cnt);
+		fprintf(env.stdout_saved, "OK (SKIP: %d/%d)", skipped_cnt, subtests_cnt);
 
-	fprintf(env.stdout, "\n");
+	fprintf(env.stdout_saved, "\n");
 }
 
 static void print_test_log(char *log_buf, size_t log_cnt)
 {
 	log_buf[log_cnt] = '\0';
-	fprintf(env.stdout, "%s", log_buf);
+	fprintf(env.stdout_saved, "%s", log_buf);
 	if (log_buf[log_cnt - 1] != '\n')
-		fprintf(env.stdout, "\n");
+		fprintf(env.stdout_saved, "\n");
 }
 
 static void print_subtest_name(int test_num, int subtest_num,
@@ -273,14 +273,14 @@ static void print_subtest_name(int test_num, int subtest_num,
 
 	snprintf(test_num_str, sizeof(test_num_str), "%d/%d", test_num, subtest_num);
 
-	fprintf(env.stdout, "#%-*s %s/%s",
+	fprintf(env.stdout_saved, "#%-*s %s/%s",
 		TEST_NUM_WIDTH, test_num_str,
 		test_name, subtest_name);
 
 	if (result)
-		fprintf(env.stdout, ":%s", result);
+		fprintf(env.stdout_saved, ":%s", result);
 
-	fprintf(env.stdout, "\n");
+	fprintf(env.stdout_saved, "\n");
 }
 
 static void jsonw_write_log_message(json_writer_t *w, char *log_buf, size_t log_cnt)
@@ -465,7 +465,7 @@ bool test__start_subtest(const char *subtest_name)
 	memset(subtest_state, 0, sub_state_size);
 
 	if (!subtest_name || !subtest_name[0]) {
-		fprintf(env.stderr,
+		fprintf(env.stderr_saved,
 			"Subtest #%d didn't provide sub-test name!\n",
 			state->subtest_num);
 		return false;
@@ -473,7 +473,7 @@ bool test__start_subtest(const char *subtest_name)
 
 	subtest_state->name = strdup(subtest_name);
 	if (!subtest_state->name) {
-		fprintf(env.stderr,
+		fprintf(env.stderr_saved,
 			"Subtest #%d: failed to copy subtest name!\n",
 			state->subtest_num);
 		return false;
@@ -1043,7 +1043,7 @@ void crash_handler(int signum)
 
 	sz = backtrace(bt, ARRAY_SIZE(bt));
 
-	if (env.stdout)
+	if (env.stdout_saved)
 		stdio_restore();
 	if (env.test) {
 		env.test_state->error_cnt++;
@@ -1359,7 +1359,7 @@ static void calculate_summary_and_print_errors(struct test_env *env)
 	if (env->json) {
 		w = jsonw_new(env->json);
 		if (!w)
-			fprintf(env->stderr, "Failed to create new JSON stream.");
+			fprintf(env->stderr_saved, "Failed to create new JSON stream.");
 	}
 
 	if (w) {
@@ -1708,8 +1708,8 @@ int main(int argc, char **argv)
 		return -1;
 	}
 
-	env.stdout = stdout;
-	env.stderr = stderr;
+	env.stdout_saved = stdout;
+	env.stderr_saved = stderr;
 
 	env.has_testmod = true;
 	if (!env.list_test_names) {
@@ -1717,7 +1717,7 @@ int main(int argc, char **argv)
 		unload_bpf_testmod(verbose());
 
 		if (load_bpf_testmod(verbose())) {
-			fprintf(env.stderr, "WARNING! Selftests relying on bpf_testmod.ko will be skipped.\n");
+			fprintf(env.stderr_saved, "WARNING! Selftests relying on bpf_testmod.ko will be skipped.\n");
 			env.has_testmod = false;
 		}
 	}
@@ -1795,7 +1795,7 @@ int main(int argc, char **argv)
 		}
 
 		if (env.list_test_names) {
-			fprintf(env.stdout, "%s\n", test->test_name);
+			fprintf(env.stdout_saved, "%s\n", test->test_name);
 			env.succ_cnt++;
 			continue;
 		}

tools/testing/selftests/bpf/test_progs.h

@@ -75,7 +75,7 @@ struct subtest_state {
 	bool skipped;
 	bool filtered;
 
-	FILE *stdout;
+	FILE *stdout_saved;
 };
 
 struct test_state {
@@ -92,7 +92,7 @@ struct test_state {
 	size_t log_cnt;
 	char *log_buf;
 
-	FILE *stdout;
+	FILE *stdout_saved;
 };
 
 struct test_env {
@@ -111,8 +111,8 @@ struct test_env {
 	struct test_state *test_state; /* current running test state */
 	struct subtest_state *subtest_state; /* current running subtest state */
 
-	FILE *stdout;
-	FILE *stderr;
+	FILE *stdout_saved;
+	FILE *stderr_saved;
 	int nr_cpus;
 	FILE *json;