[PATCH 2/2] libtraceevent utest: Avoid host-specific getname_flags output

[Cao Ruichuang <create0818@163.com>]

test_btf_read() loads /sys/kernel/btf/vmlinux and expects
getname_flags() to print exactly two arguments:

  getname_flags(filename=0x7ffe7d33f3d0, flags=0)

That prototype is not stable across kernels. On a Rocky Linux 9.7
system, the kernel BTF for getname_flags() has a third parameter named
empty, and tep_btf_print_args() correctly prints it.

Keep the exact output check for hosts that match the expected prototype.
For hosts that append extra getname_flags() BTF parameters after the
expected arguments, treat that host-specific suffix as an acceptable
variant only if the output still has the expected argument prefix and a
complete closing suffix.

Fixes: 0294b73f17e9 ("libtraceevent utest: Add simple test to test BTF parsing")
Assisted-by: Codex:gpt-5.5
Signed-off-by: Cao Ruichuang <create0818@163.com>
---
 utest/traceevent-utest.c | 20 +++++++++++++++++++-
 1 file changed, 19 insertions(+), 1 deletion(-)

diff --git a/utest/traceevent-utest.c b/utest/traceevent-utest.c
index b93d686..04f6726 100644
--- a/utest/traceevent-utest.c
+++ b/utest/traceevent-utest.c
@@ -16,6 +16,7 @@
 #include <time.h>
 #include <dirent.h>
 #include <ftw.h>
+#include <string.h>
 
 #include <sys/mman.h>
 #include <stdint.h>
@@ -529,10 +530,21 @@ static int read_full(int fd, void *buf, size_t size)
 	return 0;
 }
 
+static bool output_has_extra_args(const char *output, const char *prefix)
+{
+	size_t len = strlen(output);
+	size_t plen = strlen(prefix);
+
+	return len > plen + 3 && strncmp(output, prefix, plen) == 0 &&
+	       output[plen] == ',' && strcmp(output + len - 2, ")\n") == 0;
+}
+
 static void test_btf_read(void)
 {
 	uint64_t args[] = {0x7ffe7d33f3d0, 0, 0, 0, 0, 0};
 	const char *func = "getname_flags";
+	const char *expected = "getname_flags(filename=0x7ffe7d33f3d0, flags=0)\n";
+	const char *expected_prefix = "getname_flags(filename=0x7ffe7d33f3d0, flags=0";
 	struct trace_seq *s = test_seq;
 	struct stat st;
 	void *buf;
@@ -582,7 +594,13 @@ static void test_btf_read(void)
 	trace_seq_puts(s, ")\n");
 	trace_seq_terminate(s);
 
-	CU_TEST(strcmp(s->buffer, "getname_flags(filename=0x7ffe7d33f3d0, flags=0)\n") == 0);
+	if (strcmp(s->buffer, expected) != 0 &&
+	    output_has_extra_args(s->buffer, expected_prefix)) {
+		printf("[KERNEL BTF HAS EXTRA getname_flags ARGS] ...");
+		return;
+	}
+
+	CU_TEST(strcmp(s->buffer, expected) == 0);
 }
 
 static int test_suite_destroy(void)
-- 
2.39.5 (Apple Git-154)