[PATCH v4 bpf-next 9/9] selftests/bpf: Add test for bpf_printk w/ 0 fmt args

[Dave Marchevsky <davemarchevsky@xxxxxx>]

This corner case isn't covered by existing selftests' use of bpf_printk.

Just test compilation, not output, as trace_vprintk already tests
trace_pipe output.

Signed-off-by: Dave Marchevsky <davemarchevsky@xxxxxx>
---
 tools/testing/selftests/bpf/progs/trace_vprintk.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/tools/testing/selftests/bpf/progs/trace_vprintk.c b/tools/testing/selftests/bpf/progs/trace_vprintk.c
index 255e2f018efe..33455e48a9ab 100644
--- a/tools/testing/selftests/bpf/progs/trace_vprintk.c
+++ b/tools/testing/selftests/bpf/progs/trace_vprintk.c
@@ -23,3 +23,10 @@ int sys_enter(void *ctx)
 		one, 2, three, 4, five, 6, seven, 8, nine, 10, ++trace_vprintk_ran);
 	return 0;
 }
+
+SEC("fentry/__x64_sys_nanosleep")
+int zero_fmt_args(void *ctx)
+{
+	bpf_printk("\t"); // runner doesn't search for this, just ensure it compiles
+	return 0;
+}
-- 
2.30.2