1 files changed, 12 insertions, 0 deletions
diff --git a/tests/i/extern-c-struct/lib.c b/tests/i/extern-c-struct/lib.c
index 39380ec..65080f1 100644
--- a/tests/i/extern-c-struct/lib.c
+++ b/tests/i/extern-c-struct/lib.c
@@ -1,3 +1,5 @@
+#include <stdarg.h>
+
 struct Sample {
     char tag;
     double value;
@@ -9,3 +11,13 @@ static struct Sample shared = {'G', 0.5, 7};
 void scale_sample(struct Sample *s, int k) { s->value *= k; }
 struct Sample *shared_sample(void) { return &shared; }
 int shared_count(void) { return shared.count; }
+
+/* Each argument after n is a struct Sample *, read back with va_arg. */
+int sum_counts(int n, ...) {
+    va_list ap;
+    int total = 0;
+    va_start(ap, n);
+    for (int i = 0; i < n; ++i) total += va_arg(ap, struct Sample *)->count;
+    va_end(ap);
+    return total;
+}