test(extern): check variadic promotions with va_arg

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

1 files changed, 20 insertions, 0 deletions

diff --git a/tests/i/extern-c-variadic/lib.c b/tests/i/extern-c-variadic/lib.c
new file mode 100644
index 0000000..8f723a5
--- /dev/null
+++ b/tests/i/extern-c-variadic/lib.c
@@ -0,0 +1,20 @@
+#include <stdarg.h>
+
+/* Each argument after n arrives promoted, so va_arg reads int or double. */
+int sum_ints(int n, ...) {
+    va_list ap;
+    int total = 0;
+    va_start(ap, n);
+    for (int i = 0; i < n; ++i) total += va_arg(ap, int);
+    va_end(ap);
+    return total;
+}
+
+double sum_doubles(int n, ...) {
+    va_list ap;
+    double total = 0;
+    va_start(ap, n);
+    for (int i = 0; i < n; ++i) total += va_arg(ap, double);
+    va_end(ap);
+    return total;
+}