purego: add FourInt32s struct argument test case

Adds test coverage for struct arguments containing four int32 fields to
validate proper struct packing and argument marshalling. The test ensures
that all four int32 values are correctly passed to the C function and can
be retrieved and formatted as expected.

This test case helps verify the Darwin ARM64 struct packing improvements
handle multiple small integer fields within a single struct correctly.

Author: tmc

struct_test.go

@@ -486,6 +486,18 @@ func TestRegisterFunc_structArgs(t *testing.T) {
 			t.Fatalf("FloatAndBool(y: false) = %d, want 0", ret)
 		}
 	}
+	{
+		type FourInt32s struct {
+			f0, f1, f2, f3 int32
+		}
+		var FourInt32sFn func(FourInt32s) string
+		purego.RegisterLibFunc(&FourInt32sFn, lib, "FourInt32s")
+		result := FourInt32sFn(FourInt32s{1, 2, 3, 4})
+		const want = "1:2:3:4"
+		if result != want {
+			t.Fatalf("FourInt32s returned %q wanted %q", result, want)
+		}
+	}
 }
 
 func TestRegisterFunc_structReturns(t *testing.T) {

testdata/structtest/struct_test.c

@@ -361,3 +361,19 @@ struct FloatAndBool {
 int FloatAndBool(struct FloatAndBool f) {
     return f.has_value;
 }
+
+struct FourInt32s {
+    int32_t f0;
+    int32_t f1;
+    int32_t f2;
+    int32_t f3;
+};
+
+#include <stdio.h>
+#include <stdlib.h>
+
+char* FourInt32s(struct FourInt32s s) {
+    char* result = malloc(64);
+    snprintf(result, 64, "%d:%d:%d:%d", s.f0, s.f1, s.f2, s.f3);
+    return result;
+}