Merge pull request #2570 from sidneycadot/struct-assignment-bug2566

Added test to demonstrate issue #2566.

test/todo/bug2566.c

@@ -0,0 +1,49 @@
+
+/* Regression test for https://github.com/cc65/cc65/issues/2566
+ *
+ * The issue was introduced in an innocious-looking commit back in 2020:
+ *
+ * https://github.com/cc65/cc65/commit/c3a6b399456937093eda9994f19b7f722731528d
+ *
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdbool.h>
+
+typedef struct {
+    unsigned long Field1;
+    unsigned long Field2;
+} RecordType;
+
+typedef struct {
+    char dummy; // -- Offsets the Rec field by 1 byte.
+    RecordType Rec;
+} StructTypeA;
+
+typedef struct {
+    RecordType Rec;
+} StructTypeB;
+
+int main(void)
+{
+    StructTypeA A, *Aptr;
+    StructTypeB B;
+    bool ok;
+
+    A.Rec.Field1 = 0x11111111;
+    A.Rec.Field2 = 0x22222222;
+
+    Aptr = &A;
+    B.Rec = Aptr->Rec;
+
+    /* These print statements give some clues as to what's going on. */
+    /*
+    printf("A.Rec: %lx, %lx\n", A.Rec.Field1, A.Rec.Field2);
+    printf("B.Rec: %lx, %lx\n", B.Rec.Field1, B.Rec.Field2);
+    */
+
+    ok = (A.Rec.Field1 == B.Rec.Field1 && A.Rec.Field2 == B.Rec.Field2);
+
+    return ok ? EXIT_SUCCESS : EXIT_FAILURE;
+}