1 files changed, 38 insertions, 0 deletions
diff --git a/2025-linuxdays/priv.c b/2025-linuxdays/priv.c
new file mode 100644
index 0000000..ed3ad1a
--- /dev/null
+++ b/2025-linuxdays/priv.c
@@ -0,0 +1,38 @@
+#include <stddef.h>
+#include <stdio.h>
+
+struct pub {
+  void (*print_name)(struct pub *);
+};
+typedef struct pub *pub_t;
+#define pub_print_name(PUB) (PUB)->print_name(PUB)
+
+struct priv {
+  struct pub pub;
+  const char *name;
+};
+void pname_priv(struct pub *pub) {
+  struct priv *priv = (struct priv *)pub;
+  printf("%s", priv->name);
+}
+
+struct wrap {
+  struct pub *subpub;
+  struct pub pub;
+};
+void pname_wrap(struct pub *pub) {
+  struct wrap *wrap = (void *)pub - offsetof(struct wrap, pub);
+  printf("Wrap: ");
+  wrap->subpub->print_name(wrap->subpub);
+}
+
+int main(int argc, char *argv[]) {
+  struct priv priv = {.pub = {pname_priv}, .name = "FOO"};
+  pub_t p = &priv.pub;
+  pub_print_name(p);
+  putchar('\n');
+
+  struct wrap wrap = {.pub = {pname_wrap}, .subpub = &priv.pub};
+  wrap.pub.print_name(&wrap.pub);
+  putchar('\n');
+}