1 files changed, 90 insertions, 1 deletions
diff --git a/man3/_Generic.3 b/man3/_Generic.3
index ddee5f6c4c..6ff5e24ea7 100644
--- a/man3/_Generic.3
+++ b/man3/_Generic.3
@@ -27,12 +27,101 @@ that will behave differently depending on the type of the argument.
 .SH STANDARDS
 C11 and later.
 .SH EXAMPLES
+The following code demonstrates how to write
+a macro similar to C++'s
+.BR \%static_cast (),
+which will allow casting safely between a limited set of types.
+It is useful for example when calling
+system calls or library functions that use compatible structures,
+like for example
+.BR bind (2)
+with
+.BR \%sockaddr (3type).
+.IP
+.EX
+/* This code is in the public domain. */
+
+#include <netinet/in.h>
+#include <sys/socket.h>
+#include <sys/un.h>
+
+#define sockaddr_cast(t, p)                            \e
+    _Generic(&*(p),                                    \e
+    struct sockaddr *:                                 \e
+        _Generic((typeof_unqual(t)) NULL,              \e
+        struct sockaddr_in *:             (t) (p),     \e
+        struct sockaddr_in6 *:            (t) (p),     \e
+        struct sockaddr_un *:             (t) (p),     \e
+        default:                              (p)),    \e
+    struct sockaddr **:                                \e
+        _Generic((typeof_unqual(t)) NULL,              \e
+        struct sockaddr_in **:            (t) (p),     \e
+        struct sockaddr_in6 **:           (t) (p),     \e
+        struct sockaddr_un **:            (t) (p),     \e
+        default:                              (p)),    \e
+    const struct sockaddr *:                           \e
+        _Generic((t) NULL,                             \e
+        const struct sockaddr_in *:       (t) (p),     \e
+        const struct sockaddr_in6 *:      (t) (p),     \e
+        const struct sockaddr_un *:       (t) (p),     \e
+        default:                              (p)),    \e
+                                                       \e
+    struct sockaddr_in *:                              \e
+        _Generic((typeof_unqual(t)) NULL,              \e
+        struct sockaddr *:                (t) (p),     \e
+        default:                              (p)),    \e
+    struct sockaddr_in **:                             \e
+        _Generic((typeof_unqual(t)) NULL,              \e
+        struct sockaddr **:               (t) (p),     \e
+        default:                              (p)),    \e
+    const struct sockaddr_in *:                        \e
+        _Generic((t) NULL,                             \e
+        const struct sockaddr *:          (t) (p),     \e
+        default:                              (p)),    \e
+                                                       \e
+    struct sockaddr_in6 *:                             \e
+        _Generic((typeof_unqual(t)) NULL,              \e
+        struct sockaddr *:                (t) (p),     \e
+        default:                              (p)),    \e
+    struct sockaddr_in6 **:                            \e
+        _Generic((typeof_unqual(t)) NULL,              \e
+        struct sockaddr **:               (t) (p),     \e
+        default:                              (p)),    \e
+    const struct sockaddr_in6 *:                       \e
+        _Generic((t) NULL,                             \e
+        const struct sockaddr *:          (t) (p),     \e
+        default:                              (p)),    \e
+                                                       \e
+    struct sockaddr_un *:                              \e
+        _Generic((typeof_unqual(t)) NULL,              \e
+        struct sockaddr *:                (t) (p),     \e
+        default:                              (p)),    \e
+    struct sockaddr_un **:                             \e
+        _Generic((typeof_unqual(t)) NULL,              \e
+        struct sockaddr **:               (t) (p),     \e
+        default:                              (p)),    \e
+    const struct sockaddr_un *:                        \e
+        _Generic((t) NULL,                             \e
+        const struct sockaddr *:          (t) (p),     \e
+        default:                              (p)),    \e
+                                                       \e
+    default:                                           \e
+        (p)                                            \e
+    )
+
+socklen_t           slen;
+struct sockaddr_un  sun;
+
+slen = sizeof(ss);
+getsockname(sfd, sockaddr_cast(struct sockaddr *, &sun), &slen);
+.EE
+.PP
 The following program demonstrates how to write
 a replacement for the standard
 .BR imaxabs (3)
 function, which being a function can't really provide what it promises:
 seamlessly upgrading to the widest available type.
-.PP
+.IP
 .\" SRC BEGIN (_Generic.c)
 .EX
 #include <stdint.h>