https://github.com/tmux/tmux/pull/3332

From 1b4c87de0249242309f10684761698aa880b80a5 Mon Sep 17 00:00:00 2001
From: Marvin Schmidt <marv@exherbo.org>
Date: Tue, 13 Sep 2022 03:25:00 +0200
Subject: [PATCH 1/2] compat/systemd: Include <string.h> for strerror

Recent compilers are getting stricter about function declarations being
known during compilation and e.g. clang-15 now errors out if a function
signature is not found:

> compat/systemd.c:56:49: error: call to undeclared library function 'strerror' with type 'char *(int)'; ISO C99 and
>       later do not support implicit function declarations [-Wimplicit-function-declaration]
>                 xasprintf(cause, "systemd socket error (%s)", strerror(errno));
>                                                               ^
> compat/systemd.c:56:49: note: include the header <string.h> or explicitly provide a declaration for 'strerror'
> 1 warning and 1 error generated.

Provide the declaration of `strerror` by including `<string.h>` to fix
this
--- a/compat/systemd.c
+++ b/compat/systemd.c
@@ -16,6 +16,7 @@
  * OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  */
 
+#include <string.h>
 #include <sys/types.h>
 #include <sys/un.h>
 

From 1e7ef02c52f2f8a67ab05d8a1c3fec9f4ccb7ea0 Mon Sep 17 00:00:00 2001
From: Marvin Schmidt <marv@exherbo.org>
Date: Tue, 13 Sep 2022 03:34:01 +0200
Subject: [PATCH 2/2] compat/systemd: Use socklen_t instead of int to fix
 warning

clang-15 warns about the pointer passed to `getsockname()` being of
different signedness then the parameter declaration:

> compat/systemd.c:46:47: warning: passing 'int *' to parameter of type 'socklen_t *' (aka 'unsigned int *')
>       converts between pointers to integer types with different sign [-Wpointer-sign]
>                 if (getsockname(fd, (struct sockaddr *)&sa, &addrlen) == -1)
>                                                             ^~~~~~~~
> /usr/x86_64-pc-linux-musl/include/sys/socket.h:391:73: note: passing argument to parameter here
> int getsockname (int, struct sockaddr *__restrict, socklen_t *__restrict);
>                                                                         ^
--- a/compat/systemd.c
+++ b/compat/systemd.c
@@ -30,7 +30,7 @@ systemd_create_socket(int flags, char **cause)
 	int			fds;
 	int			fd;
 	struct sockaddr_un	sa;
-	int			addrlen = sizeof sa;
+	socklen_t		addrlen = sizeof sa;
 
 	fds = sd_listen_fds(0);
 	if (fds > 1) { /* too many file descriptors */