diff --git a/Makefile.am b/Makefile.am
index 2551bce3..3da954ae 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -33,8 +33,8 @@ CFLAGS += -g
 CFLAGS += -Wno-long-long -Wall -W -Wnested-externs -Wformat=2
 CFLAGS += -Wmissing-prototypes -Wstrict-prototypes -Wmissing-declarations
 CFLAGS += -Wwrite-strings -Wshadow -Wpointer-arith -Wsign-compare
-CFLAGS += -Wundef -Wbad-function-cast -Winline -Wcast-align
-CFLAGS += -Wdeclaration-after-statement -Wno-pointer-sign -Wno-attributes
+CFLAGS += -Wundef -Wbad-function-cast -Winline
+CFLAGS += -Wno-pointer-sign -Wno-attributes
 CPPFLAGS += -DDEBUG
 endif
 if IS_COVERAGE
@@ -44,6 +44,9 @@ endif
 CPPFLAGS += -iquote.
 endif
 
+CFLAGS += -Wno-unused-parameter -Wno-unused-variable -Wno-null-pointer-arithmetic
+CFLAGS += -Wno-deprecated-declarations -Wno-format-nonliteral
+
 # Set flags for Solaris.
 if IS_SUNOS
 if IS_GCC
diff --git a/client.c b/client.c
index 456fe793..c587ec0d 100644
--- a/client.c
+++ b/client.c
@@ -241,9 +241,6 @@ int run_headless_command(int argc, const char **argv, int flags, void (*err_call
 		return 0;
 
 	/* error messages land in cfg_causes */
-	extern char		**cfg_causes;
-	extern u_int		  cfg_ncauses;
-
 	int ret = cfg_ncauses ? -1 : 0;
 	for (u_int i = 0; i < cfg_ncauses; i++) {
 		if (err_callback)
diff --git a/compat/b64_ntop.c b/compat/b64_ntop.c
index 2b4dc2d4..fd8930f5 100644
--- a/compat/b64_ntop.c
+++ b/compat/b64_ntop.c
@@ -52,6 +52,8 @@
 #include <stdlib.h>
 #include <string.h>
 
+#include "compat.h"
+
 #define Assert(Cond) if (!(Cond)) abort()
 
 static const char Base64[] =
@@ -122,7 +124,7 @@ static const char Pad64 = '=';
    */
 
 int
-b64_ntop(uint8_t const *src, size_t srclength, char *target, size_t targsize) {
+b64_ntop(const char *src, size_t srclength, char *target, size_t targsize) {
 	size_t datalength = 0;
 	uint8_t input[3];
 	uint8_t output[4];
diff --git a/configure.ac b/configure.ac
index f623cadc..8bdb0686 100644
--- a/configure.ac
+++ b/configure.ac
@@ -2,6 +2,7 @@
 
 AC_INIT(tmate, 2.3.1)
 
+AM_SILENT_RULES([yes])
 AC_CONFIG_AUX_DIR(etc)
 AM_INIT_AUTOMAKE([foreign subdir-objects])
 
diff --git a/log.c b/log.c
index bc798778..12266aa4 100644
--- a/log.c
+++ b/log.c
@@ -98,6 +98,7 @@ log_close(void)
 }
 
 /* Write a log message. */
+__attribute__((__format__(__printf__, 1, 0)))
 static void
 log_vwrite(const char *msg, va_list ap)
 {
@@ -144,6 +145,7 @@ log_emit(int level, const char *msg, ...)
 }
 
 /* Log a critical error with error string and die. */
+__attribute__((__format__(__printf__, 1, 0)))
 __dead void
 fatal(const char *msg, ...)
 {
@@ -153,11 +155,13 @@ fatal(const char *msg, ...)
 	va_start(ap, msg);
 	if (asprintf(&fmt, "fatal: %s: %s", msg, strerror(errno)) == -1)
 		exit(1);
-	log_vwrite(fmt, ap);
+	msg = fmt;
+	log_vwrite(msg, ap);
 	exit(1);
 }
 
 /* Log a critical error and die. */
+__attribute__((__format__(__printf__, 1, 0)))
 __dead void
 fatalx(const char *msg, ...)
 {
@@ -167,6 +171,7 @@ fatalx(const char *msg, ...)
 	va_start(ap, msg);
 	if (asprintf(&fmt, "fatal: %s", msg) == -1)
 		exit(1);
-	log_vwrite(fmt, ap);
+	msg = fmt;
+	log_vwrite(msg, ap);
 	exit(1);
 }
diff --git a/osdep-darwin.c b/osdep-darwin.c
index 40b18951..53b48138 100644
--- a/osdep-darwin.c
+++ b/osdep-darwin.c
@@ -28,7 +28,9 @@ char			*osdep_get_name(int, char *);
 char			*osdep_get_cwd(int);
 struct event_base	*osdep_event_init(void);
 
+#ifndef __unused
 #define __unused __attribute__ ((__unused__))
+#endif
 
 char *
 osdep_get_name(int fd, __unused char *tty)
diff --git a/screen-redraw.c b/screen-redraw.c
index 952a8515..4201b022 100644
--- a/screen-redraw.c
+++ b/screen-redraw.c
@@ -278,7 +278,7 @@ screen_redraw_draw_borders(struct client *c, int status, u_int top)
 	struct window		*w = s->curw->window;
 	struct options		*oo = w->options;
 	struct tty		*tty = &c->tty;
-	struct window_pane	*wp;
+	struct window_pane	*wp = NULL;
 	struct grid_cell	 m_active_gc, active_gc, m_other_gc, other_gc;
 	struct grid_cell	 msg_gc;
 	u_int		 	 i, j, type, msgx = 0, msgy = 0;
diff --git a/session.c b/session.c
index d1a644d5..07ca9acc 100644
--- a/session.c
+++ b/session.c
@@ -621,6 +621,7 @@ session_group_index(struct session_group *sg)
 	}
 
 	fatalx("session group not found");
+	for(;;);
 }
 
 /*
diff --git a/tmate-session.c b/tmate-session.c
index 0e6080e8..f3a904bd 100644
--- a/tmate-session.c
+++ b/tmate-session.c
@@ -137,7 +137,7 @@ void tmate_session_init(struct event_base *base)
 	tmate_write_header();
 }
 
-static void send_authorized_keys()
+static void send_authorized_keys(void)
 {
 	char *path;
 	path = options_get_string(global_options, "tmate-authorized-keys");
diff --git a/tmate-ssh-client.c b/tmate-ssh-client.c
index 3f4690df..030b330a 100644
--- a/tmate-ssh-client.c
+++ b/tmate-ssh-client.c
@@ -115,7 +115,7 @@ static int passphrase_callback(__unused const char *prompt, char *buf, size_t le
 	client->tmate_session->need_passphrase = 1;
 
 	if (client->tmate_session->passphrase)
-		strncpy(buf, client->tmate_session->passphrase, len);
+		strlcpy(buf, client->tmate_session->passphrase, len);
 	else
 		strcpy(buf, "");
 
@@ -268,7 +268,7 @@ static void on_ssh_client_event(struct tmate_ssh_client *client)
 		}
 
 		client->state = SSH_CONNECT;
-		/* fall through */
+		// fall through
 
 	case SSH_CONNECT:
 		switch (ssh_connect(session)) {
@@ -284,8 +284,8 @@ static void on_ssh_client_event(struct tmate_ssh_client *client)
 
 			tmate_debug("Establishing connection to %s", client->server_ip);
 			client->state = SSH_AUTH_SERVER;
-			/* fall through */
 		}
+		// fall through
 
 	case SSH_AUTH_SERVER:
 #if LIBSSH_VERSION_INT >= SSH_VERSION_INT(0, 9, 0)
@@ -352,7 +352,7 @@ static void on_ssh_client_event(struct tmate_ssh_client *client)
 		on_ssh_auth_server_complete(client);
 
 		client->state = SSH_AUTH_CLIENT_NONE;
-		/* fall through */
+		// fall through
 
 	case SSH_AUTH_CLIENT_NONE:
 		switch (ssh_userauth_none(session, NULL)) {
@@ -368,8 +368,8 @@ static void on_ssh_client_event(struct tmate_ssh_client *client)
 		case SSH_AUTH_PARTIAL:
 		case SSH_AUTH_DENIED:
 			client->state = SSH_AUTH_CLIENT_PUBKEY;
-			/* fall through */
 		}
+		// fall through
 
 	case SSH_AUTH_CLIENT_PUBKEY:
 		client->tried_passphrase = client->tmate_session->passphrase;
@@ -397,8 +397,8 @@ static void on_ssh_client_event(struct tmate_ssh_client *client)
 		case SSH_AUTH_SUCCESS:
 			tmate_debug("Auth successful with pubkey");
 			client->state = SSH_NEW_CHANNEL;
-			/* fall through */
 		}
+		// fall through
 
 SSH_NEW_CHANNEL:
 	case SSH_NEW_CHANNEL:
@@ -408,6 +408,7 @@ SSH_NEW_CHANNEL:
 			return;
 		}
 		client->state = SSH_OPEN_CHANNEL;
+		// fall through
 
 	case SSH_OPEN_CHANNEL:
 		switch (ssh_channel_open_session(channel)) {
@@ -420,8 +421,8 @@ SSH_NEW_CHANNEL:
 		case SSH_OK:
 			tmate_debug("Session opened, initalizing tmate");
 			client->state = SSH_BOOTSTRAP;
-			/* fall through */
 		}
+		// fall through
 
 	case SSH_BOOTSTRAP:
 		switch (ssh_channel_request_subsystem(channel, "tmate")) {
@@ -449,9 +450,8 @@ SSH_NEW_CHANNEL:
 
 			free(client->tmate_session->last_server_ip);
 			client->tmate_session->last_server_ip = xstrdup(client->server_ip);
-
-			/* fall through */
 		}
+		// fall through
 
 	case SSH_READY:
 		read_channel(client);
diff --git a/tmux.h b/tmux.h
index 9f3ca7bd..c60a044e 100644
--- a/tmux.h
+++ b/tmux.h
@@ -1576,6 +1576,8 @@ void	proc_kill_peer(struct tmuxpeer *);
 extern int cfg_finished;
 extern int cfg_references;
 extern struct client *cfg_client;
+extern char		**cfg_causes;
+extern u_int		  cfg_ncauses;
 void		 start_cfg(void);
 int		 load_cfg(const char *, struct cmd_q *, char **);
 void		 set_cfg_file(const char *);
diff --git a/xmalloc.c b/xmalloc.c
index afa8e585..90af1e2f 100644
--- a/xmalloc.c
+++ b/xmalloc.c
@@ -94,6 +94,7 @@ xasprintf(char **ret, const char *fmt, ...)
 	return i;
 }
 
+__attribute__((__format__(__printf__, 2, 0)))
 int
 xvasprintf(char **ret, const char *fmt, va_list ap)
 {
@@ -120,6 +121,7 @@ xsnprintf(char *str, size_t len, const char *fmt, ...)
 	return i;
 }
 
+__attribute__((__format__(__printf__, 3, 0)))
 int
 xvsnprintf(char *str, size_t len, const char *fmt, va_list ap)
 {