diff --git a/Makefile.am b/Makefile.am
index 37fde7ed..91ba01bd 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -37,8 +37,8 @@ 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
@@ -48,6 +48,9 @@ endif
 CPPFLAGS += -iquote.
 endif
 
+CFLAGS += -Wno-unused-parameter -Wno-unused-variable -Wno-null-pointer-arithmetic
+CFLAGS += -Wno-format-nonliteral
+
 # Set flags for Solaris.
 if IS_SUNOS
 if IS_GCC
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 5262d670..2035470f 100644
--- a/configure.ac
+++ b/configure.ac
@@ -2,6 +2,7 @@
 
 AC_INIT(tmate-ssh-server, 2.3.0)
 
+AM_SILENT_RULES([yes])
 AC_CONFIG_AUX_DIR(etc)
 AM_INIT_AUTOMAKE([foreign subdir-objects])
 
diff --git a/log.c b/log.c
index 54d88cbb..2299b6db 100644
--- a/log.c
+++ b/log.c
@@ -81,6 +81,7 @@ void init_logging(const char *program_name, bool use_syslog, int log_level)
 }
 
 /* Write a log message. */
+__attribute__((__format__(__printf__, 2, 0)))
 static void
 log_vwrite(int level, const char *msg, va_list ap)
 {
@@ -121,6 +122,7 @@ log_debug(const char *msg, ...)
 }
 
 /* Log a critical error with error string and die. */
+__attribute__((__format__(__printf__, 1, 0)))
 __dead void
 fatal(const char *msg, ...)
 {
@@ -130,11 +132,13 @@ fatal(const char *msg, ...)
 	va_start(ap, msg);
 	if (asprintf(&fmt, "fatal: %s: %s", msg, strerror(errno)) == -1)
 		exit(1);
-	log_vwrite(LOG_CRIT, fmt, ap);
+	msg = fmt;
+	log_vwrite(LOG_CRIT, msg, ap);
 	exit(1);
 }
 
 /* Log a critical error and die. */
+__attribute__((__format__(__printf__, 1, 0)))
 __dead void
 fatalx(const char *msg, ...)
 {
@@ -144,10 +148,12 @@ fatalx(const char *msg, ...)
 	va_start(ap, msg);
 	if (asprintf(&fmt, "fatal: %s", msg) == -1)
 		exit(1);
-	log_vwrite(LOG_CRIT, fmt, ap);
+	msg = fmt;
+	log_vwrite(LOG_CRIT, msg, ap);
 	exit(1);
 }
 
+__attribute__((__format__(__printf__, 2, 0)))
 void tmate_log(int level, const char *msg, ...)
 {
 	char *fmt;
@@ -160,7 +166,8 @@ void tmate_log(int level, const char *msg, ...)
 
 	if (asprintf(&fmt, "(tmate) %s", msg) < 0)
 		exit(1);
-	log_vwrite(level, fmt, ap);
+	msg = fmt;
+	log_vwrite(level, msg, ap);
 	va_end(ap);
 
 	free(fmt);
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/proc.c b/proc.c
index fe489181..a8e754b5 100644
--- a/proc.c
+++ b/proc.c
@@ -100,6 +100,7 @@ proc_event_cb(__unused int fd, short events, void *arg)
 	proc_update_event(peer);
 }
 
+#ifndef TMATE
 static void
 proc_signal_cb(int signo, __unused short events, void *arg)
 {
@@ -107,6 +108,7 @@ proc_signal_cb(int signo, __unused short events, void *arg)
 
 	tp->signalcb(signo);
 }
+#endif
 
 static int
 peer_check_version(struct tmuxpeer *peer, struct imsg *imsg)
diff --git a/session.c b/session.c
index a3d1734d..c59a3def 100644
--- a/session.c
+++ b/session.c
@@ -564,6 +564,7 @@ session_group_index(struct session_group *sg)
 	}
 
 	fatalx("session group not found");
+	for(;;);
 }
 
 /*
diff --git a/tmate-ssh-daemon.c b/tmate-ssh-daemon.c
index 77ecd1fe..8f224a28 100644
--- a/tmate-ssh-daemon.c
+++ b/tmate-ssh-daemon.c
@@ -1,5 +1,6 @@
 #include "tmate.h"
 #include <errno.h>
+#include <signal.h>
 
 struct tmate_session _tmate_session, *tmate_session = &_tmate_session;
 
diff --git a/tmate-ssh-server.c b/tmate-ssh-server.c
index 6624ba70..6bcc871c 100644
--- a/tmate-ssh-server.c
+++ b/tmate-ssh-server.c
@@ -339,10 +339,8 @@ static int get_client_ip_proxy_protocol(int fd, char *dst, size_t len)
 
 	tok_num = 0;
 	for (char *tok = strtok(header, " "); tok; tok = strtok(NULL, " "), tok_num++) {
-		if (tok_num == 1) {
-			strncpy(dst, tok, len);
-			dst[len-1] = '\0';
-		}
+		if (tok_num == 1)
+			strlcpy(dst, tok, len);
 	}
 
 	if (tok_num != 5)
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)
 {