diff --git a/Makefile b/Makefile
index 68347074..0ab69f31 100644
--- a/Makefile
+++ b/Makefile
@@ -59,7 +59,9 @@ WARNFLAGS=-Wall -Wextra -Wno-unused-parameter
 # -Wformat-nonliteral: If -Wformat is specified, also warn if the format string is not a string literal and so cannot be checked, unless the format function takes its format arguments as a va_list.
 # -Wuninitialized: Warn if an automatic variable is used without first being initialized
 # -Wswitch-enum: Warn whenever a switch statement has an index of enumerated type and lacks a case for one or more of the named codes of that enumeration.
-EXTRAWARN=-Werror -Waddress -Wlogical-op -Wmissing-field-initializers -Woverlength-strings -Wformat -Wformat-nonliteral -Wuninitialized -Wswitch-enum
+# ATTRIBUTEWARNINGS: Warn for cases where adding an attribute may be beneficial.
+ATTRIBUTEWARNINGS= -Wsuggest-attribute=pure -Wsuggest-attribute=const -Wsuggest-attribute=noreturn -Wmissing-noreturn -Wsuggest-attribute=malloc -Wsuggest-attribute=format -Wmissing-format-attribute -Wsuggest-attribute=cold
+EXTRAWARN=-Werror -Waddress -Wlogical-op -Wmissing-field-initializers -Woverlength-strings -Wformat -Wformat-nonliteral -Wuninitialized -Wswitch-enum $(ATTRIBUTEWARNINGS)
 # -FILE_OFFSET_BITS=64: used by stat(). Avoids problems with files > 2 GB on 32bit machines
 CCFLAGS=-std=gnu11 -I$(IDIR) $(WARNFLAGS) -D_FILE_OFFSET_BITS=64 $(HARDENING_FLAGS) $(DEBUG_FLAGS) $(CFLAGS) $(SQLITEFLAGS)
 # for FTL we need the pthread library
diff --git a/api.c b/api.c
index b5e87f03..02d123c2 100644
--- a/api.c
+++ b/api.c
@@ -17,7 +17,7 @@
 #define min(a,b) ({ __typeof__ (a) _a = (a); __typeof__ (b) _b = (b); _a < _b ? _a : _b; })
 
 /* qsort comparision function (count field), sort ASC */
-int cmpasc(const void *a, const void *b)
+static int __attribute__((pure)) cmpasc(const void *a, const void *b)
 {
 	int *elem1 = (int*)a;
 	int *elem2 = (int*)b;
@@ -31,7 +31,7 @@ int cmpasc(const void *a, const void *b)
 }
 
 // qsort subroutine, sort DESC
-int cmpdesc(const void *a, const void *b)
+static int __attribute__((pure)) cmpdesc(const void *a, const void *b)
 {
 	int *elem1 = (int*)a;
 	int *elem2 = (int*)b;
@@ -147,7 +147,7 @@ void getOverTime(int *sock)
 	{
 		for(i = from; i < until; i++)
 		{
-			ssend(*sock,"%i %i %i\n",overTime[i].timestamp,overTime[i].total,overTime[i].blocked);
+			ssend(*sock,"%li %i %i\n",overTime[i].timestamp,overTime[i].total,overTime[i].blocked);
 		}
 	}
 	else
@@ -812,7 +812,7 @@ void getAllQueries(char *client_message, int *sock)
 
 		if(istelnet[*sock])
 		{
-			ssend(*sock,"%i %s %s %s %i %i %i %lu\n",queries[i].timestamp,qtype,domain,client,queries[i].status,queries[i].dnssec,queries[i].reply,delay);
+			ssend(*sock,"%li %s %s %s %i %i %i %lu\n",queries[i].timestamp,qtype,domain,client,queries[i].status,queries[i].dnssec,queries[i].reply,delay);
 		}
 		else
 		{
@@ -926,7 +926,7 @@ void getQueryTypesOverTime(int *sock)
 		}
 
 		if(istelnet[*sock])
-			ssend(*sock, "%i %.2f %.2f\n", overTime[i].timestamp, percentageIPv4, percentageIPv6);
+			ssend(*sock, "%li %.2f %.2f\n", overTime[i].timestamp, percentageIPv4, percentageIPv6);
 		else {
 			pack_int32(*sock, overTime[i].timestamp);
 			pack_float(*sock, percentageIPv4);
@@ -1069,7 +1069,7 @@ void getClientsOverTime(int *sock)
 	for(i = sendit; i < until; i++)
 	{
 		if(istelnet[*sock])
-			ssend(*sock, "%i", overTime[i].timestamp);
+			ssend(*sock, "%li", overTime[i].timestamp);
 		else
 			pack_int32(*sock, overTime[i].timestamp);
 
@@ -1180,7 +1180,7 @@ void getUnknownQueries(int *sock)
 		char *client = getstr(clients[queries[i].clientID].ippos);
 
 		if(istelnet[*sock])
-			ssend(*sock, "%i %i %i %s %s %s %i %s\n", queries[i].timestamp, i, queries[i].id, type, getstr(domains[queries[i].domainID].domainpos), client, queries[i].status, queries[i].complete ? "true" : "false");
+			ssend(*sock, "%li %i %i %s %s %s %i %s\n", queries[i].timestamp, i, queries[i].id, type, getstr(domains[queries[i].domainID].domainpos), client, queries[i].status, queries[i].complete ? "true" : "false");
 		else {
 			pack_int32(*sock, queries[i].timestamp);
 			pack_int32(*sock, queries[i].id);
diff --git a/config.c b/config.c
index 500806cc..108c743b 100644
--- a/config.c
+++ b/config.c
@@ -112,7 +112,7 @@ void read_FTLconf(void)
 			config.maxDBdays = value;
 
 	if(config.maxDBdays == 0)
-		logg("   MAXDBDAYS: --- (DB disabled)", config.maxDBdays);
+		logg("   MAXDBDAYS: --- (DB disabled)");
 	else
 		logg("   MAXDBDAYS: max age for stored queries is %i days", config.maxDBdays);
 
diff --git a/database.c b/database.c
index 7488b2b8..89fe0dc8 100644
--- a/database.c
+++ b/database.c
@@ -681,7 +681,7 @@ void read_data_from_DB(void)
 		return;
 	}
 	// Log DB query string in debug mode
-	if(config.debug & DEBUG_DATABASE) logg(rstr);
+	if(config.debug & DEBUG_DATABASE) logg("%s", rstr);
 
 	// Prepare SQLite3 statement
 	sqlite3_stmt* stmt;
@@ -701,12 +701,12 @@ void read_data_from_DB(void)
 		// 1483228800 = 01/01/2017 @ 12:00am (UTC)
 		if(queryTimeStamp < 1483228800)
 		{
-			logg("DB warn: TIMESTAMP should be larger than 01/01/2017 but is %i", queryTimeStamp);
+			logg("DB warn: TIMESTAMP should be larger than 01/01/2017 but is %li", queryTimeStamp);
 			continue;
 		}
 		if(queryTimeStamp > now)
 		{
-			if(config.debug & DEBUG_DATABASE) logg("DB warn: Skipping query logged in the future (%i)", queryTimeStamp);
+			if(config.debug & DEBUG_DATABASE) logg("DB warn: Skipping query logged in the future (%li)", queryTimeStamp);
 			continue;
 		}
 
@@ -733,14 +733,14 @@ void read_data_from_DB(void)
 		const char * domain = (const char *)sqlite3_column_text(stmt, 4);
 		if(domain == NULL)
 		{
-			logg("DB warn: DOMAIN should never be NULL, %i", queryTimeStamp);
+			logg("DB warn: DOMAIN should never be NULL, %li", queryTimeStamp);
 			continue;
 		}
 
 		const char * client = (const char *)sqlite3_column_text(stmt, 5);
 		if(client == NULL)
 		{
-			logg("DB warn: CLIENT should never be NULL, %i", queryTimeStamp);
+			logg("DB warn: CLIENT should never be NULL, %li", queryTimeStamp);
 			continue;
 		}
 
@@ -759,7 +759,7 @@ void read_data_from_DB(void)
 		{
 			if(forwarddest == NULL)
 			{
-				logg("DB warn: FORWARD should not be NULL with status QUERY_FORWARDED, %i", queryTimeStamp);
+				logg("DB warn: FORWARD should not be NULL with status QUERY_FORWARDED, %li", queryTimeStamp);
 				continue;
 			}
 			forwardID = findForwardID(forwarddest, true);
@@ -846,7 +846,7 @@ void read_data_from_DB(void)
 
 			default:
 				logg("Error: Found unknown status %i in long term database!", status);
-				logg("       Timestamp: %i", queryTimeStamp);
+				logg("       Timestamp: %li", queryTimeStamp);
 				logg("       Continuing anyway...");
 				break;
 		}
diff --git a/dnsmasq_interface.c b/dnsmasq_interface.c
index d11d1de9..6972f1c6 100644
--- a/dnsmasq_interface.c
+++ b/dnsmasq_interface.c
@@ -16,7 +16,7 @@
 
 void print_flags(unsigned int flags);
 void save_reply_type(unsigned int flags, int queryID, struct timeval response);
-unsigned long converttimeval(struct timeval time);
+static unsigned long converttimeval(struct timeval time) __attribute__((const));
 static void block_single_domain_regex(char *domain);
 static void detect_blocked_IP(unsigned short flags, char* answer, int queryID);
 static void query_externally_blocked(int i);
@@ -1076,7 +1076,7 @@ void _FTL_forwarding_failed(struct server *server, const char* file, const int l
 	return;
 }
 
-unsigned long converttimeval(struct timeval time)
+static unsigned long __attribute__((const)) converttimeval(struct timeval time)
 {
 	// Convert time from struct timeval into units
 	// of 10*milliseconds
diff --git a/gc.c b/gc.c
index b9857f97..9713ac01 100644
--- a/gc.c
+++ b/gc.c
@@ -46,7 +46,7 @@ void *GC_thread(void *val)
 
 			long int i;
 			int removed = 0;
-			if(config.debug & DEBUG_GC) logg("GC starting, mintime: %u %s", mintime, ctime(&mintime));
+			if(config.debug & DEBUG_GC) logg("GC starting, mintime: %lu %s", mintime, ctime(&mintime));
 
 			// Process all queries
 			for(i=0; i < counters->queries; i++)
diff --git a/log.c b/log.c
index d1bf7b17..5c34a6d5 100644
--- a/log.c
+++ b/log.c
@@ -61,7 +61,7 @@ void get_timestr(char *timestring)
 	sprintf(timestring,"%d-%02d-%02d %02d:%02d:%02d.%03i", tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday, tm.tm_hour, tm.tm_min, tm.tm_sec, millisec);
 }
 
-void logg(const char *format, ...)
+void __attribute__ ((format (gnu_printf, 1, 2))) logg(const char *format, ...)
 {
 	char timestring[32] = "";
 	va_list args;
diff --git a/memory.c b/memory.c
index b57dccef..898eb782 100644
--- a/memory.c
+++ b/memory.c
@@ -166,7 +166,7 @@ char *FTLstrdup(const char *src, const char * file, const char * function, int l
 }
 
 #undef calloc
-void *FTLcalloc(size_t nmemb, size_t size, const char * file, const char * function, int line)
+void* __attribute__((malloc)) FTLcalloc(size_t nmemb, size_t size, const char * file, const char * function, int line)
 {
 	// The FTLcalloc() function allocates memory for an array of nmemb elements
 	// of size bytes each and returns a pointer to the allocated memory. The
@@ -175,7 +175,7 @@ void *FTLcalloc(size_t nmemb, size_t size, const char * file, const char * funct
 	// passed to free().
 	void *ptr = calloc(nmemb, size);
 	if(ptr == NULL)
-		logg("FATAL: Memory allocation (%u x %u) failed in %s() (%s:%i)",
+		logg("FATAL: Memory allocation (%zu x %zu) failed in %s() (%s:%i)",
 		     nmemb, size, function, file, line);
 
 	return ptr;
@@ -196,7 +196,7 @@ void *FTLrealloc(void *ptr_in, size_t size, const char * file, const char * func
 	// done.
 	void *ptr_out = realloc(ptr_in, size);
 	if(ptr_out == NULL)
-		logg("FATAL: Memory reallocation (%p -> %u) failed in %s() (%s:%i)",
+		logg("FATAL: Memory reallocation (%p -> %zu) failed in %s() (%s:%i)",
 		     ptr_in, size, function, file, line);
 
 	return ptr_out;
diff --git a/msgpack.c b/msgpack.c
index 0f512234..536749e8 100644
--- a/msgpack.c
+++ b/msgpack.c
@@ -22,7 +22,7 @@ void pack_basic(int sock, uint8_t format, void *value, size_t size) {
 	swrite(sock, value, size);
 }
 
-uint64_t leToBe64(uint64_t value) {
+static uint64_t __attribute__((const)) leToBe64(uint64_t value) {
 	char *ptr = (char *) &value;
 	uint32_t part1, part2;
 
diff --git a/overTime.c b/overTime.c
index 29ab2ee6..207d0964 100644
--- a/overTime.c
+++ b/overTime.c
@@ -20,7 +20,7 @@ static void initSlot(unsigned int index, time_t timestamp)
 {
 	// Possible debug printing
 	if(config.debug & DEBUG_OVERTIME)
-		logg("initSlot(%u, %u): Zeroing overTIme slot", index, timestamp);
+		logg("initSlot(%u, %lu): Zeroing overTime slot", index, timestamp);
 
 	overTime[index].magic = MAGICBYTE;
 	overTime[index].timestamp = timestamp;
@@ -48,7 +48,7 @@ void initOverTime(void)
 	time_t timestamp = now - now % 3600 + 3600 - (OVERTIME_INTERVAL / 2);
 
 	if(config.debug & DEBUG_OVERTIME)
-		logg("initOverTime(): Initializing %i slots from %u to %u", OVERTIME_SLOTS, timestamp-OVERTIME_SLOTS*OVERTIME_INTERVAL, timestamp);
+		logg("initOverTime(): Initializing %i slots from %lu to %lu", OVERTIME_SLOTS, timestamp-OVERTIME_SLOTS*OVERTIME_INTERVAL, timestamp);
 
 	// Iterate over overTime and initialize it
 	for(int i = OVERTIME_SLOTS-1; i >= 0 ; i--)
@@ -75,19 +75,19 @@ unsigned int getOverTimeID(time_t timestamp)
 	// Check bounds manually
 	if(id < 0)
 	{
-		logg("WARN: getOverTimeID(%u): %u is negative: %u", timestamp, id, firstTimestamp);
+		logg("WARN: getOverTimeID(%lu): %u is negative: %lu", timestamp, id, firstTimestamp);
 		// Return first timestamp in case negative timestamp was determined
 		return 0;
 	}
 	else if(id > OVERTIME_SLOTS-1)
 	{
-		logg("WARN: getOverTimeID(%u): %i is too large: %u", timestamp, id, firstTimestamp);
+		logg("WARN: getOverTimeID(%lu): %i is too large: %lu", timestamp, id, firstTimestamp);
 		// Return last timestamp in case a too large timestamp was determined
 		return OVERTIME_SLOTS-1;
 	}
 
 	if(config.debug & DEBUG_OVERTIME)
-		logg("getOverTimeID(%u): %i", timestamp, id);
+		logg("getOverTimeID(%lu): %i", timestamp, id);
 
 	return (unsigned int) id;
 }
@@ -111,7 +111,7 @@ void moveOverTimeMemory(time_t mintime)
 	unsigned int remainingSlots = OVERTIME_SLOTS - moveOverTime;
 
 	if(config.debug & DEBUG_OVERTIME)
-		logg("moveOverTimeMemory(): IS: %u, SHOULD: %u, MOVING: %u", oldestOverTimeIS, oldestOverTimeSHOULD, moveOverTime);
+		logg("moveOverTimeMemory(): IS: %lu, SHOULD: %lu, MOVING: %u", oldestOverTimeIS, oldestOverTimeSHOULD, moveOverTime);
 
 	// Check if the move over amount is valid. This prevents errors if the
 	// function is called before GC is necessary.
diff --git a/regex.c b/regex.c
index 93988740..cfcbdd01 100644
--- a/regex.c
+++ b/regex.c
@@ -47,7 +47,7 @@ static bool init_regex(const char *regexin, int index)
 	return true;
 }
 
-bool in_whitelist(char *domain)
+bool __attribute__((pure)) in_whitelist(char *domain)
 {
 	bool found = false;
 	for(int i=0; i < whitelist.count; i++)
diff --git a/request.c b/request.c
index 0245cbb9..74423e77 100644
--- a/request.c
+++ b/request.c
@@ -12,7 +12,7 @@
 #include "api.h"
 #include "shmem.h"
 
-bool command(char *client_message, const char* cmd) {
+bool __attribute__((pure)) command(char *client_message, const char* cmd) {
 	return strstr(client_message, cmd) != NULL;
 }
 
diff --git a/routines.h b/routines.h
index b97d7676..e9ac64d7 100644
--- a/routines.h
+++ b/routines.h
@@ -17,7 +17,7 @@ char * getUserName(void);
 void removepid(void);
 
 void open_FTL_log(bool test);
-void logg(const char* format, ...);
+void logg(const char* format, ...) __attribute__ ((format (gnu_printf, 1, 2)));
 void logg_struct_resize(const char* str, int to, int step);
 void log_counter_info(void);
 void format_memory_size(char *prefix, unsigned long int bytes, double *formated);
@@ -37,7 +37,7 @@ char *getClientNameString(int queryID);
 void close_telnet_socket(void);
 void close_unix_socket(void);
 void seom(int sock);
-void ssend(int sock, const char *format, ...);
+void ssend(int sock, const char *format, ...) __attribute__ ((format (gnu_printf, 2, 3)));
 void swrite(int sock, void *value, size_t size);
 void *telnet_listening_thread_IPv4(void *args);
 void *telnet_listening_thread_IPv6(void *args);
@@ -47,7 +47,7 @@ bool ipv6_available(void);
 void bind_sockets(void);
 
 void process_request(char *client_message, int *sock);
-bool command(char *client_message, const char* cmd);
+bool command(char *client_message, const char* cmd) __attribute__((pure));
 bool matchesEndpoint(char *client_message, const char *cmd);
 
 // grep.c
@@ -60,12 +60,12 @@ char * read_setupVarsconf(const char * key);
 void getSetupVarsArray(char * input);
 void clearSetupVarsArray(void);
 bool insetupVarsArray(char * str);
-bool getSetupVarsBool(char * input);
+bool getSetupVarsBool(char * input) __attribute__((pure));
 
 void parse_args(int argc, char* argv[]);
 
 // setupVars.c
-char* find_equals(const char* s);
+char* find_equals(const char* s) __attribute__((pure));
 void trim_whitespace(char *string);
 
 // config.c
@@ -93,7 +93,7 @@ int db_query_int(const char*);
 // memory.c
 void memory_check(int which);
 char *FTLstrdup(const char *src, const char *file, const char *function, int line);
-void *FTLcalloc(size_t nmemb, size_t size, const char *file, const char *function, int line);
+void *FTLcalloc(size_t nmemb, size_t size, const char *file, const char *function, int line) __attribute__((malloc));
 void *FTLrealloc(void *ptr_in, size_t size, const char *file, const char *function, int line);
 void FTLfree(void *ptr, const char* file, const char *function, int line);
 void validate_access(const char * name, int pos, bool testmagic, int line, const char * function, const char * file);
@@ -112,7 +112,7 @@ void resolveForwardDestinations(bool onlynew);
 bool match_regex(char *input);
 void free_regex(void);
 void read_regex_from_file(void);
-bool in_whitelist(char *domain);
+bool in_whitelist(char *domain) __attribute__((pure));
 
 // shmem.c
 bool init_shmem(void);
diff --git a/setupVars.c b/setupVars.c
index 7570aeb3..1cc9318c 100644
--- a/setupVars.c
+++ b/setupVars.c
@@ -30,7 +30,7 @@ void check_setupVarsconf(void)
 	}
 }
 
-char* find_equals(const char* s)
+char* __attribute__((pure)) find_equals(const char* s)
 {
 	const char* chars = "=";
 	while (*s && (!chars || !strchr(chars, *s)))
@@ -221,7 +221,7 @@ bool insetupVarsArray(char * str)
 	return false;
 }
 
-bool getSetupVarsBool(char * input)
+bool __attribute__((pure)) getSetupVarsBool(char * input)
 {
 	if((strcmp(input, "true")) == 0)
 		return true;
diff --git a/shmem.c b/shmem.c
index 65494798..a0c8f118 100644
--- a/shmem.c
+++ b/shmem.c
@@ -457,7 +457,7 @@ void delete_shm(SharedMemory *sharedMemory)
 }
 
 // Euclidean algorithm to return greatest common divisor of the numbers
-static size_t gcd(size_t a, size_t b)
+static size_t __attribute__((const)) gcd(size_t a, size_t b)
 {
 	while(b != 0)
 	{
diff --git a/signals.c b/signals.c
index 9855c7a1..a0e39526 100644
--- a/signals.c
+++ b/signals.c
@@ -24,7 +24,7 @@ static void SIGSEGV_handler(int sig, siginfo_t *si, void *unused)
 
 	if(FTLstarttime != 0)
 	{
-		logg("FTL has been running for %i seconds", time(NULL)-FTLstarttime);
+		logg("FTL has been running for %li seconds", time(NULL)-FTLstarttime);
 	}
 	log_FTL_version(true);
 
diff --git a/socket.c b/socket.c
index a7354156..d181a919 100644
--- a/socket.c
+++ b/socket.c
@@ -209,7 +209,7 @@ void seom(int sock)
 		pack_eom(sock);
 }
 
-void ssend(int sock, const char *format, ...)
+void __attribute__ ((format (gnu_printf, 2, 3))) ssend(int sock, const char *format, ...)
 {
 	char *buffer;
 	va_list args;