diff --git a/examples/dctool.c b/examples/dctool.c
index ddcd596..3104bc4 100644
--- a/examples/dctool.c
+++ b/examples/dctool.c
@@ -240,7 +240,8 @@ main (int argc, char *argv[])
 	}
 
 	// Translate the help option into a command.
-	char *argv_help[] = {(char *) "help", NULL, NULL};
+	char helpcmd[] = "help";
+	char *argv_help[] = {helpcmd, NULL, NULL};
 	if (help || argv[0] == NULL) {
 		if (argv[0]) {
 			argv_help[1] = argv[0];
diff --git a/examples/dctool_parse.c b/examples/dctool_parse.c
index 6ea8550..6b7da08 100644
--- a/examples/dctool_parse.c
+++ b/examples/dctool_parse.c
@@ -152,7 +152,7 @@ dctool_parse_run (int argc, char *argv[], dc_context_t *context, dc_descriptor_t
 		goto cleanup;
 	}
 
-	for (unsigned int i = 0; i < argc; ++i) {
+	for (int i = 0; i < argc; ++i) {
 		// Read the input file.
 		buffer = dctool_file_read (argv[i]);
 		if (buffer == NULL) {
diff --git a/examples/output_raw.c b/examples/output_raw.c
index 951531e..9e71780 100644
--- a/examples/output_raw.c
+++ b/examples/output_raw.c
@@ -80,7 +80,7 @@ mktemplate_datetime (char *buffer, size_t size, dc_parser_t *parser)
 	n = snprintf (buffer, size, "%04i%02i%02iT%02i%02i%02i",
 		datetime.year, datetime.month, datetime.day,
 		datetime.hour, datetime.minute, datetime.second);
-	if (n < 0 || n >= size)
+	if (n < 0 || (size_t) n >= size)
 		return -1;
 
 	return n;
@@ -92,7 +92,7 @@ mktemplate_number (char *buffer, size_t size, unsigned int number)
 	int n = 0;
 
 	n = snprintf (buffer, size, "%04u", number);
-	if (n < 0 || n >= size)
+	if (n < 0 || (size_t) n >= size)
 		return -1;
 
 	return n;
diff --git a/include/libdivecomputer/datetime.h b/include/libdivecomputer/datetime.h
index 768883d..e5b876f 100644
--- a/include/libdivecomputer/datetime.h
+++ b/include/libdivecomputer/datetime.h
@@ -22,11 +22,13 @@
 #ifndef DC_DATETIME_H
 #define DC_DATETIME_H
 
+#include <limits.h>
+
 #ifdef __cplusplus
 extern "C" {
 #endif /* __cplusplus */
 
-#define DC_TIMEZONE_NONE 0x80000000
+#define DC_TIMEZONE_NONE INT_MIN
 
 #if defined (_WIN32) && !defined (__GNUC__)
 typedef __int64 dc_ticks_t;
diff --git a/src/cochran_commander.c b/src/cochran_commander.c
index 63a00ba..e3677e9 100644
--- a/src/cochran_commander.c
+++ b/src/cochran_commander.c
@@ -41,6 +41,8 @@
 #define COCHRAN_MODEL_EMC_16 4
 #define COCHRAN_MODEL_EMC_20 5
 
+#define UNDEFINED 0xFFFFFFFF
+
 typedef enum cochran_endian_t {
 	ENDIAN_LE,
 	ENDIAN_BE,
@@ -57,8 +59,8 @@ typedef struct cochran_data_t {
 	unsigned char *logbook;
 
 	unsigned short int dive_count;
-	int fp_dive_num;
-	int invalid_profile_dive_num;
+	unsigned int fp_dive_num;
+	unsigned int invalid_profile_dive_num;
 
 	unsigned int logbook_size;
 } cochran_data_t;
@@ -621,18 +623,17 @@ cochran_commander_find_fingerprint(cochran_commander_device_t *device, cochran_d
 	// We track profile ringbuffer usage to determine which dives have profile data
 	int profile_capacity_remaining = device->layout->rb_profile_end - device->layout->rb_profile_begin;
 
-	int dive_count = -1;
-	data->fp_dive_num = -1;
+	unsigned int dive_count = 0;
+	data->fp_dive_num = UNDEFINED;
 
 	// Start at end of log
 	if (data->dive_count < device->layout->rb_logbook_entry_count)
 		dive_count = data->dive_count;
 	else
 		dive_count = device->layout->rb_logbook_entry_count;
-	dive_count--;
 
 	unsigned int sample_read_size = 0;
-	data->invalid_profile_dive_num = -1;
+	data->invalid_profile_dive_num = UNDEFINED;
 
 	// Remove the pre-dive events that occur after the last dive
 	unsigned int rb_head_ptr = 0;
@@ -676,7 +677,7 @@ cochran_commander_find_fingerprint(cochran_commander_device_t *device, cochran_d
 
 	// Loop through dives to find FP, Accumulate profile data size,
 	// and find the last dive with invalid profile
-	for (unsigned int i = 0; i <= dive_count; ++i) {
+	for (unsigned int i = 0; i < dive_count; ++i) {
 		unsigned int idx = (device->layout->rb_logbook_entry_count + head_dive - (i + 1)) % device->layout->rb_logbook_entry_count;
 
 		unsigned char *log_entry = data->logbook + idx * device->layout->rb_logbook_entry_size;
@@ -953,7 +954,7 @@ cochran_commander_device_foreach (dc_device_t *abstract, dc_dive_callback_t call
 	}
 
 	// Change tail to dive following the fingerprint dive.
-	if (data.fp_dive_num > -1)
+	if (data.fp_dive_num != UNDEFINED)
 		tail_dive = (data.fp_dive_num + 1) % layout->rb_logbook_entry_count;
 
 	// Number of dives to read
diff --git a/src/context.c b/src/context.c
index c7642e6..21c1610 100644
--- a/src/context.c
+++ b/src/context.c
@@ -27,6 +27,7 @@
 #include <stdio.h>
 #include <stdarg.h>
 #include <string.h>
+#include <limits.h>
 
 #ifdef _WIN32
 #define WIN32_LEAN_AND_MEAN
@@ -77,7 +78,7 @@ l_vsnprintf (char *str, size_t size, const char *format, va_list ap)
 	 * enough.
 	 */
 	n = vsnprintf (str, size, format, ap);
-	if (n >= size)
+	if (n >= 0 && (size_t) n >= size)
 		n = -1;
 #endif
 
@@ -104,7 +105,7 @@ l_hexdump (char *str, size_t size, const unsigned char data[], size_t n)
 		'0', '1', '2', '3', '4', '5', '6', '7',
 		'8', '9', 'A', 'B', 'C', 'D', 'E', 'F'};
 
-	if (size == 0)
+	if (size == 0 || size > INT_MAX)
 		return -1;
 
 	/* The maximum number of bytes. */
@@ -126,11 +127,11 @@ l_hexdump (char *str, size_t size, const unsigned char data[], size_t n)
 	/* Null terminate the hex string. */
 	str[length * 2] = 0;
 
-	return (n > maxlength ? -1 : length * 2);
+	return (n > maxlength ? -1 : (int) (length * 2));
 }
 
 static void
-logfunc (dc_context_t *context, dc_loglevel_t loglevel, const char *file, unsigned int line, const char *function, const char *msg, void *userdata)
+loghandler (dc_context_t *context, dc_loglevel_t loglevel, const char *file, unsigned int line, const char *function, const char *msg, void *userdata)
 {
 	const char *loglevels[] = {"NONE", "ERROR", "WARNING", "INFO", "DEBUG", "ALL"};
 
@@ -166,7 +167,7 @@ dc_context_new (dc_context_t **out)
 
 #ifdef ENABLE_LOGGING
 	context->loglevel = DC_LOGLEVEL_WARNING;
-	context->logfunc = logfunc;
+	context->logfunc = loghandler;
 #else
 	context->loglevel = DC_LOGLEVEL_NONE;
 	context->logfunc = NULL;
diff --git a/src/hw_ostc3.c b/src/hw_ostc3.c
index c669ea2..3ed6bc7 100644
--- a/src/hw_ostc3.c
+++ b/src/hw_ostc3.c
@@ -1024,7 +1024,7 @@ hw_ostc3_firmware_readline (FILE *fp, dc_context_t *context, unsigned int addr,
 	unsigned char ascii[39];
 	unsigned char faddr_byte[3];
 	unsigned int faddr = 0;
-	int n = 0;
+	size_t n = 0;
 
 	if (size > 16) {
 		ERROR (context, "Invalid arguments.");
diff --git a/src/hw_ostc_parser.c b/src/hw_ostc_parser.c
index 117064b..714318b 100644
--- a/src/hw_ostc_parser.c
+++ b/src/hw_ostc_parser.c
@@ -390,7 +390,6 @@ hw_ostc_parser_get_datetime (dc_parser_t *abstract, dc_datetime_t *datetime)
 {
 	hw_ostc_parser_t *parser = (hw_ostc_parser_t *) abstract;
 	const unsigned char *data = abstract->data;
-	unsigned int size = abstract->size;
 
 	// Cache the header data.
 	dc_status_t rc = hw_ostc_parser_cache (parser);
@@ -451,7 +450,6 @@ hw_ostc_parser_get_field (dc_parser_t *abstract, dc_field_type_t type, unsigned
 {
 	hw_ostc_parser_t *parser = (hw_ostc_parser_t *) abstract;
 	const unsigned char *data = abstract->data;
-	unsigned int size = abstract->size;
 
 	// Cache the header data.
 	dc_status_t rc = hw_ostc_parser_cache (parser);
diff --git a/src/irda.c b/src/irda.c
index 448c57c..2cc58ab 100644
--- a/src/irda.c
+++ b/src/irda.c
@@ -155,7 +155,7 @@ dc_irda_iterator_new (dc_iterator_t **out, dc_context_t *context, dc_descriptor_
 	}
 
 	// Open the socket.
-	int fd = socket (AF_IRDA, SOCK_STREAM, 0);
+	s_socket_t fd = socket (AF_IRDA, SOCK_STREAM, 0);
 	if (fd == S_INVALID) {
 		s_errcode_t errcode = S_ERRNO;
 		SYSERROR (context, errcode);
diff --git a/src/oceanic_atom2_parser.c b/src/oceanic_atom2_parser.c
index e2a54ff..9ddb1d4 100644
--- a/src/oceanic_atom2_parser.c
+++ b/src/oceanic_atom2_parser.c
@@ -527,9 +527,7 @@ oceanic_atom2_parser_get_field (dc_parser_t *abstract, dc_field_type_t type, uns
 {
 	dc_status_t status = DC_STATUS_SUCCESS;
 	oceanic_atom2_parser_t *parser = (oceanic_atom2_parser_t *) abstract;
-
 	const unsigned char *data = abstract->data;
-	unsigned int size = abstract->size;
 
 	// Cache the header data.
 	status = oceanic_atom2_parser_cache (parser);
diff --git a/src/oceanic_vtpro.c b/src/oceanic_vtpro.c
index 22d61fd..74b94ec 100644
--- a/src/oceanic_vtpro.c
+++ b/src/oceanic_vtpro.c
@@ -592,8 +592,8 @@ oceanic_vtpro_device_version (dc_device_t *abstract, unsigned char data[], unsig
 				return rc;
 
 			// Verify the checksum of the answer.
-			unsigned char crc = answer[PAGESIZE / 2];
-			unsigned char ccrc = checksum_add_uint4 (answer, PAGESIZE / 2, 0x00);
+			crc = answer[PAGESIZE / 2];
+			ccrc = checksum_add_uint4 (answer, PAGESIZE / 2, 0x00);
 			if (crc != ccrc) {
 				ERROR (abstract->context, "Unexpected answer checksum.");
 				return DC_STATUS_PROTOCOL;
diff --git a/src/reefnet_sensuspro_parser.c b/src/reefnet_sensuspro_parser.c
index fe62668..7e68a72 100644
--- a/src/reefnet_sensuspro_parser.c
+++ b/src/reefnet_sensuspro_parser.c
@@ -163,8 +163,8 @@ reefnet_sensuspro_parser_get_field (dc_parser_t *abstract, dc_field_type_t type,
 		while (offset + sizeof (footer) <= size &&
 			memcmp (data + offset, footer, sizeof (footer)) != 0)
 		{
-			unsigned int value = array_uint16_le (data + offset);
-			unsigned int depth = (value & 0x01FF);
+			unsigned int raw = array_uint16_le (data + offset);
+			unsigned int depth = (raw & 0x01FF);
 			if (depth > maxdepth)
 				maxdepth = depth;
 
diff --git a/src/suunto_d9.c b/src/suunto_d9.c
index ab6eee1..8b8320e 100644
--- a/src/suunto_d9.c
+++ b/src/suunto_d9.c
@@ -261,7 +261,8 @@ suunto_d9_device_packet (dc_device_t *abstract, const unsigned char command[], u
 	}
 
 	// Verify the size of the package.
-	if (array_uint16_be (answer + 1) + 4 != asize) {
+	unsigned int len = array_uint16_be (answer + 1);
+	if (len + 4 != asize) {
 		ERROR (abstract->context, "Unexpected answer size.");
 		return DC_STATUS_PROTOCOL;
 	}
diff --git a/src/suunto_d9_parser.c b/src/suunto_d9_parser.c
index 6bf33b8..bd91743 100644
--- a/src/suunto_d9_parser.c
+++ b/src/suunto_d9_parser.c
@@ -348,9 +348,7 @@ static dc_status_t
 suunto_d9_parser_get_field (dc_parser_t *abstract, dc_field_type_t type, unsigned int flags, void *value)
 {
 	suunto_d9_parser_t *parser = (suunto_d9_parser_t*) abstract;
-
 	const unsigned char *data = abstract->data;
-	unsigned int size = abstract->size;
 
 	// Cache the gas mix data.
 	dc_status_t rc = suunto_d9_parser_cache (parser);
diff --git a/src/suunto_eonsteel_parser.c b/src/suunto_eonsteel_parser.c
index 7a4c032..033a2f2 100644
--- a/src/suunto_eonsteel_parser.c
+++ b/src/suunto_eonsteel_parser.c
@@ -95,7 +95,7 @@ typedef struct suunto_eonsteel_parser_t {
 	} cache;
 } suunto_eonsteel_parser_t;
 
-typedef int (*eon_data_cb_t)(unsigned short type, const struct type_desc *desc, const unsigned char *data, int len, void *user);
+typedef int (*eon_data_cb_t)(unsigned short type, const struct type_desc *desc, const unsigned char *data, unsigned int len, void *user);
 
 typedef struct eon_event_t {
 	const char *name;
@@ -137,7 +137,6 @@ static const struct {
 
 static enum eon_sample lookup_descriptor_type(suunto_eonsteel_parser_t *eon, struct type_desc *desc)
 {
-	int i;
 	const char *name = desc->desc;
 
 	// Not a sample type? Skip it
@@ -160,7 +159,7 @@ static enum eon_sample lookup_descriptor_type(suunto_eonsteel_parser_t *eon, str
 	name += 8;
 
 	// .. and look it up in the table of sample type strings
-	for (i = 0; i < C_ARRAY_SIZE(type_translation); i++) {
+	for (size_t i = 0; i < C_ARRAY_SIZE(type_translation); i++) {
 		if (!strcmp(name, type_translation[i].name))
 			return type_translation[i].type;
 	}
@@ -179,8 +178,7 @@ static parser_sample_event_t lookup_event(const char *name, const eon_event_t ev
 
 static const char *desc_type_name(enum eon_sample type)
 {
-	int i;
-	for (i = 0; i < C_ARRAY_SIZE(type_translation); i++) {
+	for (size_t i = 0; i < C_ARRAY_SIZE(type_translation); i++) {
 		if (type == type_translation[i].type)
 			return type_translation[i].name;
 	}
@@ -366,10 +364,10 @@ static int record_type(suunto_eonsteel_parser_t *eon, unsigned short type, const
 	return 0;
 }
 
-static int traverse_entry(suunto_eonsteel_parser_t *eon, const unsigned char *p, int len, eon_data_cb_t callback, void *user)
+static int traverse_entry(suunto_eonsteel_parser_t *eon, const unsigned char *p, int size, eon_data_cb_t callback, void *user)
 {
-	const unsigned char *name, *data, *end, *last, *one_past_end = p + len;
-	int textlen, type;
+	const unsigned char *name, *data, *end, *last, *one_past_end = p + size;
+	int textlen, id;
 	int rc;
 
 	// First two bytes: zero and text length
@@ -388,7 +386,7 @@ static int traverse_entry(suunto_eonsteel_parser_t *eon, const unsigned char *p,
 
 	// Two bytes of 'type' followed by the name/descriptor, followed by the data
 	data = name + textlen;
-	type = array_uint16_le(name);
+	id = array_uint16_le(name);
 	name += 2;
 
 	if (*name != '<') {
@@ -396,7 +394,7 @@ static int traverse_entry(suunto_eonsteel_parser_t *eon, const unsigned char *p,
 		return -1;
 	}
 
-	record_type(eon, type, (const char *) name, textlen-3);
+	record_type(eon, id, (const char *) name, textlen-3);
 
 	end = data;
 	last = data;
@@ -860,7 +858,7 @@ static void sample_setpoint_automatic(struct sample_data *info, unsigned char va
 	DEBUG(info->eon->base.context, "sample_setpoint_automatic(%u)", value);
 }
 
-static int handle_sample_type(const struct type_desc *desc, struct sample_data *info, enum eon_sample type, const unsigned char *data)
+static unsigned int handle_sample_type(const struct type_desc *desc, struct sample_data *info, enum eon_sample type, const unsigned char *data)
 {
 	switch (type) {
 	case ES_dtime:
@@ -968,7 +966,7 @@ static int handle_sample_type(const struct type_desc *desc, struct sample_data *
 	}
 }
 
-static int traverse_samples(unsigned short type, const struct type_desc *desc, const unsigned char *data, int len, void *user)
+static int traverse_samples(unsigned short type, const struct type_desc *desc, const unsigned char *data, unsigned int len, void *user)
 {
 	struct sample_data *info = (struct sample_data *) user;
 	suunto_eonsteel_parser_t *eon = info->eon;
@@ -982,8 +980,7 @@ static int traverse_samples(unsigned short type, const struct type_desc *desc, c
 	info->ceiling = 0.0;
 
 	for (i = 0; i < EON_MAX_GROUP; i++) {
-		enum eon_sample type = desc->type[i];
-		int bytes = handle_sample_type(desc, info, type, data);
+		unsigned int bytes = handle_sample_type(desc, info, desc->type[i], data);
 
 		if (!bytes)
 			break;
@@ -1246,8 +1243,6 @@ static float get_le32_float(const unsigned char *src)
 static int traverse_device_fields(suunto_eonsteel_parser_t *eon, const struct type_desc *desc,
                                   const unsigned char *data, int len)
 {
-	const char *name = desc->desc + strlen("sml.DeviceLog.Device.");
-
 	return 0;
 }
 
@@ -1429,13 +1424,15 @@ static int traverse_sample_fields(suunto_eonsteel_parser_t *eon, const struct ty
 			set_depth_field(eon, array_uint16_le(data));
 			data += 2;
 			continue;
+		default:
+			break;
 		}
 		break;
 	}
 	return 0;
 }
 
-static int traverse_fields(unsigned short type, const struct type_desc *desc, const unsigned char *data, int len, void *user)
+static int traverse_fields(unsigned short type, const struct type_desc *desc, const unsigned char *data, unsigned int len, void *user)
 {
 	suunto_eonsteel_parser_t *eon = (suunto_eonsteel_parser_t *) user;
 
diff --git a/src/suunto_solution_parser.c b/src/suunto_solution_parser.c
index 9b2ac9d..34aab7d 100644
--- a/src/suunto_solution_parser.c
+++ b/src/suunto_solution_parser.c
@@ -110,10 +110,10 @@ suunto_solution_parser_get_field (dc_parser_t *abstract, dc_field_type_t type, u
 		unsigned int depth = 0, maxdepth = 0;
 		unsigned int offset = 3;
 		while (offset < size && data[offset] != 0x80) {
-			unsigned char value = data[offset++];
-			if (value < 0x7e || value > 0x82) {
-				depth += (signed char) value;
-				if (value == 0x7D || value == 0x83) {
+			unsigned char raw = data[offset++];
+			if (raw < 0x7e || raw > 0x82) {
+				depth += (signed char) raw;
+				if (raw == 0x7D || raw == 0x83) {
 					if (offset + 1 > size)
 						return DC_STATUS_DATAFORMAT;
 					depth += (signed char) data[offset++];
diff --git a/src/suunto_vyper2.c b/src/suunto_vyper2.c
index 02f38ed..7a9f7ce 100644
--- a/src/suunto_vyper2.c
+++ b/src/suunto_vyper2.c
@@ -252,7 +252,8 @@ suunto_vyper2_device_packet (dc_device_t *abstract, const unsigned char command[
 	}
 
 	// Verify the size of the package.
-	if (array_uint16_be (answer + 1) + 4 != asize) {
+	unsigned int len = array_uint16_be (answer + 1);
+	if (len + 4 != asize) {
 		ERROR (abstract->context, "Unexpected answer size.");
 		return DC_STATUS_PROTOCOL;
 	}
diff --git a/src/suunto_vyper_parser.c b/src/suunto_vyper_parser.c
index 80f7d54..369ad5c 100644
--- a/src/suunto_vyper_parser.c
+++ b/src/suunto_vyper_parser.c
@@ -234,9 +234,7 @@ static dc_status_t
 suunto_vyper_parser_get_field (dc_parser_t *abstract, dc_field_type_t type, unsigned int flags, void *value)
 {
 	suunto_vyper_parser_t *parser = (suunto_vyper_parser_t *) abstract;
-
 	const unsigned char *data = abstract->data;
-	unsigned int size = abstract->size;
 
 	dc_gasmix_t *gas = (dc_gasmix_t *) value;
 	dc_tank_t *tank = (dc_tank_t *) value;
diff --git a/src/usbhid.c b/src/usbhid.c
index 9231e64..b3805ca 100644
--- a/src/usbhid.c
+++ b/src/usbhid.c
@@ -777,7 +777,7 @@ dc_usbhid_write (dc_iostream_t *abstract, const void *data, size_t size, size_t
 
 out:
 #ifdef _WIN32
-	if (nbytes > size) {
+	if ((size_t) nbytes > size) {
 		WARNING (abstract->context, "Number of bytes exceeds the buffer size (" DC_PRINTF_SIZE " > " DC_PRINTF_SIZE ")!", nbytes, size);
 		nbytes = size;
 	}