diff --git a/core/dive.cpp b/core/dive.cpp
index 7304b5eff..10e98ae6b 100644
--- a/core/dive.cpp
+++ b/core/dive.cpp
@@ -19,6 +19,7 @@
 #include "extradata.h"
 #include "interpolate.h"
 #include "qthelper.h"
+#include "range.h"
 #include "membuffer.h"
 #include "picture.h"
 #include "sample.h"
@@ -174,13 +175,6 @@ int dive_getUniqID()
 	return maxId;
 }
 
-/* copy an element in a list of dive computer extra data */
-static void copy_extra_data(struct extra_data *sed, struct extra_data *ded)
-{
-	ded->key = copy_string(sed->key);
-	ded->value = copy_string(sed->value);
-}
-
 /* this is very different from the copy_dive_computer later in this file;
  * this function actually makes full copies of the content */
 static void copy_dc(const struct divecomputer *sdc, struct divecomputer *ddc)
@@ -188,7 +182,6 @@ static void copy_dc(const struct divecomputer *sdc, struct divecomputer *ddc)
 	*ddc = *sdc;
 	copy_samples(sdc, ddc);
 	copy_events(sdc, ddc);
-	STRUCTURED_LIST_COPY(struct extra_data, sdc->extra_data, ddc->extra_data, copy_extra_data);
 }
 
 static void dc_cylinder_renumber(struct dive *dive, struct divecomputer *dc, const int mapping[]);
@@ -1453,26 +1446,9 @@ static void merge_samples(struct divecomputer *res,
 	}
 }
 
-/*
- * Does the extradata key/value pair already exist in the
- * supplied dive computer data?
- *
- * This is not hugely efficient (with the whole "do this for
- * every value you merge" it's O(n**2)) but it's not like we
- * have very many extra_data entries per dive computer anyway.
- */
-static bool extra_data_exists(const struct extra_data *ed, const struct divecomputer *dc)
+static bool operator==(const struct extra_data &e1, const struct extra_data &e2)
 {
-	const struct extra_data *p;
-
-	for (p = dc->extra_data; p; p = p->next) {
-		if (strcmp(p->key, ed->key))
-			continue;
-		if (strcmp(p->value, ed->value))
-			continue;
-		return true;
-	}
-	return false;
+	return std::tie(e1.key, e1.value) == std::tie(e2.key, e2.value);
 }
 
 /*
@@ -1480,29 +1456,20 @@ static bool extra_data_exists(const struct extra_data *ed, const struct divecomp
  *
  * The extra data from 'a' has already been copied into 'res'. So
  * we really should just copy over the data from 'b' too.
+ *
+ * This is not hugely efficient (with the whole "check this for
+ * every value you merge" it's O(n**2)) but it's not like we
+ * have very many extra_data entries per dive computer anyway.
  */
 static void merge_extra_data(struct divecomputer *res,
 			  const struct divecomputer *a, const struct divecomputer *b)
 {
-	struct extra_data **ed, *src;
-
-	// Find the place to add things in the result
-	ed = &res->extra_data;
-	while (*ed)
-		ed = &(*ed)->next;
-
-	for (src = b->extra_data; src; src = src->next) {
-		if (extra_data_exists(src, a))
+	for (auto &ed: b->extra_data) {
+		if (range_contains(a->extra_data, ed))
 			continue;
-		*ed = (extra_data *)malloc(sizeof(struct extra_data));
-		if (!*ed)
-			break;
-		copy_extra_data(src, *ed);
-		ed = &(*ed)->next;
-	}
 
-	// Terminate the result list
-	*ed = NULL;
+		res->extra_data.push_back(ed);
+	}
 }
 
 static char *merge_text(const char *a, const char *b, const char *sep)
@@ -2449,7 +2416,6 @@ static const struct divecomputer *find_matching_computer(const struct divecomput
 static void copy_dive_computer(struct divecomputer *res, const struct divecomputer *a)
 {
 	*res = *a;
-	STRUCTURED_LIST_COPY(struct extra_data, a->extra_data, res->extra_data, copy_extra_data);
 	res->samples = res->alloc_samples = 0;
 	res->sample = NULL;
 	res->events = NULL;
@@ -3415,19 +3381,19 @@ int dive_has_gps_location(const struct dive *dive)
  * or GPS2 extra data fields */
 static location_t dc_get_gps_location(const struct divecomputer *dc)
 {
-	location_t res = { };
+	location_t res;
 
-	for (struct extra_data *data = dc->extra_data; data; data = data->next) {
-		if (!strcmp(data->key, "GPS1")) {
-			parse_location(data->value, &res);
+	for (const auto &data: dc->extra_data) {
+		if (data.key == "GPS1") {
+			parse_location(data.value.c_str(), &res);
 			/* If we found a valid GPS1 field exit early since
 			 * it has priority over GPS2 */
 			if (has_location(&res))
 				break;
-		} else if (!strcmp(data->key, "GPS2")) {
+		} else if (data.key == "GPS2") {
 			/* For GPS2 fields continue searching, as we might
 			 * still find a GPS1 field */
-			parse_location(data->value, &res);
+			parse_location(data.value.c_str(), &res);
 		}
 	}
 	return res;
diff --git a/core/divecomputer.cpp b/core/divecomputer.cpp
index e42f75654..131758226 100644
--- a/core/divecomputer.cpp
+++ b/core/divecomputer.cpp
@@ -20,6 +20,8 @@ divecomputer::~divecomputer()
 	free_dc_contents(this);
 }
 
+divecomputer::divecomputer(divecomputer &&) = default;
+
 /*
  * Good fake dive profiles are hard.
  *
@@ -483,26 +485,16 @@ void remove_event_from_dc(struct divecomputer *dc, struct event *event)
 	}
 }
 
-void add_extra_data(struct divecomputer *dc, const char *key, const char *value)
+void add_extra_data(struct divecomputer *dc, const std::string &key, const std::string &value)
 {
-	struct extra_data **ed = &dc->extra_data;
-
-	if (!strcasecmp(key, "Serial")) {
-		dc->deviceid = calculate_string_hash(value);
+	if (key == "Serial") {
+		dc->deviceid = calculate_string_hash(value.c_str());
 		dc->serial = value;
 	}
-	if (!strcmp(key, "FW Version")) {
+	if (key == "FW Version")
 		dc->fw_version = value;
-	}
 
-	while (*ed)
-		ed = &(*ed)->next;
-	*ed = (struct extra_data *)malloc(sizeof(struct extra_data));
-	if (*ed) {
-		(*ed)->key = strdup(key);
-		(*ed)->value = strdup(value);
-		(*ed)->next = NULL;
-	}
+	dc->extra_data.push_back(extra_data { key, value });
 }
 
 /*
@@ -534,17 +526,10 @@ int match_one_dc(const struct divecomputer *a, const struct divecomputer *b)
 	return a->diveid == b->diveid && a->when == b->when ? 1 : -1;
 }
 
-static void free_extra_data(struct extra_data *ed)
-{
-	free((void *)ed->key);
-	free((void *)ed->value);
-}
-
 void free_dc_contents(struct divecomputer *dc)
 {
 	free(dc->sample);
 	free_events(dc->events);
-	STRUCTURED_LIST_FREE(struct extra_data, dc->extra_data, free_extra_data);
 }
 
 static const char *planner_dc_name = "planned dive";
diff --git a/core/divecomputer.h b/core/divecomputer.h
index eb1c914bc..1e7240809 100644
--- a/core/divecomputer.h
+++ b/core/divecomputer.h
@@ -5,6 +5,7 @@
 #include "divemode.h"
 #include "units.h"
 #include <string>
+#include <vector>
 
 struct extra_data;
 struct sample;
@@ -39,11 +40,12 @@ struct divecomputer {
 	int samples = 0, alloc_samples = 0;
 	struct sample *sample = nullptr;
 	struct event *events = nullptr;
-	struct extra_data *extra_data = nullptr;
+	std::vector<struct extra_data> extra_data;
 	struct divecomputer *next = nullptr;
 
 	divecomputer();
 	~divecomputer();
+	divecomputer(divecomputer &&);
 };
 
 extern void fake_dc(struct divecomputer *dc);
@@ -65,7 +67,7 @@ extern void copy_samples(const struct divecomputer *s, struct divecomputer *d);
 extern void add_event_to_dc(struct divecomputer *dc, struct event *ev);
 extern struct event *add_event(struct divecomputer *dc, unsigned int time, int type, int flags, int value, const std::string &name);
 extern void remove_event_from_dc(struct divecomputer *dc, struct event *event);
-extern void add_extra_data(struct divecomputer *dc, const char *key, const char *value);
+extern void add_extra_data(struct divecomputer *dc, const std::string &key, const std::string &value);
 extern uint32_t calculate_string_hash(const char *str);
 extern bool is_dc_planner(const struct divecomputer *dc);
 extern void make_planner_dc(struct divecomputer *dc);
diff --git a/core/divelist.cpp b/core/divelist.cpp
index 9cf5023d8..21795f499 100644
--- a/core/divelist.cpp
+++ b/core/divelist.cpp
@@ -616,12 +616,6 @@ void update_cylinder_related_info(struct dive *dive)
 	}
 }
 
-/* Like strcmp(), but don't crash on null-pointers */
-static int safe_strcmp(const char *s1, const char *s2)
-{
-	return strcmp(s1 ? s1 : "", s2 ? s2 : "");
-}
-
 /* Compare a list of dive computers by model name */
 static int comp_dc(const struct divecomputer *dc1, const struct divecomputer *dc2)
 {
diff --git a/core/extradata.h b/core/extradata.h
index 4f9a72f20..d81ad17ad 100644
--- a/core/extradata.h
+++ b/core/extradata.h
@@ -2,10 +2,11 @@
 #ifndef EXTRADATA_H
 #define EXTRADATA_H
 
+#include <string>
+
 struct extra_data {
-	const char *key;
-	const char *value;
-	struct extra_data *next;
+	std::string key;
+	std::string value;
 };
 
 #endif
diff --git a/core/import-csv.cpp b/core/import-csv.cpp
index 6c8208fb5..2d148ed34 100644
--- a/core/import-csv.cpp
+++ b/core/import-csv.cpp
@@ -548,7 +548,7 @@ int parse_txt_file(const char *filename, const char *csv, struct divelog *log)
 			std::string value = parse_mkvi_value(lineptr, key.c_str());
 			if (value.empty())
 				break;
-			add_extra_data(&dive->dc, key.c_str(), value.c_str());
+			add_extra_data(&dive->dc, key, value);
 		}
 		dc = &dive->dc;
 
diff --git a/core/load-git.cpp b/core/load-git.cpp
index 29b3b8aaa..3f892522c 100644
--- a/core/load-git.cpp
+++ b/core/load-git.cpp
@@ -828,7 +828,7 @@ static void parse_dc_keyvalue(char *line, struct git_parser_state *state)
 	if (state->converted_strings.size() != 2)
 		return;
 
-	add_extra_data(state->active_dc, state->converted_strings[0].c_str(), state->converted_strings[1].c_str());
+	add_extra_data(state->active_dc, state->converted_strings[0], state->converted_strings[1]);
 }
 
 static void parse_dc_event(char *line, struct git_parser_state *state)
diff --git a/core/ostctools.cpp b/core/ostctools.cpp
index 4355c0e82..a1ec4bb9d 100644
--- a/core/ostctools.cpp
+++ b/core/ostctools.cpp
@@ -52,7 +52,6 @@ void ostctools_import(const char *file, struct divelog *log)
 	dc_status_t rc = DC_STATUS_SUCCESS;
 	int model, ret, i = 0, c;
 	unsigned int serial;
-	struct extra_data *ptr;
 	const char *failed_to_read_msg = translate("gettextFromC", "Failed to read '%s'");
 
 	// Open the archive
@@ -161,21 +160,16 @@ void ostctools_import(const char *file, struct divelog *log)
 		report_error(translate("gettextFromC", "Error - %s - parsing dive %d"), errmsg(rc), ostcdive->number);
 
 	// Serial number is not part of the header nor the profile, so libdc won't
-	// catch it. If Serial is part of the extra_data, and set to zero, remove
-	// it from the list and add again.
+	// catch it. If Serial is part of the extra_data, and set to zero, replace it.
 	ostcdive->dc.serial = std::to_string(serial);
 
-	if (ostcdive->dc.extra_data) {
-		ptr = ostcdive->dc.extra_data;
-		while (strcmp(ptr->key, "Serial"))
-			ptr = ptr->next;
-		if (!strcmp(ptr->value, "0")) {
-			add_extra_data(&ostcdive->dc, "Serial", ostcdive->dc.serial.c_str());
-			*ptr = *(ptr)->next;
-		}
-	} else {
-		add_extra_data(&ostcdive->dc, "Serial", ostcdive->dc.serial.c_str());
-	}
+	auto it = find_if(ostcdive->dc.extra_data.begin(), ostcdive->dc.extra_data.end(),
+			 [](auto &ed) { return ed.key == "Serial"; });
+	if (it != ostcdive->dc.extra_data.end() && it->value == "0")
+		it->value = ostcdive->dc.serial.c_str();
+	else if (it == ostcdive->dc.extra_data.end())
+		add_extra_data(&ostcdive->dc, "Serial", ostcdive->dc.serial);
+
 	record_dive_to_table(ostcdive.release(), log->dives.get());
 	sort_dive_table(log->dives.get());
 }
diff --git a/core/parse-xml.cpp b/core/parse-xml.cpp
index 9e84bc1ba..4a85a58e0 100644
--- a/core/parse-xml.cpp
+++ b/core/parse-xml.cpp
@@ -2114,20 +2114,21 @@ int parse_dlf_buffer(unsigned char *buffer, size_t size, struct divelog *log)
 			/* device configuration */
 			switch (((ptr[3] & 0x7f) << 3) + ((ptr[2] & 0xe0) >> 5)) {
 				// Buffer to print extra string into
-				char config_buf[256];
 				// Local variables to temporary decode into
 				struct tm tm;
 				const char *device;
 				const char *deep_stops;
 				case 0: // TEST_CCR_FULL_1
 					utc_mkdate(parse_dlf_timestamp(ptr + 12), &tm);
-					snprintf(config_buf, sizeof(config_buf), "START=%04u-%02u-%02u %02u:%02u:%02u,TEST=%02X%02X%02X%02X,RESULT=%02X%02X%02X%02X", tm.tm_year, tm.tm_mon + 1, tm.tm_mday, tm.tm_hour, tm.tm_min, tm.tm_sec, ptr[7], ptr[6], ptr[5], ptr[4], ptr[11], ptr[10], ptr[9], ptr[8]);
-					add_extra_data(state.cur_dc, "TEST_CCR_FULL_1", config_buf);
+					add_extra_data(state.cur_dc, "TEST_CCR_FULL_1",
+						       format_string_std("START=%04u-%02u-%02u %02u:%02u:%02u,TEST=%02X%02X%02X%02X,RESULT=%02X%02X%02X%02X",
+									  tm.tm_year, tm.tm_mon + 1, tm.tm_mday, tm.tm_hour, tm.tm_min, tm.tm_sec, ptr[7], ptr[6], ptr[5], ptr[4], ptr[11], ptr[10], ptr[9], ptr[8]));
 					break;
 				case 1: // TEST_CCR_PARTIAL_1
 					utc_mkdate(parse_dlf_timestamp(ptr + 12), &tm);
-					snprintf(config_buf, sizeof(config_buf), "START=%04u-%02u-%02u %02u:%02u:%02u,TEST=%02X%02X%02X%02X,RESULT=%02X%02X%02X%02X", tm.tm_year, tm.tm_mon + 1, tm.tm_mday, tm.tm_hour, tm.tm_min, tm.tm_sec, ptr[7], ptr[6], ptr[5], ptr[4], ptr[11], ptr[10], ptr[9], ptr[8]);
-					add_extra_data(state.cur_dc, "TEST_CCR_PARTIAL_1", config_buf);
+					add_extra_data(state.cur_dc, "TEST_CCR_PARTIAL_1",
+						       format_string_std("START=%04u-%02u-%02u %02u:%02u:%02u,TEST=%02X%02X%02X%02X,RESULT=%02X%02X%02X%02X",
+									 tm.tm_year, tm.tm_mon + 1, tm.tm_mday, tm.tm_hour, tm.tm_min, tm.tm_sec, ptr[7], ptr[6], ptr[5], ptr[4], ptr[11], ptr[10], ptr[9], ptr[8]));
 					break;
 				case 2: // CFG_OXYGEN_CALIBRATION
 					utc_mkdate(parse_dlf_timestamp(ptr + 12), &tm);
@@ -2135,12 +2136,14 @@ int parse_dlf_buffer(unsigned char *buffer, size_t size, struct divelog *log)
 					o2_sensor_calibration_values[1] = (ptr[7] << 8) + ptr[6];
 					o2_sensor_calibration_values[2] = (ptr[9] << 8) + ptr[8];
 					o2_sensor_calibration_values[3] = (ptr[11] << 8) + ptr[10];
-					snprintf(config_buf, sizeof(config_buf), "%04u,%04u,%04u,%04u,TIME=%04u-%02u-%02u %02u:%02u:%02u", o2_sensor_calibration_values[0], o2_sensor_calibration_values[1], o2_sensor_calibration_values[2], o2_sensor_calibration_values[3], tm.tm_year, tm.tm_mon + 1, tm.tm_mday, tm.tm_hour, tm.tm_min, tm.tm_sec);
-					add_extra_data(state.cur_dc, "CFG_OXYGEN_CALIBRATION", config_buf);
+					add_extra_data(state.cur_dc, "CFG_OXYGEN_CALIBRATION",
+						       format_string_std("%04u,%04u,%04u,%04u,TIME=%04u-%02u-%02u %02u:%02u:%02u",
+									 o2_sensor_calibration_values[0], o2_sensor_calibration_values[1], o2_sensor_calibration_values[2], o2_sensor_calibration_values[3], tm.tm_year, tm.tm_mon + 1, tm.tm_mday, tm.tm_hour, tm.tm_min, tm.tm_sec));
 					break;
 				case 3: // CFG_SERIAL
-					snprintf(config_buf, sizeof(config_buf), "PRODUCT=%c%c%c%c,SERIAL=%c%c%c%c%c%c%c%c", ptr[4], ptr[5], ptr[6], ptr[7], ptr[8], ptr[9], ptr[10], ptr[11], ptr[12], ptr[13], ptr[14], ptr[15]);
-					add_extra_data(state.cur_dc, "CFG_SERIAL", config_buf);
+					add_extra_data(state.cur_dc, "CFG_SERIAL",
+						       format_string_std("PRODUCT=%c%c%c%c,SERIAL=%c%c%c%c%c%c%c%c",
+									 ptr[4], ptr[5], ptr[6], ptr[7], ptr[8], ptr[9], ptr[10], ptr[11], ptr[12], ptr[13], ptr[14], ptr[15]));
 					break;
 				case 4: // CFG_CONFIG_DECO
 					switch ((ptr[5] & 0xC0) >> 6) {
@@ -2158,12 +2161,15 @@ int parse_dlf_buffer(unsigned char *buffer, size_t size, struct divelog *log)
 							break;
 					}
 
-					snprintf(config_buf, sizeof(config_buf), "%s,%s,%s,safety stop required=%s,last_stop=%s,deco_algorithm=%s,stop_rounding=%u,deep_stops=%s", (ptr[4] & 0x80) ? "imperial" : "metric", (ptr[4] & 0x40) ? "sea" : "fresh", (ptr[4] & 0x30) ? "stops" : "ceiling", (ptr[4] & 0x10) ? "yes" : "no", (ptr[4] & 0x08) ? "6m" : "3m", (ptr[4] & 0x04) ? "VPM" : "Buhlmann+GF", (ptr[4] & 0x03) ? (ptr[4] & 0x03) * 30 : 1, deep_stops);
-					add_extra_data(state.cur_dc, "CFG_CONFIG_DECO part 1", config_buf);
-					snprintf(config_buf, sizeof(config_buf), "deep_stop_len=%u min,gas_switch_len=%u min,gf_low=%u,gf_high=%u,gf_low_bailout=%u,gf_high_bailout=%u,ppO2_low=%4.2f,ppO2_high=%4.2f", (ptr[5] & 0x38) >> 3, ptr[5] & 0x07, ptr[6], ptr[7], ptr[8], ptr[9], ptr[10] / 100.0f, ptr[11] / 100.0f);
-					add_extra_data(state.cur_dc, "CFG_CONFIG_DECO part 2", config_buf);
-					snprintf(config_buf, sizeof(config_buf), "alarm_global=%u,alarm_cns=%u,alarm_ppO2=%u,alarm_ceiling=%u,alarm_stop_miss=%u,alarm_decentrate=%u,alarm_ascentrate=%u", (ptr[12] & 0x80) >> 7, (ptr[12] & 0x40) >> 6, (ptr[12] & 0x20) >> 5, (ptr[12] & 0x10) >> 4, (ptr[12] & 0x08) >> 3, (ptr[12] & 0x04) >> 2, (ptr[12] & 0x02) >> 1);
-					add_extra_data(state.cur_dc, "CFG_CONFIG_DECO part 3", config_buf);
+					add_extra_data(state.cur_dc, "CFG_CONFIG_DECO part 1",
+						       format_string_std("%s,%s,%s,safety stop required=%s,last_stop=%s,deco_algorithm=%s,stop_rounding=%u,deep_stops=%s",
+									 (ptr[4] & 0x80) ? "imperial" : "metric", (ptr[4] & 0x40) ? "sea" : "fresh", (ptr[4] & 0x30) ? "stops" : "ceiling", (ptr[4] & 0x10) ? "yes" : "no", (ptr[4] & 0x08) ? "6m" : "3m", (ptr[4] & 0x04) ? "VPM" : "Buhlmann+GF", (ptr[4] & 0x03) ? (ptr[4] & 0x03) * 30 : 1, deep_stops));
+					add_extra_data(state.cur_dc, "CFG_CONFIG_DECO part 2",
+						       format_string_std("deep_stop_len=%u min,gas_switch_len=%u min,gf_low=%u,gf_high=%u,gf_low_bailout=%u,gf_high_bailout=%u,ppO2_low=%4.2f,ppO2_high=%4.2f",
+									 (ptr[5] & 0x38) >> 3, ptr[5] & 0x07, ptr[6], ptr[7], ptr[8], ptr[9], ptr[10] / 100.0f, ptr[11] / 100.0f));
+					add_extra_data(state.cur_dc, "CFG_CONFIG_DECO part 3",
+						       format_string_std("alarm_global=%u,alarm_cns=%u,alarm_ppO2=%u,alarm_ceiling=%u,alarm_stop_miss=%u,alarm_decentrate=%u,alarm_ascentrate=%u",
+									 (ptr[12] & 0x80) >> 7, (ptr[12] & 0x40) >> 6, (ptr[12] & 0x20) >> 5, (ptr[12] & 0x10) >> 4, (ptr[12] & 0x08) >> 3, (ptr[12] & 0x04) >> 2, (ptr[12] & 0x02) >> 1));
 					break;
 				case 5: // CFG_VERSION
 					switch (ptr[4]) {
@@ -2180,8 +2186,9 @@ int parse_dlf_buffer(unsigned char *buffer, size_t size, struct divelog *log)
 							device = "UNKNOWN";
 							break;
 					}
-					snprintf(config_buf, sizeof(config_buf), "DEVICE=%s,HW=%d.%d,FW=%d.%d.%d.%d,FLAGS=%04X", device, ptr[5], ptr[6], ptr[7], ptr[8], ptr[9], (ptr[15] << 24) + (ptr[14] << 16) + (ptr[13] << 8) + (ptr[12]), (ptr[11] << 8) + ptr[10]);
-					add_extra_data(state.cur_dc, "CFG_VERSION", config_buf);
+					add_extra_data(state.cur_dc, "CFG_VERSION",
+						       format_string_std("DEVICE=%s,HW=%d.%d,FW=%d.%d.%d.%d,FLAGS=%04X",
+									 device, ptr[5], ptr[6], ptr[7], ptr[8], ptr[9], (ptr[15] << 24) + (ptr[14] << 16) + (ptr[13] << 8) + (ptr[12]), (ptr[11] << 8) + ptr[10]));
 					break;
 			}
 			break;
diff --git a/core/save-git.cpp b/core/save-git.cpp
index d8d85ef0b..0e4de1867 100644
--- a/core/save-git.cpp
+++ b/core/save-git.cpp
@@ -119,12 +119,11 @@ static void save_tags(struct membuffer *b, struct tag_entry *tags)
 	put_string(b, "\n");
 }
 
-static void save_extra_data(struct membuffer *b, struct extra_data *ed)
+static void save_extra_data(struct membuffer *b, const struct divecomputer *dc)
 {
-	while (ed) {
-		if (ed->key && ed->value)
-			put_format(b, "keyvalue \"%s\" \"%s\"\n", ed->key ? : "", ed->value ? : "");
-		ed = ed->next;
+	for (const auto &ed: dc->extra_data) {
+		if (!ed.key.empty() && !ed.value.empty())
+			put_format(b, "keyvalue \"%s\" \"%s\"\n", ed.key.c_str(), ed.value.c_str());
 	}
 }
 
@@ -442,7 +441,7 @@ static void save_dc(struct membuffer *b, struct dive *dive, struct divecomputer
 	save_salinity(b, dc);
 	put_duration(b, dc->surfacetime, "surfacetime ", "min\n");
 
-	save_extra_data(b, dc->extra_data);
+	save_extra_data(b, dc);
 	save_events(b, dive, dc->events);
 	save_samples(b, dive, dc);
 }
diff --git a/core/save-xml.cpp b/core/save-xml.cpp
index 2530df97e..b4748649d 100644
--- a/core/save-xml.cpp
+++ b/core/save-xml.cpp
@@ -396,16 +396,15 @@ static void save_tags(struct membuffer *b, struct tag_entry *entry)
 	}
 }
 
-static void save_extra_data(struct membuffer *b, struct extra_data *ed)
+static void save_extra_data(struct membuffer *b, const struct divecomputer *dc)
 {
-	while (ed) {
-		if (ed->key && ed->value) {
+	for (const auto &ed: dc->extra_data) {
+		if (!ed.key.empty() && !ed.value.empty()) {
 			put_string(b, "  <extradata");
-			show_utf8(b, ed->key, " key='", "'", 1);
-			show_utf8(b, ed->value, " value='", "'", 1);
+			show_utf8(b, ed.key.c_str(), " key='", "'", 1);
+			show_utf8(b, ed.value.c_str(), " value='", "'", 1);
 			put_string(b, " />\n");
 		}
-		ed = ed->next;
 	}
 }
 
@@ -471,7 +470,7 @@ static void save_dc(struct membuffer *b, struct dive *dive, struct divecomputer
 	save_airpressure(b, dc);
 	save_salinity(b, dc);
 	put_duration(b, dc->surfacetime, "  <surfacetime>", " min</surfacetime>\n");
-	save_extra_data(b, dc->extra_data);
+	save_extra_data(b, dc);
 	save_events(b, dive, dc->events);
 	save_samples(b, dive, dc);
 
diff --git a/core/uemis.cpp b/core/uemis.cpp
index 22ce6359a..7ff20ea3e 100644
--- a/core/uemis.cpp
+++ b/core/uemis.cpp
@@ -18,6 +18,7 @@
 #include "divecomputer.h"
 #include "divesite.h"
 #include "errorhelper.h"
+#include "format.h"
 #include "sample.h"
 #include <libdivecomputer/parser.h>
 #include <libdivecomputer/version.h>
@@ -356,22 +357,20 @@ void uemis::parse_divelog_binary(std::string_view base64, struct dive *dive)
 		dive->dc.duration.seconds = sample->time.seconds - 1;
 
 	/* get data from the footer */
-	char buffer[24];
-
-	snprintf(buffer, sizeof(buffer), "%1u.%02u", data[18], data[17]);
-	add_extra_data(dc, "FW Version", buffer);
-	snprintf(buffer, sizeof(buffer), "%08x", *(uint32_t *)(data.data() + 9));
-	add_extra_data(dc, "Serial", buffer);
-	snprintf(buffer, sizeof(buffer), "%d", *(uint16_t *)(data.data() + i + 35));
-	add_extra_data(dc, "main battery after dive", buffer);
-	snprintf(buffer, sizeof(buffer), "%0u:%02u", FRACTION_TUPLE(*(uint16_t *)(data.data() + i + 24), 60));
-	add_extra_data(dc, "no fly time", buffer);
-	snprintf(buffer, sizeof(buffer), "%0u:%02u", FRACTION_TUPLE(*(uint16_t *)(data.data() + i + 26), 60));
-	add_extra_data(dc, "no dive time", buffer);
-	snprintf(buffer, sizeof(buffer), "%0u:%02u", FRACTION_TUPLE(*(uint16_t *)(data.data() + i + 28), 60));
-	add_extra_data(dc, "desat time", buffer);
-	snprintf(buffer, sizeof(buffer), "%u", *(uint16_t *)(data.data() + i + 30));
-	add_extra_data(dc, "allowed altitude", buffer);
+	add_extra_data(dc, "FW Version",
+		       format_string_std("%1u.%02u", data[18], data[17]));
+	add_extra_data(dc, "Serial",
+		       format_string_std("%08x", *(uint32_t *)(data.data() + 9)));
+	add_extra_data(dc, "main battery after dive",
+		       std::to_string(*(uint16_t *)(data.data() + i + 35)));
+	add_extra_data(dc, "no fly time",
+		       format_string_std("%0u:%02u", FRACTION_TUPLE(*(uint16_t *)(data.data() + i + 24), 60)));
+	add_extra_data(dc, "no dive time",
+		       format_string_std("%0u:%02u", FRACTION_TUPLE(*(uint16_t *)(data.data() + i + 26), 60)));
+	add_extra_data(dc, "desat time",
+		       format_string_std("%0u:%02u", FRACTION_TUPLE(*(uint16_t *)(data.data() + i + 28), 60)));
+	add_extra_data(dc, "allowed altitude",
+		       std::to_string(*(uint16_t *)(data.data() + i + 30)));
 
 	return;
 }
diff --git a/qt-models/divecomputerextradatamodel.cpp b/qt-models/divecomputerextradatamodel.cpp
index d0cf2d98d..a47e6af82 100644
--- a/qt-models/divecomputerextradatamodel.cpp
+++ b/qt-models/divecomputerextradatamodel.cpp
@@ -1,7 +1,6 @@
 // SPDX-License-Identifier: GPL-2.0
 #include "qt-models/divecomputerextradatamodel.h"
 #include "core/divecomputer.h"
-#include "core/extradata.h"
 #include "core/metrics.h"
 
 ExtraDataModel::ExtraDataModel(QObject *parent) : CleanerTableModel(parent)
@@ -21,7 +20,7 @@ QVariant ExtraDataModel::data(const QModelIndex &index, int role) const
 {
 	if (!index.isValid() || index.row() > (int)items.size())
 		return QVariant();
-	const Item &item = items[index.row()];
+	const extra_data &item = items[index.row()];
 
 	switch (role) {
 	case Qt::FontRole:
@@ -31,9 +30,9 @@ QVariant ExtraDataModel::data(const QModelIndex &index, int role) const
 	case Qt::DisplayRole:
 		switch (index.column()) {
 		case KEY:
-			return item.key;
+			return QString::fromStdString(item.key);
 		case VALUE:
-			return item.value;
+			return QString::fromStdString(item.value);
 		}
 		return QVariant();
 	}
@@ -48,11 +47,9 @@ int ExtraDataModel::rowCount(const QModelIndex&) const
 void ExtraDataModel::updateDiveComputer(const struct divecomputer *dc)
 {
 	beginResetModel();
-	struct extra_data *ed = dc ? dc->extra_data : nullptr;
-	items.clear();
-	while (ed) {
-		items.push_back({ ed->key, ed->value });
-		ed = ed->next;
-	}
+	if (dc)
+		items = dc->extra_data;
+	else
+		items.clear();
 	endResetModel();
 }
diff --git a/qt-models/divecomputerextradatamodel.h b/qt-models/divecomputerextradatamodel.h
index 9af4028eb..be1d8bb40 100644
--- a/qt-models/divecomputerextradatamodel.h
+++ b/qt-models/divecomputerextradatamodel.h
@@ -3,6 +3,7 @@
 #define DIVECOMPUTEREXTRADATAMODEL_H
 
 #include "cleanertablemodel.h"
+#include "core/extradata.h"
 
 struct divecomputer;
 
@@ -22,11 +23,7 @@ public:
 	void updateDiveComputer(const struct divecomputer *dc);
 
 private:
-	struct Item {
-		QString key;
-		QString value;
-	};
-	std::vector<Item> items;
+	std::vector<extra_data> items;
 };
 
 #endif