diff --git a/src/systemcmds/bl_update/CMakeLists.txt b/src/systemcmds/bl_update/CMakeLists.txt
index c3ea9ccf17..7e0ddc5075 100644
--- a/src/systemcmds/bl_update/CMakeLists.txt
+++ b/src/systemcmds/bl_update/CMakeLists.txt
@@ -37,5 +37,5 @@ px4_add_module(
 	COMPILE_FLAGS
 		-Wno-cast-align # TODO: fix and enable
 	SRCS
-		bl_update.c
+		bl_update.cpp
 )
diff --git a/src/systemcmds/bl_update/bl_update.c b/src/systemcmds/bl_update/bl_update.cpp
similarity index 97%
rename from src/systemcmds/bl_update/bl_update.c
rename to src/systemcmds/bl_update/bl_update.cpp
index d83e449f88..535402a468 100644
--- a/src/systemcmds/bl_update/bl_update.c
+++ b/src/systemcmds/bl_update/bl_update.cpp
@@ -66,8 +66,6 @@
 #  define STM_RAM_BASE        STM32_SRAM_BASE
 #endif
 
-__EXPORT int bl_update_main(int argc, char *argv[]);
-
 #if defined (CONFIG_STM32_STM32F4XXX) || defined (CONFIG_ARCH_CHIP_STM32F7) || \
     defined (CONFIG_ARCH_CHIP_STM32H7)
 
@@ -90,8 +88,7 @@ static void print_usage(const char *reason)
 #endif // defined (CONFIG_STM32_STM32F4XXX) || defined (CONFIG_ARCH_CHIP_STM32F7)
 
 
-int
-bl_update_main(int argc, char *argv[])
+extern "C" __EXPORT int bl_update_main(int argc, char *argv[])
 {
 #if !(defined (CONFIG_STM32_STM32F4XXX) || defined (CONFIG_ARCH_CHIP_STM32F7) \
     || defined (CONFIG_ARCH_CHIP_STM32H7))
@@ -144,9 +141,9 @@ bl_update_main(int argc, char *argv[])
 	image_size = (file_size + page_size) & ~page_size;
 #endif
 
-	uint8_t *buf = malloc(image_size);
+	uint8_t *buf = (uint8_t *)malloc(image_size);
 
-	if (buf == NULL)
+	if (buf == nullptr)
 	{
 		PX4_ERR("failed to allocate %jd bytes for firmware buffer", (intmax_t) file_size);
 		close(fd);
diff --git a/src/systemcmds/dumpfile/CMakeLists.txt b/src/systemcmds/dumpfile/CMakeLists.txt
index 28b589b2d2..e8a7c1c5ac 100644
--- a/src/systemcmds/dumpfile/CMakeLists.txt
+++ b/src/systemcmds/dumpfile/CMakeLists.txt
@@ -36,7 +36,7 @@ px4_add_module(
 	STACK_MAIN 4096
 	COMPILE_FLAGS
 	SRCS
-		dumpfile.c
+		dumpfile.cpp
 	DEPENDS
 	)
 
diff --git a/src/systemcmds/dumpfile/dumpfile.c b/src/systemcmds/dumpfile/dumpfile.cpp
similarity index 95%
rename from src/systemcmds/dumpfile/dumpfile.c
rename to src/systemcmds/dumpfile/dumpfile.cpp
index ce947518ea..21e7917c65 100644
--- a/src/systemcmds/dumpfile/dumpfile.c
+++ b/src/systemcmds/dumpfile/dumpfile.cpp
@@ -49,19 +49,15 @@
 
 #include <systemlib/err.h>
 
-__EXPORT int dumpfile_main(int argc, char *argv[]);
-
-static void print_usage(void)
+static void print_usage()
 {
 	PRINT_MODULE_DESCRIPTION("Dump file utility. Prints file size and contents in binary mode (don't replace LF with CR LF) to stdout.");
 
 	PRINT_MODULE_USAGE_NAME_SIMPLE("dumpfile", "command");
 	PRINT_MODULE_USAGE_ARG("<file>", "File to dump", false);
-
 }
 
-int
-dumpfile_main(int argc, char *argv[])
+extern "C" __EXPORT int dumpfile_main(int argc, char *argv[])
 {
 	if (argc < 2) {
 		print_usage();
@@ -72,7 +68,7 @@ dumpfile_main(int argc, char *argv[])
 	FILE *f;
 	f = fopen(argv[1], "r");
 
-	if (f == NULL) {
+	if (f == nullptr) {
 		PX4_ERR("Failed to open file (%i)", errno);
 		return 1;
 	}
diff --git a/src/systemcmds/esc_calib/CMakeLists.txt b/src/systemcmds/esc_calib/CMakeLists.txt
index 80c1764049..b41e849bd1 100644
--- a/src/systemcmds/esc_calib/CMakeLists.txt
+++ b/src/systemcmds/esc_calib/CMakeLists.txt
@@ -36,7 +36,7 @@ px4_add_module(
 	STACK_MAIN 4096
 	COMPILE_FLAGS
 	SRCS
-		esc_calib.c
+		esc_calib.cpp
 	DEPENDS
 	)
 
diff --git a/src/systemcmds/esc_calib/esc_calib.c b/src/systemcmds/esc_calib/esc_calib.cpp
similarity index 94%
rename from src/systemcmds/esc_calib/esc_calib.c
rename to src/systemcmds/esc_calib/esc_calib.cpp
index 6d60f9d311..d90bb62d1d 100644
--- a/src/systemcmds/esc_calib/esc_calib.c
+++ b/src/systemcmds/esc_calib/esc_calib.cpp
@@ -53,19 +53,13 @@
 #include <sys/ioctl.h>
 #include <sys/stat.h>
 
-
-
 #include "drivers/drv_pwm_output.h"
 
 #include <uORB/topics/actuator_controls.h>
 
-static void	usage(const char *reason);
-__EXPORT int	esc_calib_main(int argc, char *argv[]);
-
-static void
-usage(const char *reason)
+static void usage(const char *reason)
 {
-	if (reason != NULL) {
+	if (reason != nullptr) {
 		PX4_ERR("%s", reason);
 	}
 
@@ -82,14 +76,13 @@ usage(const char *reason)
 	PRINT_MODULE_USAGE_PARAM_STRING('d', "/dev/pwm_output0", "<file:dev>", "Select PWM output device", true);
 	PRINT_MODULE_USAGE_PARAM_INT('l', 1000, 0, 3000, "Low PWM value in us", true);
 	PRINT_MODULE_USAGE_PARAM_INT('h', 2000, 0, 3000, "High PWM value in us", true);
-	PRINT_MODULE_USAGE_PARAM_STRING('c', NULL, NULL, "select channels in the form: 1234 (1 digit per channel, 1=first)",
-					true);
+	PRINT_MODULE_USAGE_PARAM_STRING('c', nullptr, nullptr,
+					"select channels in the form: 1234 (1 digit per channel, 1=first)", true);
 	PRINT_MODULE_USAGE_PARAM_INT('m', -1, 0, 4096, "Select channels via bitmask (eg. 0xF, 3)", true);
 	PRINT_MODULE_USAGE_PARAM_FLAG('a', "Select all channels", true);
 }
 
-int
-esc_calib_main(int argc, char *argv[])
+extern "C" __EXPORT int esc_calib_main(int argc, char *argv[])
 {
 	const char *dev = PWM_OUTPUT0_DEVICE_PATH;
 	char *ep;
@@ -116,7 +109,7 @@ esc_calib_main(int argc, char *argv[])
 	}
 
 	int myoptind = 1;
-	const char *myoptarg = NULL;
+	const char *myoptarg = nullptr;
 
 	while ((ch = px4_getopt(argc, argv, "d:c:m:al:h:", &myoptind, &myoptarg)) != EOF) {
 		switch (ch) {
@@ -184,7 +177,7 @@ esc_calib_main(int argc, char *argv[])
 			break;
 
 		default:
-			usage(NULL);
+			usage(nullptr);
 			return 1;
 		}
 	}
@@ -201,10 +194,10 @@ esc_calib_main(int argc, char *argv[])
 
 	/* make sure no other source is publishing control values now */
 	struct actuator_controls_s actuators;
-	int act_sub = orb_subscribe(ORB_ID_VEHICLE_ATTITUDE_CONTROLS);
+	int act_sub = orb_subscribe(ORB_ID(actuator_controls_0));
 
 	/* clear changed flag */
-	orb_copy(ORB_ID_VEHICLE_ATTITUDE_CONTROLS, act_sub, &actuators);
+	orb_copy(ORB_ID(actuator_controls_0), act_sub, &actuators);
 
 	/* wait 50 ms */
 	px4_usleep(50000);
diff --git a/src/systemcmds/mft/mft.cpp b/src/systemcmds/mft/mft.cpp
index f113e8fa5e..f390441159 100644
--- a/src/systemcmds/mft/mft.cpp
+++ b/src/systemcmds/mft/mft.cpp
@@ -71,14 +71,12 @@
 
 #include <board_config.h>
 
-extern "C" __EXPORT int mft_main(int argc, char *argv[]);
-
 static int mft_status(void)
 {
 	return 0;
 }
 
-static void print_usage(void)
+static void print_usage()
 {
 	PRINT_MODULE_DESCRIPTION("Utility interact with the manifest");
 
@@ -86,9 +84,7 @@ static void print_usage(void)
 	PRINT_MODULE_USAGE_COMMAND_DESCR("query", "Returns true if not existed");
 }
 
-
-
-int mft_main(int argc, char *argv[])
+extern "C" __EXPORT int mft_main(int argc, char *argv[])
 {
 	static const char *keys[] = PX4_MFT_STR_TYPES;
 	static const px4_manifest_types_e types[] = PX4_MFT_TYPES;
diff --git a/src/systemcmds/microbench/microbench_main.cpp b/src/systemcmds/microbench/microbench_main.cpp
index e476a3b7c4..f56dbd6a2c 100644
--- a/src/systemcmds/microbench/microbench_main.cpp
+++ b/src/systemcmds/microbench/microbench_main.cpp
@@ -69,7 +69,7 @@ const struct {
 	{"microbench_matrix",	test_microbench_matrix,	0},
 	{"microbench_uorb",	test_microbench_uorb,	0},
 
-	{NULL,			NULL, 		0}
+	{nullptr,			nullptr, 		0}
 };
 
 #define NMICROBENCHMARKS (sizeof(microbenchmarks) / sizeof(microbenchmarks[0]))
@@ -93,7 +93,7 @@ static int microbench_all(int argc, char *argv[])
 static int microbench_runner(unsigned option)
 {
 	size_t i;
-	char *args[2] = {"all", NULL};
+	char *args[2] = {"all", nullptr};
 	unsigned int failcount = 0;
 	unsigned int testcount = 0;
 	unsigned int passed[NMICROBENCHMARKS];
diff --git a/src/systemcmds/motor_ramp/motor_ramp.cpp b/src/systemcmds/motor_ramp/motor_ramp.cpp
index 49f3665561..077d1fcff8 100644
--- a/src/systemcmds/motor_ramp/motor_ramp.cpp
+++ b/src/systemcmds/motor_ramp/motor_ramp.cpp
@@ -313,10 +313,10 @@ int prepare(int fd, unsigned long *max_channels)
 {
 	/* make sure no other source is publishing control values now */
 	struct actuator_controls_s actuators;
-	int act_sub = orb_subscribe(ORB_ID_VEHICLE_ATTITUDE_CONTROLS);
+	int act_sub = orb_subscribe(ORB_ID(actuator_controls_0));
 
 	/* clear changed flag */
-	orb_copy(ORB_ID_VEHICLE_ATTITUDE_CONTROLS, act_sub, &actuators);
+	orb_copy(ORB_ID(actuator_controls_0), act_sub, &actuators);
 
 	/* wait 50 ms */
 	px4_usleep(50000);
diff --git a/src/systemcmds/mtd/mtd.cpp b/src/systemcmds/mtd/mtd.cpp
index b3728fa69e..609c7ada29 100644
--- a/src/systemcmds/mtd/mtd.cpp
+++ b/src/systemcmds/mtd/mtd.cpp
@@ -135,7 +135,7 @@ static int mtd_status(void)
 	return ret;
 }
 
-static void	print_usage(void)
+static void print_usage()
 {
 #if !defined(CONSTRAINED_FLASH)
 
@@ -304,7 +304,7 @@ int mtd_rwtest(const mtd_instance_s &instance)
 int mtd_main(int argc, char *argv[])
 {
 	int myoptind = 1;
-	const char *myoptarg = NULL;
+	const char *myoptarg = nullptr;
 	int ch;
 	int instance = 0;
 
diff --git a/src/systemcmds/nshterm/CMakeLists.txt b/src/systemcmds/nshterm/CMakeLists.txt
index a8bb6ce56f..14f669c3de 100644
--- a/src/systemcmds/nshterm/CMakeLists.txt
+++ b/src/systemcmds/nshterm/CMakeLists.txt
@@ -36,7 +36,7 @@ px4_add_module(
 	PRIORITY "SCHED_PRIORITY_DEFAULT-30"
 	COMPILE_FLAGS
 	SRCS
-		nshterm.c
+		nshterm.cpp
 	DEPENDS
 	)
 
diff --git a/src/systemcmds/nshterm/nshterm.c b/src/systemcmds/nshterm/nshterm.cpp
similarity index 95%
rename from src/systemcmds/nshterm/nshterm.c
rename to src/systemcmds/nshterm/nshterm.cpp
index 7c44ac6882..aa4a615c2f 100644
--- a/src/systemcmds/nshterm/nshterm.c
+++ b/src/systemcmds/nshterm/nshterm.cpp
@@ -50,9 +50,7 @@
 #include <systemlib/err.h>
 #include <drivers/drv_hrt.h>
 
-__EXPORT int nshterm_main(int argc, char *argv[]);
-
-static void print_usage(void)
+static void print_usage()
 {
 	PRINT_MODULE_DESCRIPTION("Start an NSH shell on a given port.\n"
 				 "\n"
@@ -64,7 +62,7 @@ static void print_usage(void)
 	PRINT_MODULE_USAGE_ARG("<file:dev>", "Device on which to start the shell (eg. /dev/ttyACM0)", false);
 }
 
-int nshterm_main(int argc, char *argv[])
+extern "C" __EXPORT int nshterm_main(int argc, char *argv[])
 {
 	if (argc < 2) {
 		print_usage();
@@ -102,7 +100,7 @@ int nshterm_main(int argc, char *argv[])
 	dup2(fd, 1);
 	dup2(fd, 2);
 
-	nsh_consolemain(0, NULL);
+	nsh_consolemain(0, nullptr);
 
 	close(fd);
 
diff --git a/src/systemcmds/perf/CMakeLists.txt b/src/systemcmds/perf/CMakeLists.txt
index efae6abb16..a782e2c6ba 100644
--- a/src/systemcmds/perf/CMakeLists.txt
+++ b/src/systemcmds/perf/CMakeLists.txt
@@ -35,7 +35,7 @@ px4_add_module(
 	MAIN perf
 	COMPILE_FLAGS
 	SRCS
-		perf.c
+		perf.cpp
 	DEPENDS
 		perf
 	)
diff --git a/src/systemcmds/perf/perf.c b/src/systemcmds/perf/perf.cpp
similarity index 94%
rename from src/systemcmds/perf/perf.c
rename to src/systemcmds/perf/perf.cpp
index c58daf0359..1b8a2df65f 100644
--- a/src/systemcmds/perf/perf.c
+++ b/src/systemcmds/perf/perf.cpp
@@ -39,12 +39,9 @@
 #include <stdio.h>
 #include <string.h>
 
-#include <perf/perf_counter.h>
+#include <lib/perf/perf_counter.h>
 
-__EXPORT int perf_main(int argc, char *argv[]);
-
-
-static void print_usage(void)
+static void print_usage()
 {
 	PRINT_MODULE_DESCRIPTION("Tool to print performance counters");
 
@@ -55,8 +52,7 @@ static void print_usage(void)
 	PRINT_MODULE_USAGE_PARAM_COMMENT("Prints all performance counters if no arguments given");
 }
 
-
-int perf_main(int argc, char *argv[])
+extern "C" __EXPORT int perf_main(int argc, char *argv[])
 {
 	if (argc > 1) {
 		if (strcmp(argv[1], "reset") == 0) {
@@ -77,5 +73,3 @@ int perf_main(int argc, char *argv[])
 	fflush(stdout);
 	return 0;
 }
-
-
diff --git a/src/systemcmds/sd_bench/CMakeLists.txt b/src/systemcmds/sd_bench/CMakeLists.txt
index 8522c57ad0..9ab943a90b 100644
--- a/src/systemcmds/sd_bench/CMakeLists.txt
+++ b/src/systemcmds/sd_bench/CMakeLists.txt
@@ -35,7 +35,7 @@ px4_add_module(
 	MAIN sd_bench
 	COMPILE_FLAGS
 	SRCS
-		sd_bench.c
+		sd_bench.cpp
 	DEPENDS
 	)
 
diff --git a/src/systemcmds/sd_bench/sd_bench.c b/src/systemcmds/sd_bench/sd_bench.cpp
similarity index 96%
rename from src/systemcmds/sd_bench/sd_bench.c
rename to src/systemcmds/sd_bench/sd_bench.cpp
index b15c6b5371..1f38364f19 100644
--- a/src/systemcmds/sd_bench/sd_bench.c
+++ b/src/systemcmds/sd_bench/sd_bench.cpp
@@ -58,8 +58,6 @@ typedef struct sdb_config {
 	unsigned int total_blocks_written;
 } sdb_config_t;
 
-static void	usage(void);
-
 /** sequential write speed test */
 static void write_test(int fd, sdb_config_t *cfg, uint8_t *block, int block_size);
 /** sequential read speed test */
@@ -72,12 +70,9 @@ static int read_test(int fd, sdb_config_t *cfg, uint8_t *block, int block_size);
  */
 static inline unsigned int time_fsync(int fd);
 
-__EXPORT int	sd_bench_main(int argc, char *argv[]);
-
 static const char *BENCHMARK_FILE = PX4_STORAGEDIR"/benchmark.tmp";
 
-static void
-usage()
+static void usage()
 {
 	PRINT_MODULE_DESCRIPTION("Test the speed of an SD Card");
 
@@ -91,34 +86,33 @@ usage()
 	PRINT_MODULE_USAGE_PARAM_FLAG('v', "Verify data and block number", true);
 }
 
-int
-sd_bench_main(int argc, char *argv[])
+extern "C" __EXPORT int sd_bench_main(int argc, char *argv[])
 {
 	int block_size = 4096;
 	bool verify = false;
 	bool keep = false;
 	int myoptind = 1;
 	int ch;
-	const char *myoptarg = NULL;
+	const char *myoptarg = nullptr;
 	sdb_config_t cfg;
 	cfg.synchronized = false;
 	cfg.num_runs = 5;
 	cfg.run_duration = 2000;
 	cfg.aligned = true;
-	uint8_t *block =  NULL;
+	uint8_t *block = nullptr;
 
 	while ((ch = px4_getopt(argc, argv, "b:r:d:ksuv", &myoptind, &myoptarg)) != EOF) {
 		switch (ch) {
 		case 'b':
-			block_size = strtol(myoptarg, NULL, 0);
+			block_size = strtol(myoptarg, nullptr, 0);
 			break;
 
 		case 'r':
-			cfg.num_runs = strtol(myoptarg, NULL, 0);
+			cfg.num_runs = strtol(myoptarg, nullptr, 0);
 			break;
 
 		case 'd':
-			cfg.run_duration = strtol(myoptarg, NULL, 0);
+			cfg.run_duration = strtol(myoptarg, nullptr, 0);
 			break;
 
 		case 'k':
@@ -259,7 +253,7 @@ void write_test(int fd, sdb_config_t *cfg, uint8_t *block, int block_size)
 
 int read_test(int fd, sdb_config_t *cfg, uint8_t *block, int block_size)
 {
-	uint8_t *read_block =  NULL;
+	uint8_t *read_block = nullptr;
 
 	PX4_INFO("");
 	PX4_INFO("Testing Sequential Read Speed of %d blocks", cfg->total_blocks_written);
diff --git a/src/systemcmds/sd_stress/CMakeLists.txt b/src/systemcmds/sd_stress/CMakeLists.txt
index 346218764c..e928abc707 100644
--- a/src/systemcmds/sd_stress/CMakeLists.txt
+++ b/src/systemcmds/sd_stress/CMakeLists.txt
@@ -35,6 +35,6 @@ px4_add_module(
 	MAIN sd_stress
 	COMPILE_FLAGS
 	SRCS
-		sd_stress.c
+		sd_stress.cpp
 	DEPENDS
 	)
diff --git a/src/systemcmds/sd_stress/sd_stress.c b/src/systemcmds/sd_stress/sd_stress.cpp
similarity index 96%
rename from src/systemcmds/sd_stress/sd_stress.c
rename to src/systemcmds/sd_stress/sd_stress.cpp
index 7095426074..05c9ba7044 100644
--- a/src/systemcmds/sd_stress/sd_stress.c
+++ b/src/systemcmds/sd_stress/sd_stress.cpp
@@ -49,16 +49,13 @@
 
 #include <drivers/drv_hrt.h>
 
-
 static const unsigned MAX_PATH_LEN = 52;
 
 static const char *TEMPDIR = PX4_STORAGEDIR"/stress";
 static const char *TEMPDIR2 = PX4_STORAGEDIR"/moved";
 static const char *TEMPFILE = "tmp";
 
-
-static void
-usage(void)
+static void usage()
 {
 	PRINT_MODULE_DESCRIPTION("Test operations on an SD Card");
 
@@ -175,23 +172,22 @@ static bool rename_dir(const char *old_dir, const char *new_dir)
 	return true;
 }
 
-int
-sd_stress_main(int argc, char *argv[])
+extern "C" __EXPORT int sd_stress_main(int argc, char *argv[])
 {
 	int myoptind = 1;
 	int ch;
-	const char *myoptarg = NULL;
+	const char *myoptarg = nullptr;
 	unsigned num_runs = 5;
 	unsigned num_bytes = 100;
 
 	while ((ch = px4_getopt(argc, argv, "r:b:", &myoptind, &myoptarg)) != EOF) {
 		switch (ch) {
 		case 'r':
-			num_runs = strtol(myoptarg, NULL, 0);
+			num_runs = strtol(myoptarg, nullptr, 0);
 			break;
 
 		case 'b':
-			num_bytes = strtol(myoptarg, NULL, 0);
+			num_bytes = strtol(myoptarg, nullptr, 0);
 			break;
 
 		default:
diff --git a/src/systemcmds/tests/CMakeLists.txt b/src/systemcmds/tests/CMakeLists.txt
index ddffe6ac5b..0f953e6767 100644
--- a/src/systemcmds/tests/CMakeLists.txt
+++ b/src/systemcmds/tests/CMakeLists.txt
@@ -55,8 +55,8 @@ set(srcs
 	test_parameters.cpp
 	test_perf.c
 	test_ppm.cpp
-	test_ppm_loopback.c
-	test_rc.c
+	test_ppm_loopback.cpp
+	test_rc.cpp
 	test_search_min.cpp
 	test_sleep.c
 	test_uart_baudchange.c
diff --git a/src/systemcmds/tests/test_mount.cpp b/src/systemcmds/tests/test_mount.cpp
index 2e7ddbf153..d7675714de 100644
--- a/src/systemcmds/tests/test_mount.cpp
+++ b/src/systemcmds/tests/test_mount.cpp
@@ -80,7 +80,7 @@ int test_mount(int argc, char *argv[])
 
 	if (d) {
 
-		while ((dir = readdir(d)) != NULL) {
+		while ((dir = readdir(d)) != nullptr) {
 			//printf("%s\n", dir->d_name);
 		}
 
diff --git a/src/systemcmds/tests/test_ppm_loopback.c b/src/systemcmds/tests/test_ppm_loopback.cpp
similarity index 98%
rename from src/systemcmds/tests/test_ppm_loopback.c
rename to src/systemcmds/tests/test_ppm_loopback.cpp
index af9879b71a..b257fb580a 100644
--- a/src/systemcmds/tests/test_ppm_loopback.c
+++ b/src/systemcmds/tests/test_ppm_loopback.cpp
@@ -32,7 +32,7 @@
  ****************************************************************************/
 
 /**
- * @file test_ppm_loopback.c
+ * @file test_ppm_loopback.cpp
  * Tests the PWM outputs and PPM input
  */
 
@@ -120,7 +120,7 @@ int test_ppm_loopback(int argc, char *argv[])
 
 	warnx("servo count: %d", servo_count);
 
-	struct pwm_output_values pwm_out = {.values = {0}, .channel_count = 0};
+	pwm_output_values pwm_out{};
 
 	for (unsigned i = 0; (i < servo_count) && (i < sizeof(pwm_values) / sizeof(pwm_values[0])); i++) {
 		pwm_out.values[i] = pwm_values[i];
diff --git a/src/systemcmds/tests/test_rc.c b/src/systemcmds/tests/test_rc.cpp
similarity index 99%
rename from src/systemcmds/tests/test_rc.c
rename to src/systemcmds/tests/test_rc.cpp
index 83fe6aa703..97f7065115 100644
--- a/src/systemcmds/tests/test_rc.c
+++ b/src/systemcmds/tests/test_rc.cpp
@@ -32,7 +32,7 @@
  ****************************************************************************/
 
 /**
- * @file test_rc.c
+ * @file test_rc.cpp
  * Tests RC input.
  */
 
diff --git a/src/systemcmds/top/top.cpp b/src/systemcmds/top/top.cpp
index 0dd921d05a..64658b540e 100644
--- a/src/systemcmds/top/top.cpp
+++ b/src/systemcmds/top/top.cpp
@@ -52,7 +52,7 @@
 #include <drivers/drv_hrt.h>
 #include <px4_platform_common/module.h>
 
-static void print_usage(void)
+static void print_usage()
 {
 	PRINT_MODULE_DESCRIPTION("Monitor running processes and their CPU, stack usage, priority and state");
 
diff --git a/src/systemcmds/usb_connected/CMakeLists.txt b/src/systemcmds/usb_connected/CMakeLists.txt
index fc56f45ab8..f06ba157a9 100644
--- a/src/systemcmds/usb_connected/CMakeLists.txt
+++ b/src/systemcmds/usb_connected/CMakeLists.txt
@@ -35,7 +35,7 @@ px4_add_module(
 	MAIN usb_connected
 	COMPILE_FLAGS
 	SRCS
-		usb_connected.c
+		usb_connected.cpp
 	DEPENDS
 	)
 
diff --git a/src/systemcmds/usb_connected/usb_connected.c b/src/systemcmds/usb_connected/usb_connected.cpp
similarity index 93%
rename from src/systemcmds/usb_connected/usb_connected.c
rename to src/systemcmds/usb_connected/usb_connected.cpp
index 76411d743a..8ce3b312de 100644
--- a/src/systemcmds/usb_connected/usb_connected.c
+++ b/src/systemcmds/usb_connected/usb_connected.cpp
@@ -32,7 +32,7 @@
  ****************************************************************************/
 
 /**
- * @file usb_connected.c
+ * @file usb_connected.cpp
  *
  * @author Andrew Tridgell
  */
@@ -45,11 +45,8 @@
 
 #include <board_config.h>
 
-__EXPORT int usb_connected_main(int argc, char *argv[]);
-
-static void print_usage(void)
+static void print_usage()
 {
-
 	PRINT_MODULE_DESCRIPTION("Utility to check if USB is connected. Was previously used in startup scripts.\n"
 				 "A return value of 0 means USB is connected, 1 otherwise."
 				);
@@ -57,8 +54,7 @@ static void print_usage(void)
 	PRINT_MODULE_USAGE_NAME_SIMPLE("usb_connected", "command");
 }
 
-int
-usb_connected_main(int argc, char *argv[])
+extern "C" __EXPORT int usb_connected_main(int argc, char *argv[])
 {
 	if (argc > 1) {
 		print_usage();
diff --git a/src/systemcmds/ver/CMakeLists.txt b/src/systemcmds/ver/CMakeLists.txt
index e4f3353fa0..708cde7604 100644
--- a/src/systemcmds/ver/CMakeLists.txt
+++ b/src/systemcmds/ver/CMakeLists.txt
@@ -35,7 +35,7 @@ px4_add_module(
 	MAIN ver
 	COMPILE_FLAGS
 	SRCS
-		ver.c
+		ver.cpp
 	DEPENDS
 		version
 	)
diff --git a/src/systemcmds/ver/ver.c b/src/systemcmds/ver/ver.cpp
similarity index 96%
rename from src/systemcmds/ver/ver.c
rename to src/systemcmds/ver/ver.cpp
index b5e9885f07..5028adff93 100644
--- a/src/systemcmds/ver/ver.c
+++ b/src/systemcmds/ver/ver.cpp
@@ -61,7 +61,7 @@ static const char px4_guid_str[]         = "px4guid";
 
 static void usage(const char *reason)
 {
-	if (reason != NULL) {
+	if (reason != nullptr) {
 		printf("%s\n\n", reason);
 	}
 
@@ -86,19 +86,17 @@ static void usage(const char *reason)
 			       "Hardware type to compare against (eg. V2). An OR comparison is used if multiple are specified", false);
 }
 
-__EXPORT int ver_main(int argc, char *argv[]);
-
-int ver_main(int argc, char *argv[])
+extern "C" __EXPORT int ver_main(int argc, char *argv[])
 {
 	/* defaults to an error */
 	int ret = 1;
 
 	/* first check if there are at least 2 params */
 	if (argc >= 2) {
-		if (argv[1] != NULL) {
+		if (argv[1] != nullptr) {
 
 			if (!strncmp(argv[1], sz_ver_hwcmp_str, sizeof(sz_ver_hwcmp_str))) {
-				if (argc >= 3 && argv[2] != NULL) {
+				if (argc >= 3 && argv[2] != nullptr) {
 					const char *board_name = px4_board_name();
 
 					for (int i = 2; i < argc; ++i) {
@@ -115,7 +113,7 @@ int ver_main(int argc, char *argv[])
 			}
 
 			if (!strncmp(argv[1], sz_ver_hwtypecmp_str, sizeof(sz_ver_hwtypecmp_str))) {
-				if (argc >= 3 && argv[2] != NULL) {
+				if (argc >= 3 && argv[2] != nullptr) {
 					const char *board_type = px4_board_sub_type();
 
 					for (int i = 2; i < argc; ++i) {
@@ -238,8 +236,8 @@ int ver_main(int argc, char *argv[])
 			if (show_all || !strncmp(argv[1], mcu_ver_str, sizeof(mcu_ver_str))) {
 
 				char rev = ' ';
-				const char *revstr = NULL;
-				const char *errata = NULL;
+				const char *revstr = nullptr;
+				const char *errata = nullptr;
 
 				int chip_version = board_mcu_version(&rev, &revstr, &errata);
 
@@ -249,7 +247,7 @@ int ver_main(int argc, char *argv[])
 				} else {
 					printf("MCU: %s, rev. %c\n", revstr, rev);
 
-					if (errata != NULL) {
+					if (errata != nullptr) {
 						printf("\nWARNING   WARNING   WARNING!\n"
 						       "Revision %c has a silicon errata:\n"
 						       "%s"