systemcmds: convert c -> c++

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
 	)
 

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);