systemcmds: convert c -> c++

src/systemcmds/dumpfile/CMakeLists.txt

@@ -36,7 +36,7 @@ px4_add_module(
 	STACK_MAIN 4096
 	COMPILE_FLAGS
 	SRCS
-		dumpfile.c
+		dumpfile.cpp
 	DEPENDS
 	)
 

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;
 	}