software/demo: Make hellocpp optional (only build with --with-cxx) to avoid adding g++ as a dependency for an optional feature.

litex/soc/software/demo/Makefile

@@ -3,7 +3,10 @@ BUILD_DIR?=../build/
 include $(BUILD_DIR)/software/include/generated/variables.mak
 include $(SOC_DIRECTORY)/software/common.mak
 
-OBJECTS=isr.o donut.o helloc.o hellocpp.o main.o
+OBJECTS   = isr.o donut.o helloc.o main.o
+ifdef WITH_CXX
+	OBJECTS += hellocpp.o
+endif
 
 all: demo.bin
 
@@ -33,6 +36,7 @@ donut.o: CFLAGS += -w
 helloc.o: CFLAGS += -w
 
 hellocpp.o: CXXFLAGS += -w
+
 %.o: %.cpp
 	$(compilexx)
 

litex/soc/software/demo/demo.py

@@ -12,7 +12,8 @@ from distutils.dir_util import copy_tree
 
 def main():
     parser = argparse.ArgumentParser(description="LiteX Bare Metal Demo App.")
-    parser.add_argument("--build-path", help="Target's build path (ex build/board_name)", required=True)
+    parser.add_argument("--build-path", help="Target's build path (ex build/board_name).", required=True)
+    parser.add_argument("--with-cxx",   action="store_true", help="Enable CXX support.")
     args = parser.parse_args()
 
     # Create demo directory
@@ -24,7 +25,7 @@ def main():
 
     # Compile demo
     build_path = args.build_path if os.path.isabs(args.build_path) else os.path.join("..", args.build_path)
-    os.system(f"export BUILD_DIR={build_path} && cd demo && make")
+    os.system(f"export BUILD_DIR={build_path} && {'export WITH_CXX=1 &&' if args.with_cxx else ''} cd demo && make")
 
     # Copy demo.bin
     os.system("cp demo/demo.bin ./")

litex/soc/software/demo/main.c

@@ -88,7 +88,9 @@ static void help(void)
 #endif
 	puts("donut              - Spinning Donut demo");
 	puts("helloc             - Hello C");
+#ifdef WITH_CXX
 	puts("hellocpp           - Hello C++");
+#endif
 }
 
 /*-----------------------------------------------------------------------*/
@@ -148,6 +150,7 @@ static void helloc_cmd(void)
 	helloc();
 }
 
+#ifdef WITH_CXX
 extern void hellocpp(void);
 
 static void hellocpp_cmd(void)
@@ -155,6 +158,8 @@ static void hellocpp_cmd(void)
 	printf("Hello C++ demo...\n");
 	hellocpp();
 }
+#endif
+
 /*-----------------------------------------------------------------------*/
 /* Console service / Main                                                */
 /*-----------------------------------------------------------------------*/
@@ -179,8 +184,10 @@ static void console_service(void)
 		donut_cmd();
 	else if(strcmp(token, "helloc") == 0)
 		helloc_cmd();
+#ifdef WITH_CXX
 	else if(strcmp(token, "hellocpp") == 0)
 		hellocpp_cmd();
+#endif
 	prompt();
 }