cpp: Use modules for cpp and libstdcpp

Also add better error message when kconfig or make includes a .cpp without cpp module.

Makefile.base

@@ -67,9 +67,14 @@ ifeq ($(strip $(ASSMSRC))$(NO_AUTO_SRC),)
   ASSMSRC := $(wildcard *.S)
 endif
 
+
 ifneq (,$(SRCXX))
-  ifeq (,$(filter cpp,$(FEATURES_USED)))
+  ifeq (,$(filter cpp,$(USEMODULE)))
-    $(error Found C++ source, but feature "cpp" is not used. Add "FEATURES_REQUIRED += cpp")
+    ifneq (1,$(TEST_KCONFIG))
+      $(error Found C++ source, but feature "cpp" is not used. Add "FEATURES_REQUIRED += cpp")
+    else
+      $(error Found C++ source, but "cpp" module is not used. Enable the MODULE_CPP in Kconfig)
+    endif
   endif
 endif
 

Makefile.dep

@@ -104,7 +104,13 @@ FEATURES_OPTIONAL += no_idle_thread
 
 ifneq (,$(filter libstdcpp,$(FEATURES_USED)))
   # Also use C++ if libstdc++ is used
-  FEATURES_REQUIRED += cpp
+  USEMODULE += cpp
+  USEMODULE += libstdcpp
+endif
+
+ifneq (,$(filter cpp,$(FEATURES_USED)))
+  # Also use C++ if libstdc++ is used
+  USEMODULE += cpp
 endif
 
 ifneq (,$(filter test_utils_interactive_sync,$(USEMODULE)))

Makefile.include

@@ -623,7 +623,7 @@ else
 endif
 
 # variables used to compile and link c++
-ifneq (,$(filter cpp,$(FEATURES_USED)))
+ifneq (,$(filter cpp,$(USEMODULE)))
   CPPMIX ?= 1
 endif
 

makefiles/pseudomodules.inc.mk

@@ -20,6 +20,7 @@ PSEUDOMODULES += cord_ep_standalone
 PSEUDOMODULES += core_%
 PSEUDOMODULES += cortexm_fpu
 PSEUDOMODULES += cortexm_svc
+PSEUDOMODULES += cpp
 PSEUDOMODULES += cpu_check_address
 PSEUDOMODULES += dbgpin
 PSEUDOMODULES += devfs_%
@@ -75,6 +76,7 @@ PSEUDOMODULES += ieee802154_submac
 PSEUDOMODULES += ina3221_alerts
 PSEUDOMODULES += l2filter_blacklist
 PSEUDOMODULES += l2filter_whitelist
+PSEUDOMODULES += libstdcpp
 PSEUDOMODULES += lis2dh12_i2c
 PSEUDOMODULES += lis2dh12_int
 PSEUDOMODULES += lis2dh12_spi

sys/Kconfig

@@ -58,6 +58,18 @@ rsource "usb/Kconfig"
 rsource "xtimer/Kconfig"
 rsource "ztimer/Kconfig"
 
+config MODULE_CPP
+    bool "Use CPP compiler"
+    depends on TEST_KCONFIG
+    depends on HAS_CPP
+
+config MODULE_LIBSTDCPP
+    bool "Use the CPP standard library"
+    depends on TEST_KCONFIG
+    depends on HAS_LIBSTDCPP
+    depends on HAS_CPP
+    select MODULE_CPP
+
 config MODULE_SYS
     bool
     default y

sys/arduino/Kconfig

@@ -16,8 +16,10 @@ menuconfig MODULE_ARDUINO
     imply MODULE_PERIPH_SPI
     depends on HAS_ARDUINO
     depends on HAS_PERIPH_GPIO
+    depends on HAS_CPP
     depends on TEST_KCONFIG
     select MODULE_PERIPH_GPIO
+    select MODULE_CPP
     select MODULE_ARDUINO_SKETCHES
     select MODULE_FMT
     select MODULE_ZTIMER