Merge pull request #1994 from BytesGalore/EasyCPPMixing_samr21_xpro_support_fix

cpu/samd21 C++ samr21-xpro support fix

boards/samr21-xpro/Makefile.features

@@ -1 +1 @@
-FEATURES_PROVIDED += periph_gpio
+FEATURES_PROVIDED += periph_gpio cpp

boards/samr21-xpro/Makefile.include

@@ -8,6 +8,7 @@ export PORT ?= /dev/ttyACM0
 # define tools used for building the project
 export PREFIX = arm-none-eabi-
 export CC = $(PREFIX)gcc
+export CXX = $(PREFIX)g++
 export AR = $(PREFIX)ar
 export AS = $(PREFIX)as
 export LINK = $(PREFIX)gcc
@@ -30,6 +31,10 @@ export OFLAGS += -O binary
 export FFLAGS += $(HEXFILE)
 export TERMFLAGS += "$(PORT)"
 
+# unwanted (CXXUWFLAGS) and extra (CXXEXFLAGS) flags for c++
+export CXXUWFLAGS +=
+export CXXEXFLAGS +=
+
 # use the nano-specs of the NewLib when available
 ifeq ($(shell $(LINK) -specs=nano.specs -E - 2>/dev/null >/dev/null </dev/null ; echo $$?),0)
 export LINKFLAGS += -specs=nano.specs -lc -lnosys

cpu/samd21/syscalls.c

@@ -150,6 +150,7 @@ pid_t _getpid(void)
  *
  * @return      TODO
  */
+__attribute__ ((weak))
 int _kill_r(struct _reent *r, pid_t pid, int sig)
 {
     r->_errno = ESRCH;                      /* not implemented yet */
@@ -317,3 +318,18 @@ int _unlink_r(struct _reent *r, char* path)
     r->_errno = ENODEV;                     /* not implemented yet */
     return -1;
 }
+
+/**
+ * @brief Send a signal to a thread
+ *
+ * @param[in] pid the pid to send to
+ * @param[in] sig the signal to send
+ *
+ * @return TODO
+ */
+__attribute__ ((weak))
+int _kill(int pid, int sig)
+{
+    errno = ESRCH;                         /* not implemented yet */
+    return -1;
+}