Correct implementation of gcc specific internal functions

Last bit not implemented by a4496b927b
Squash and rebase of https://github.com/arduino/Arduino/pull/108

cores/arduino/abi.cpp

@@ -15,21 +15,59 @@
   License along with this library; if not, write to the Free Software
   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */
+#include <abi.h>
+#include <stdint.h>
+#include <exception>
 
-#include <stdlib.h>
+#include <avr/io.h>
+#include <avr/interrupt.h>
 
-extern "C" void __cxa_pure_virtual(void) __attribute__ ((__noreturn__));
-extern "C" void __cxa_deleted_virtual(void) __attribute__ ((__noreturn__));
+namespace {
+// guard is an integer type big enough to hold flag and a mutex.
+// By default gcc uses long long int and avr ABI does not change it
+// So we have 32 or 64 bits available. Actually, we need 16.
+
+inline char& flag_part(__guard *g) {
+    return *(reinterpret_cast<char*>(g));
+}
+
+inline uint8_t& sreg_part(__guard *g) {
+    return *(reinterpret_cast<uint8_t*>(g) + sizeof(char));
+}
+}
+
+int __cxa_guard_acquire(__guard *g) {
+    uint8_t oldSREG = SREG;
+    cli();
+    // Initialization of static variable has to be done with blocked interrupts
+    // because if this function is called from interrupt and sees that somebody
+    // else is already doing initialization it MUST wait until initializations
+    // is complete. That's impossible.
+    // If you don't want this overhead compile with -fno-threadsafe-statics
+    if (flag_part(g)) {
+        SREG = oldSREG;
+        return false;
+    } else {
+        sreg_part(g) = oldSREG;
+        return true;
+    }
+}
+
+void __cxa_guard_release (__guard *g) {
+    flag_part(g) = 1;
+    SREG = sreg_part(g);
+}
+
+void __cxa_guard_abort (__guard *g) {
+    SREG = sreg_part(g);
+}
 
 void __cxa_pure_virtual(void) {
-  // We might want to write some diagnostics to uart in this case
-  //std::terminate();
-  abort();
+    // We might want to write some diagnostics to uart in this case
+    std::terminate();
 }
 
 void __cxa_deleted_virtual(void) {
-  // We might want to write some diagnostics to uart in this case
-  //std::terminate();
-  abort();
-}
-
+    // We might want to write some diagnostics to uart in this case
+    std::terminate();
+}