graphite2: update gralloc in Main.h

- With newer compiler / libraries, there is error G47DF2280: argument
1 value ‘18446744073709551560’ exceeds maximum object size
9223372036854775807 [-Werror=alloc-size-larger-than=]
- Copied in the newer implementation from graphite.git.

Change-Id: I904fff90c7cce9331aeb19c4854b47541c498df0

Lib/src/graphite2/src/inc/Main.h

@@ -77,15 +77,61 @@ class telemetry::category
 struct telemetry  {};
 #endif
 
+// Checked multiplaction to catch overflow or underflow when allocating memory
+#if defined(__has_builtin)
+  #if __has_builtin(__builtin_mul_overflow)
+    #define HAVE_BUILTIN_OVERFLOW
+  #endif
+#elif defined(__GNUC__) && (__GNUC__ >= 5) && !defined(__INTEL_COMPILER)
+  #define HAVE_BUILTIN_OVERFLOW
+#endif
+#if defined(__has_include)
+  #if __has_include(<intsafe.h>) && !defined(__CYGWIN__)
+    #define HAVE_INTSAFE_H
+  #endif
+#elif defined(_WIN32)
+  #define HAVE_INTSAFE_H
+#endif
+
+// Need to import intsafe into the top level namespace
+#if defined(HAVE_INTSAFE_H)
+} // namespace graphite2
+
+#include <intsafe.h>
+
+namespace graphite2 {
+#endif
+
+#if defined(HAVE_BUILTIN_OVERFLOW)
+inline
+bool checked_mul(const size_t a, const size_t b, size_t & t) {
+    return __builtin_mul_overflow(a, b, &t);
+}
+#elif defined(HAVE_INTSAFE_H)
+inline
+bool checked_mul(const size_t a, const size_t b, size_t & t) {
+    return SizeTMult(a, b, &t) == INTSAFE_E_ARITHMETIC_OVERFLOW;
+}
+#else
+inline
+bool checked_mul(const size_t a, const size_t b, size_t & t) {
+  t = a*b;
+  return (((a | b) & (~size_t(0) << (sizeof(size_t) << 2))) && (t / a != b));
+}
+#endif
+
 // typesafe wrapper around malloc for simple types
 // use free(pointer) to deallocate
 
 template <typename T> T * gralloc(size_t n)
 {
+    size_t total;
+    if (checked_mul(n, sizeof(T), total))
+      return 0;
 #ifdef GRAPHITE2_TELEMETRY
-    telemetry::count_bytes(sizeof(T) * n);
+    telemetry::count_bytes(total);
 #endif
-    return static_cast<T*>(malloc(sizeof(T) * n));
+    return static_cast<T*>(malloc(total));
 }
 
 template <typename T> T * grzeroalloc(size_t n)