Guard the value suffixes against negative overflow.

The k, m and g guards only checked the positive side, so -4611686018427387904K became 0.

src/rpc/parse.cc

@@ -102,6 +102,12 @@ parse_whole_value_nothrow(const char* src, int64_t* value, int base, int unit) {
   return true;
 }
 
+static bool
+value_fits_shifted(int64_t value, int shift) {
+  return value <= (std::numeric_limits<int64_t>::max() >> shift) &&
+         value >= (std::numeric_limits<int64_t>::min() >> shift);
+}
+
 const char*
 parse_value_nothrow(const char* src, int64_t* value, int base, int unit) {
   if (unit <= 0)
@@ -124,15 +130,15 @@ parse_value_nothrow(const char* src, int64_t* value, int base, int unit) {
   case 'B': ++last; break;
   case 'k':
   case 'K':
-    if (*value > (int64_t)0x1FFFFFFFFFFFFF) return src; // overflow guard
+    if (!value_fits_shifted(*value, 10)) return src; // overflow guard
     *value = *value << 10; ++last; break;
   case 'm':
   case 'M':
-    if (*value > (int64_t)0x7FFFFFFFFFF) return src; // overflow guard
+    if (!value_fits_shifted(*value, 20)) return src; // overflow guard
     *value = *value << 20; ++last; break;
   case 'g':
   case 'G':
-    if (*value > (int64_t)0x1FFFFFFFF) return src; // overflow guard
+    if (!value_fits_shifted(*value, 30)) return src; // overflow guard
     *value = *value << 30; ++last; break;
 //   case ' ':
 //   case '\0': *value = *value * unit; break;