Fix OOB write in --print-code.

src/utils.cc

Index: src/utils.cc
diff --git a/src/utils.cc b/src/utils.cc
index 7e8c088dd492dc527e9803204ff6de9b2f5ab7d2..71eaea55d261989a58af4381e20b147fc1b3ddb0 100644
--- a/src/utils.cc
+++ b/src/utils.cc
@@ -46,7 +46,7 @@ void SimpleStringBuilder::AddString(const char* s) {
 
 
 void SimpleStringBuilder::AddSubstring(const char* s, int n) {
-  ASSERT(!is_finalized() && position_ + n < buffer_.length());
+  ASSERT(!is_finalized() && position_ + n <= buffer_.length());
   ASSERT(static_cast<size_t>(n) <= strlen(s));
   memcpy(&buffer_[position_], s, n * kCharSize);
   position_ += n;
@@ -79,7 +79,13 @@ void SimpleStringBuilder::AddDecimalInteger(int32_t value) {
 
 
 char* SimpleStringBuilder::Finalize() {
-  ASSERT(!is_finalized() && position_ < buffer_.length());
+  ASSERT(!is_finalized() && position_ <= buffer_.length());
+  // If there is no space for null termination, overwrite last character.
+  if (position_ == buffer_.length()) {
+    position_--;
+    // Print ellipsis.
+    for (int i = 3; i > 0 && position_ > i; --i) buffer_[position_ - i] = '.';
+  }
   buffer_[position_] = '\0';
   // Make sure nobody managed to add a 0-character to the
   // buffer while building the string.