[intl] Use std::string backing stores in tz cache

Long timezone names overflowed the timezone cache which had a static
length of 100. This uses dynamically allocated std::strings as backing
stores instead.

Bug: chromium:842085
Cq-Include-Trybots: luci.v8.try:v8_linux_noi18n_rel_ng
Change-Id: I3da474c8b7c530b0933018c6239021979c320043
Reviewed-on: https://chromium-review.googlesource.com/1064111Reviewed-by: Yang Guo <yangguo@chromium.org>
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53243}

src/builtins/builtins-date.cc

@@ -158,11 +158,13 @@ void ToDateString(double time_val, Vector<char> str, DateCache* date_cache,
                kShortMonths[month], day, year);
       return;
     case kTimeOnly:
+      // TODO(842085): str may be silently truncated.
       SNPrintF(str, "%02d:%02d:%02d GMT%c%02d%02d (%s)", hour, min, sec,
                (timezone_offset < 0) ? '-' : '+', timezone_hour, timezone_min,
                local_timezone);
       return;
     case kDateAndTime:
+      // TODO(842085): str may be silently truncated.
       SNPrintF(str, "%s %s %02d %04d %02d:%02d:%02d GMT%c%02d%02d (%s)",
                kShortWeekDays[weekday], kShortMonths[month], day, year, hour,
                min, sec, (timezone_offset < 0) ? '-' : '+', timezone_hour,

src/intl.cc

@@ -358,17 +358,17 @@ ICUTimezoneCache::~ICUTimezoneCache() { Clear(); }
 
 const char* ICUTimezoneCache::LocalTimezone(double time_ms) {
   bool is_dst = DaylightSavingsOffset(time_ms) != 0;
-  char* name = is_dst ? dst_timezone_name_ : timezone_name_;
-  if (name[0] == '\0') {
+  std::string* name = is_dst ? &dst_timezone_name_ : &timezone_name_;
+  if (name->empty()) {
     icu::UnicodeString result;
     GetTimeZone()->getDisplayName(is_dst, icu::TimeZone::LONG, result);
     result += '\0';
 
-    icu::CheckedArrayByteSink byte_sink(name, kMaxTimezoneChars);
+    icu::StringByteSink<std::string> byte_sink(name);
     result.toUTF8(byte_sink);
-    CHECK(!byte_sink.Overflowed());
   }
-  return const_cast<const char*>(name);
+  DCHECK(!name->empty());
+  return name->c_str();
 }
 
 icu::TimeZone* ICUTimezoneCache::GetTimeZone() {
@@ -418,8 +418,8 @@ double ICUTimezoneCache::LocalTimeOffset(double time_ms, bool is_utc) {
 void ICUTimezoneCache::Clear() {
   delete timezone_;
   timezone_ = nullptr;
-  timezone_name_[0] = '\0';
-  dst_timezone_name_[0] = '\0';
+  timezone_name_.clear();
+  dst_timezone_name_.clear();
 }
 
 }  // namespace internal

src/intl.h

@@ -9,6 +9,8 @@
 #ifndef V8_INTL_H_
 #define V8_INTL_H_
 
+#include <string>
+
 #include "src/base/timezone-cache.h"
 #include "src/objects.h"
 #include "src/objects/string.h"
@@ -64,9 +66,8 @@ class ICUTimezoneCache : public base::TimezoneCache {
 
   icu::TimeZone* timezone_;
 
-  static const int32_t kMaxTimezoneChars = 100;
-  char timezone_name_[kMaxTimezoneChars];
-  char dst_timezone_name_[kMaxTimezoneChars];
+  std::string timezone_name_;
+  std::string dst_timezone_name_;
 };
 
 }  // namespace internal