Use mainline Abseil instead of our fork

build/scripts/depsCheck.sh

@@ -124,7 +124,7 @@ function checkTzdb {
 echo
 echo '# depsDownload.sh'
 
-checkGitHubCommit "ABSEIL" "https://github.com/tmbasic-lang/abseil-cpp/commits.atom"
+checkGitHubCommit "ABSEIL" "https://github.com/abseil/abseil-cpp/commits.atom"
 checkGnu "binutils-" "BINUTILS" "https://ftp.gnu.org/gnu/binutils/"
 checkJfrog "BOOST" "https://boostorg.jfrog.io/artifactory/main/release/"
 checkGitHubRelease "CLI11" "https://github.com/CLIUtils/CLI11/releases.atom"

build/scripts/depsDownload.sh

@@ -31,7 +31,7 @@ function downloadFile {
 }
 
 # don't update these versions by hand. instead, run scripts/depsCheck.sh
-ABSEIL_VERSION=7626bacbbc05bfeb03a09e5993934c9d2b80b9ba
+ABSEIL_VERSION=14b8a4eac3e5a7b97ba4cc7b7dadf2a85aae8215
 BINUTILS_VERSION=2.42
 BOOST_VERSION=1.84.0
 CLI11_VERSION=2.4.1

src/test/DateTest.cpp

@@ -28,3 +28,18 @@ TEST(DateTest, DateTimeOffsetPartsRoundTrip) {
     ASSERT_EQ(parts.millisecond, roundTripParts.millisecond);
     ASSERT_EQ(parts.utcOffsetMilliseconds, roundTripParts.utcOffsetMilliseconds);
 }
+
+TEST(DateTest, TestZoneLookup) {
+    vm::initializeTzdb();
+
+    // We support this special time zone so we can recognize when we're using our own static data instead of the system
+    // zoneinfo data.
+    absl::TimeZone tz{};
+    ASSERT_TRUE(absl::LoadTimeZone("tmbasic-dummy-zone", &tz));
+
+    // Make sure LoadTimeZone actually returns false if the zone doesn't exist.
+    ASSERT_FALSE(absl::LoadTimeZone("invalid-time-zone", &tz));
+
+    // Make sure we have a valid zone.
+    ASSERT_TRUE(absl::LoadTimeZone("America/Chicago", &tz));
+}

src/vm/date.cpp

@@ -3,25 +3,82 @@
 #include "shared/tar.h"
 #include "vm/RecordBuilder.h"
 
-// This is tzdb.tar, the contents of /usr/share/zoneinfo.
-extern const char kResourceTzdb[];  // NOLINT(modernize-avoid-c-arrays)
-extern const uint kResourceTzdb_len;
+// We depend on an internal implementation detail of Abseil in order to statically link our own zoneinfo data.
+// However we have evidence that Google uses it in this way, so the risk of breakage should be low.
+// See: https://github.com/abseil/abseil-cpp/pull/1626
+#include <absl/time/internal/cctz/include/cctz/zone_info_source.h>
 
-namespace vm {
+using absl::time_internal::cctz::ZoneInfoSource;
 
 // NOLINTNEXTLINE(cppcoreguidelines-avoid-non-const-global-variables)
 static bool _isTzdbInitialized = false;
 
-// Keep these alive because we have handed out string_views which must remain valid for the life of the program.
-// NOLINTNEXTLINE(cppcoreguidelines-avoid-non-const-global-variables)
-static std::vector<std::vector<char>> _zoneInfoFiles{};
+// An implementation of ZoneInfoSource backed by static in-memory data.
+static std::unordered_map<std::string, std::vector<char>> zoneInfoFiles{};
+
+class StaticZoneInfoSource : public ZoneInfoSource {
+   public:
+    explicit StaticZoneInfoSource(const std::vector<char>& file) : _file(file), _len(file.size()) {}
+
+    std::size_t Read(void* ptr, std::size_t size) override {
+        size = std::min(size, _len);
+        memcpy(ptr, _file.data() + _offset, size);
+        _offset += size;
+        _len -= size;
+        return size;
+    }
+
+    int Skip(std::size_t offset) override {
+        offset = std::min(offset, _len);
+        _offset += offset;
+        _len -= offset;
+        return 0;
+    }
+
+    std::string Version() const override { return std::string(); }
+
+   private:
+    const std::vector<char>& _file;
+    std::size_t _offset = 0;
+    std::size_t _len;
+};
+
+std::unique_ptr<ZoneInfoSource> customZoneInfoSourceFactory(
+    const std::string& name,
+    const std::function<std::unique_ptr<ZoneInfoSource>(const std::string& name)>& fallback_factory) {
+    assert(_isTzdbInitialized);
+
+    // We accept a dummy name as a test that we're using our static data and not the system data.
+    if (name == "tmbasic-dummy-zone") {
+        return customZoneInfoSourceFactory("Etc/GMT-4", fallback_factory);
+    }
+
+    auto it = zoneInfoFiles.find(name);
+    if (it == zoneInfoFiles.end()) {
+        return nullptr;
+    }
+    return std::make_unique<StaticZoneInfoSource>(it->second);
+}
+
+// Abseil will look for this zone_info_source_factory symbol.
+namespace absl {
+namespace time_internal {
+namespace cctz_extension {
+ZoneInfoSourceFactory zone_info_source_factory = customZoneInfoSourceFactory;
+}  // namespace cctz_extension
+}  // namespace time_internal
+}  // namespace absl
+
+// This is tzdb.tar, the contents of /usr/share/zoneinfo.
+extern const char kResourceTzdb[];  // NOLINT(modernize-avoid-c-arrays)
+extern const uint kResourceTzdb_len;
 
 static void addStaticZoneInfoFile(const std::string& name, std::vector<char> data) {
-    const auto& storedData = _zoneInfoFiles.emplace_back(std::move(data));
-    std::string_view sv{ storedData.data(), storedData.size() };
-    absl::LoadStaticZoneInfoFile(name, sv);
+    zoneInfoFiles.emplace(name, std::move(data));
 }
 
+namespace vm {
+
 void initializeTzdb() {
     if (!_isTzdbInitialized) {
         shared::untar(kResourceTzdb, static_cast<size_t>(kResourceTzdb_len), addStaticZoneInfoFile);