Skip to content

src: copy-construct data when cloning threadsafe COW #64859

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
Archkon wants to merge 1 commit into
base: main
Choose a base branch
from
+22 −4
Open

src: copy-construct data when cloning threadsafe COW #64859

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
9 changes: 5 additions & 4 deletions src/node_threadsafe_cow-inl.h
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -42,10 +42,11 @@ T* ThreadsafeCopyOnWrite<T>::Write::operator->() {
}

template <typename T>
ThreadsafeCopyOnWrite<T>::Impl::Impl(const Impl& other) {
RwLock::ScopedReadLock lock(other.mutex);
data = other.data;
}
ThreadsafeCopyOnWrite<T>::Impl::Impl(const Impl& other)
: data([&other]() {
RwLock::ScopedReadLock lock(other.mutex);
return other.data;
}()) {}

} // namespace node

Expand Down
17 changes: 17 additions & 0 deletions test/cctest/test_per_process.cc
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -6,6 +6,7 @@

#include <string>

using node::ThreadsafeCopyOnWrite;
using node::builtins::BuiltinLoader;
using node::builtins::BuiltinSourceMap;

Expand All @@ -18,6 +19,22 @@ class PerProcessTest : public ::testing::Test {

namespace {

struct CopyConstructOnly {
explicit CopyConstructOnly(int value) : value(value) {}
CopyConstructOnly() = delete;
CopyConstructOnly(const CopyConstructOnly&) = default;
CopyConstructOnly& operator=(const CopyConstructOnly&) = delete;

int value;
};

TEST(ThreadsafeCopyOnWriteTest, CloneCopyConstructsData) {
const ThreadsafeCopyOnWrite<CopyConstructOnly> original(42);
auto copy = original;

EXPECT_EQ(copy.write()->value, 42);

@Hardanish-Singh Hardanish-Singh Jul 31, 2026

Copy link
Copy Markdown
Contributor

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Optional test improvement

The existing assertion proves cloning succeeded, but the test could additionally demonstrate COW independence:

TEST(ThreadsafeCopyOnWriteTest, CloneCopyConstructsData) {
  const ThreadsafeCopyOnWrite<CopyConstructOnly> original(42);
  auto copy = original;

  copy.write()->value = 43;

  EXPECT_EQ(original.read()->value, 42);
  EXPECT_EQ(copy.read()->value, 43);
}

}

TEST_F(PerProcessTest, EmbeddedSources) {
const auto& sources = PerProcessTest::get_sources_for_test();
ASSERT_TRUE(std::any_of(sources.cbegin(), sources.cend(), [](auto p) {
Expand Down
Loading