Skip to content

Avoid extra move in box construction #70

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
moskupols wants to merge 2 commits into
base: master
Choose a base branch
from
Open

Avoid extra move in box construction #70

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
2f85010
Avoid constructing temporary T in make_box
moskupols Oct 23, 2025
da75c3b
Add a regression test
moskupols Oct 23, 2025
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
12 changes: 10 additions & 2 deletions include/function2/function2.hpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -376,7 +376,11 @@ struct box : private Allocator {

T value_;

explicit box(T value, Allocator allocator_)
explicit box(const T& value, Allocator allocator_)
: Allocator(std::move(allocator_)), value_(value) {
}

explicit box(T&& value, Allocator allocator_)
: Allocator(std::move(allocator_)), value_(std::move(value)) {
}

Expand All @@ -392,7 +396,11 @@ struct box<false, T, Allocator> : private Allocator {

T value_;

explicit box(T value, Allocator allocator_)
explicit box(const T& value, Allocator allocator_)
: Allocator(std::move(allocator_)), value_(value) {
}

explicit box(T&& value, Allocator allocator_)
: Allocator(std::move(allocator_)), value_(std::move(value)) {
}

Expand Down
41 changes: 41 additions & 0 deletions test/regressions.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -6,6 +6,7 @@

#include <memory>
#include <string>
#include <utility>
#include <vector>

#include "function2-test.hpp"
Expand Down Expand Up @@ -261,3 +262,43 @@ TYPED_TEST(AllReferenceRetConstructTests, reference_returns_not_buildable) {
ref_obj& ref = left();
ASSERT_EQ(ref.data(), 8373827);
}

/// Functor which counts the number of times it has been copied or moved
class CopyAndMoveCountFunctor {
int copy_count = 0;
int move_count = 0;

public:
CopyAndMoveCountFunctor() = default;

CopyAndMoveCountFunctor(const CopyAndMoveCountFunctor& that) {
*this = that;
}

CopyAndMoveCountFunctor& operator=(const CopyAndMoveCountFunctor& that) {
copy_count = that.copy_count + 1;
move_count = that.move_count;
return *this;
}

CopyAndMoveCountFunctor(CopyAndMoveCountFunctor&& that) {
*this = std::move(that);
}

CopyAndMoveCountFunctor& operator=(CopyAndMoveCountFunctor&& that) {
copy_count = that.copy_count;
move_count = that.move_count + 1;
return *this;
}

~CopyAndMoveCountFunctor() = default;

std::pair<int, int> operator()() const {
return std::make_pair(copy_count, move_count);
}
};

TEST(regression_tests, no_extra_move_during_construction) {
fu2::function<std::pair<int, int>()> f(CopyAndMoveCountFunctor{});
ASSERT_EQ(f(), std::make_pair(0, 2));
}