[libcxx-commits] [libcxx] [libc++] Improve the test coverage for std::vector::emplace (PR #132440)
Peng Liu via libcxx-commits
libcxx-commits at lists.llvm.org
Thu Mar 27 09:27:06 PDT 2025
================
@@ -7,150 +7,341 @@
//===----------------------------------------------------------------------===//
// UNSUPPORTED: c++03 && !stdlib=libc++
+// ADDITIONAL_COMPILE_FLAGS(has-fconstexpr-steps): -fconstexpr-steps=9000000
// <vector>
// template <class... Args> iterator emplace(const_iterator pos, Args&&... args);
-#include <vector>
#include <cassert>
+#include <cstddef>
+#include <type_traits>
+#include <utility>
+#include <vector>
-#include "test_macros.h"
-#include "test_allocator.h"
-#include "min_allocator.h"
#include "asan_testing.h"
+#include "common.h"
+#include "min_allocator.h"
+#include "test_allocator.h"
+#include "test_macros.h"
-class A {
- int i_;
- double d_;
+struct MoveOnly {
+ int value;
- A(const A&);
- A& operator=(const A&);
+ TEST_CONSTEXPR_CXX14 explicit MoveOnly(int i) : value(i) {}
-public:
- TEST_CONSTEXPR_CXX14 A(int i, double d) : i_(i), d_(d) {}
+ MoveOnly(MoveOnly const&) = delete;
+ MoveOnly& operator=(MoveOnly const&) = delete;
- TEST_CONSTEXPR_CXX14 A(A&& a) : i_(a.i_), d_(a.d_) {
- a.i_ = 0;
- a.d_ = 0;
- }
+ TEST_CONSTEXPR_CXX14 MoveOnly(MoveOnly&& other) TEST_NOEXCEPT : value(other.value) { other.value = -1; }
- TEST_CONSTEXPR_CXX14 A& operator=(A&& a) {
- i_ = a.i_;
- d_ = a.d_;
- a.i_ = 0;
- a.d_ = 0;
+ TEST_CONSTEXPR_CXX14 MoveOnly& operator=(MoveOnly&& other) TEST_NOEXCEPT {
+ value = other.value;
+ other.value = -1;
return *this;
}
- TEST_CONSTEXPR_CXX14 int geti() const { return i_; }
- TEST_CONSTEXPR_CXX14 double getd() const { return d_; }
+ TEST_CONSTEXPR_CXX14 friend bool operator==(MoveOnly const& lhs, MoveOnly const& rhs) {
+ return lhs.value == rhs.value;
+ }
};
-TEST_CONSTEXPR_CXX20 bool tests() {
+template <class T>
+struct has_moved_from_sentinel : std::false_type {};
+
+template <>
+struct has_moved_from_sentinel<MoveOnly> : std::true_type {};
+
+template <template <class...> class Allocator, class T>
+TEST_CONSTEXPR_CXX20 void test() {
+ using Vector = std::vector<T, Allocator<T> >;
+ using Iterator = typename Vector::iterator;
+
+ // Check the return type
{
- std::vector<A> c;
- std::vector<A>::iterator i = c.emplace(c.cbegin(), 2, 3.5);
- assert(i == c.begin());
- assert(c.size() == 1);
- assert(c.front().geti() == 2);
- assert(c.front().getd() == 3.5);
- assert(is_contiguous_container_asan_correct(c));
- i = c.emplace(c.cend(), 3, 4.5);
- assert(i == c.end() - 1);
- assert(c.size() == 2);
- assert(c.front().geti() == 2);
- assert(c.front().getd() == 3.5);
- assert(c.back().geti() == 3);
- assert(c.back().getd() == 4.5);
- assert(is_contiguous_container_asan_correct(c));
- i = c.emplace(c.cbegin() + 1, 4, 6.5);
- assert(i == c.begin() + 1);
- assert(c.size() == 3);
- assert(c.front().geti() == 2);
- assert(c.front().getd() == 3.5);
- assert(c[1].geti() == 4);
- assert(c[1].getd() == 6.5);
- assert(c.back().geti() == 3);
- assert(c.back().getd() == 4.5);
- assert(is_contiguous_container_asan_correct(c));
+ Vector v;
+ ASSERT_SAME_TYPE(decltype(v.emplace(v.cbegin(), 1)), Iterator);
}
+
+ // Emplace at the end of a vector with increasing size
{
- std::vector<A, limited_allocator<A, 7> > c;
- std::vector<A, limited_allocator<A, 7> >::iterator i = c.emplace(c.cbegin(), 2, 3.5);
- assert(i == c.begin());
- assert(c.size() == 1);
- assert(c.front().geti() == 2);
- assert(c.front().getd() == 3.5);
- assert(is_contiguous_container_asan_correct(c));
- i = c.emplace(c.cend(), 3, 4.5);
- assert(i == c.end() - 1);
- assert(c.size() == 2);
- assert(c.front().geti() == 2);
- assert(c.front().getd() == 3.5);
- assert(c.back().geti() == 3);
- assert(c.back().getd() == 4.5);
- assert(is_contiguous_container_asan_correct(c));
- i = c.emplace(c.cbegin() + 1, 4, 6.5);
- assert(i == c.begin() + 1);
- assert(c.size() == 3);
- assert(c.front().geti() == 2);
- assert(c.front().getd() == 3.5);
- assert(c[1].geti() == 4);
- assert(c[1].getd() == 6.5);
- assert(c.back().geti() == 3);
- assert(c.back().getd() == 4.5);
- assert(is_contiguous_container_asan_correct(c));
+ Vector v;
+
+ // starts with size 0
+ {
+ Iterator it = v.emplace(v.cend(), 0);
+ assert(it == v.end() - 1);
+ assert(v.size() == 1);
+ assert(v[0] == T(0));
+ assert(is_contiguous_container_asan_correct(v));
+ }
+
+ // starts with size 1
+ {
+ Iterator it = v.emplace(v.cend(), 1);
+ assert(it == v.end() - 1);
+ assert(v.size() == 2);
+ assert(v[0] == T(0));
+ assert(v[1] == T(1));
+ assert(is_contiguous_container_asan_correct(v));
+ }
+
+ // starts with size 2
+ {
+ Iterator it = v.emplace(v.cend(), 2);
+ assert(it == v.end() - 1);
+ assert(v.size() == 3);
+ assert(v[0] == T(0));
+ assert(v[1] == T(1));
+ assert(v[2] == T(2));
+ assert(is_contiguous_container_asan_correct(v));
+ }
+
+ // starts with size n...
+ for (std::size_t n = 3; n != 100; ++n) {
+ Iterator it = v.emplace(v.cend(), n);
+ assert(it == v.end() - 1);
+ assert(v.size() == n + 1);
+ for (std::size_t i = 0; i != n + 1; ++i)
+ assert(v[i] == T(i));
+ assert(is_contiguous_container_asan_correct(v));
+ }
}
+
+ // Emplace at the start of a vector with increasing size
{
- std::vector<A, min_allocator<A> > c;
- std::vector<A, min_allocator<A> >::iterator i = c.emplace(c.cbegin(), 2, 3.5);
- assert(i == c.begin());
- assert(c.size() == 1);
- assert(c.front().geti() == 2);
- assert(c.front().getd() == 3.5);
- i = c.emplace(c.cend(), 3, 4.5);
- assert(i == c.end() - 1);
- assert(c.size() == 2);
- assert(c.front().geti() == 2);
- assert(c.front().getd() == 3.5);
- assert(c.back().geti() == 3);
- assert(c.back().getd() == 4.5);
- i = c.emplace(c.cbegin() + 1, 4, 6.5);
- assert(i == c.begin() + 1);
- assert(c.size() == 3);
- assert(c.front().geti() == 2);
- assert(c.front().getd() == 3.5);
- assert(c[1].geti() == 4);
- assert(c[1].getd() == 6.5);
- assert(c.back().geti() == 3);
- assert(c.back().getd() == 4.5);
+ Vector v;
+
+ // starts with size 0
+ {
+ Iterator it = v.emplace(v.cbegin(), 0);
+ assert(it == v.begin());
+ assert(v.size() == 1);
+ assert(v[0] == T(0));
+ assert(is_contiguous_container_asan_correct(v));
+ }
+
+ // starts with size 1
+ {
+ Iterator it = v.emplace(v.cbegin(), 1);
+ assert(it == v.begin());
+ assert(v.size() == 2);
+ assert(v[0] == T(1));
+ assert(v[1] == T(0));
+ assert(is_contiguous_container_asan_correct(v));
+ }
+
+ // starts with size 2
+ {
+ Iterator it = v.emplace(v.cbegin(), 2);
+ assert(it == v.begin());
+ assert(v.size() == 3);
+ assert(v[0] == T(2));
+ assert(v[1] == T(1));
+ assert(v[2] == T(0));
+ assert(is_contiguous_container_asan_correct(v));
+ }
+
+ // starts with size n...
+ for (std::size_t n = 3; n != 100; ++n) {
+ Iterator it = v.emplace(v.cbegin(), n);
+ assert(it == v.begin());
+ assert(v.size() == n + 1);
+ for (std::size_t i = 0; i != n + 1; ++i)
+ assert(v[i] == T(n - i));
+ assert(is_contiguous_container_asan_correct(v));
+ }
}
+
+ // Emplace somewhere inside the vector
{
- std::vector<A, safe_allocator<A> > c;
- std::vector<A, safe_allocator<A> >::iterator i = c.emplace(c.cbegin(), 2, 3.5);
- assert(i == c.begin());
- assert(c.size() == 1);
- assert(c.front().geti() == 2);
- assert(c.front().getd() == 3.5);
- i = c.emplace(c.cend(), 3, 4.5);
- assert(i == c.end() - 1);
- assert(c.size() == 2);
- assert(c.front().geti() == 2);
- assert(c.front().getd() == 3.5);
- assert(c.back().geti() == 3);
- assert(c.back().getd() == 4.5);
- i = c.emplace(c.cbegin() + 1, 4, 6.5);
- assert(i == c.begin() + 1);
- assert(c.size() == 3);
- assert(c.front().geti() == 2);
- assert(c.front().getd() == 3.5);
- assert(c[1].geti() == 4);
- assert(c[1].getd() == 6.5);
- assert(c.back().geti() == 3);
- assert(c.back().getd() == 4.5);
+ Vector v;
+ v.emplace_back(0);
+ v.emplace_back(1);
+ v.emplace_back(2);
+ // vector is {0, 1, 2}
+
+ {
+ Iterator it = v.emplace(v.cbegin() + 1, 3);
+ // vector is {0, 3, 1, 2}
+ assert(it == v.begin() + 1);
+ assert(v.size() == 4);
+ assert(v[0] == T(0));
+ assert(v[1] == T(3));
+ assert(v[2] == T(1));
+ assert(v[3] == T(2));
+ assert(is_contiguous_container_asan_correct(v));
+ }
+
+ {
+ Iterator it = v.emplace(v.cbegin() + 2, 4);
+ // vector is {0, 3, 4, 1, 2}
+ assert(it == v.begin() + 2);
+ assert(v.size() == 5);
+ assert(v[0] == T(0));
+ assert(v[1] == T(3));
+ assert(v[2] == T(4));
+ assert(v[3] == T(1));
+ assert(v[4] == T(2));
+ assert(is_contiguous_container_asan_correct(v));
+ }
}
+ // Emplace after reserving
+ {
+ Vector v;
+ v.emplace_back(0);
+ v.emplace_back(1);
+ v.emplace_back(2);
+ // vector is {0, 1, 2}
+
+ v.reserve(1000);
+ Iterator it = v.emplace(v.cbegin() + 1, 3);
+ assert(it == v.begin() + 1);
+ assert(v.size() == 4);
+ assert(v[0] == T(0));
+ assert(v[1] == T(3));
+ assert(v[2] == T(1));
+ assert(v[3] == T(2));
+ assert(is_contiguous_container_asan_correct(v));
+ }
+
+ // Emplace with the same type that's stored in the vector (as opposed to just constructor arguments)
+ {
+ Vector v;
+ Iterator it = v.emplace(v.cbegin(), T(1));
+ assert(it == v.begin());
+ assert(v.size() == 1);
+ assert(v[0] == T(1));
+ assert(is_contiguous_container_asan_correct(v));
+ }
+
+ // Emplace from an element inside the vector itself. This is interesting for two reasons. First, if the
+ // vector must increase capacity, the implementation needs to make sure that it doesn't end up inserting
+ // from a dangling reference.
+ //
+ // Second, if the vector doesn't need to grow but its elements get shifted internally, the implementation
+ // must make sure that it doesn't end up inserting from an element whose position has changed.
+ {
+ // When capacity must increase
+ {
+ Vector v;
+ v.emplace_back(0);
+ v.emplace_back(1);
+
+ while (v.size() < v.capacity()) {
+ v.emplace_back(2);
+ }
+ assert(v.size() == v.capacity());
+ // vector is {0, 1, 2...}
+
+ std::size_t old_cap = v.capacity();
+ v.emplace(v.cbegin(), std::move(v[1]));
+ assert(v.capacity() > old_cap); // test the test
+
+ // vector is {1, 0, -1, 2...}
+ // Note that old v[1] has been set to -1 when it was moved-from
+ assert(v.size() >= 3);
+ assert(v[0] == T(1));
+ assert(v[1] == T(0));
+ if (has_moved_from_sentinel<T>::value)
+ assert(v[2] == T(-1));
+ assert(is_contiguous_container_asan_correct(v));
+ }
+
+ // When elements shift around
+ {
+ Vector v;
+ v.emplace_back(0);
+ v.emplace_back(1);
+ // vector is {0, 1}
+
+ v.reserve(3);
+ std::size_t old_cap = v.capacity();
+ v.emplace(v.cbegin(), std::move(v[1]));
+ assert(v.capacity() == old_cap); // test the test
+
+ // vector is {1, 0, -1}
+ // Note that old v[1] has been set to -1 when it was moved-from
+ assert(v.size() == 3);
+ assert(v[0] == T(1));
+ assert(v[1] == T(0));
+ if (has_moved_from_sentinel<T>::value)
+ assert(v[2] == T(-1));
+ assert(is_contiguous_container_asan_correct(v));
+ }
+ }
+
+ // Make sure that we don't reallocate when we have sufficient capacity
+ {
+ Vector v;
+ v.reserve(8);
+ assert(v.capacity() >= 8);
+
+ std::size_t old_capacity = v.capacity();
+ v.emplace_back(0);
+ v.emplace_back(1);
+ v.emplace_back(2);
+ v.emplace_back(3);
+ assert(v.capacity() == old_capacity);
+
+ v.emplace(v.cend(), 4);
+ assert(v.size() == 5);
+ assert(v.capacity() == old_capacity);
----------------
winner245 wrote:
Ah, I see. I missed the `&&` part. Thanks for clarification. With this note regarding reallocation, I am totally fine with the test now.
https://github.com/llvm/llvm-project/pull/132440
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