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<flat_meow>: Remove FIXME comments, add _Clear_guard to erase(), test more ctors #6040

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Merged
Stephan T. Lavavej (StephanTLavavej) merged 4 commits into from
Jan 23, 2026
Merged

<flat_meow>: Remove FIXME comments, add _Clear_guard to erase(), test more ctors #6040

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a6d279c
Remove FIXME comment: `empty()` is superior to `begin() == end()`, wh…
StephanTLavavej Jan 22, 2026
7d4136c
Remove FIXME comments about heterogeneous insertion.
StephanTLavavej Jan 22, 2026
650bc25
Remove FIXME comment about `erase()`, add `_Clear_guard`s and comments.
StephanTLavavej Jan 22, 2026
3ee6b04
Remove FIXME comment, test remaining constructors.
StephanTLavavej Jan 22, 2026
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4 changes: 3 additions & 1 deletion stl/inc/flat_map
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Original file line number Diff line number Diff line change
Expand Up @@ -1099,7 +1099,7 @@ private:
}

void _Make_invariants_fulfilled() {
if (empty()) { // FIXME maybe consider if (begin() == end()) for consistency with flat_set
if (empty()) {
return;
}

Expand Down Expand Up @@ -1130,6 +1130,8 @@ private:

void _Erase_dupes_if_not_multi() {
if constexpr (_IsUnique) {
// No _Clear_guard needed. The only callers are _Insert_range() (which has a _Clear_guard)
// and _Make_invariants_fulfilled() (which is called only by constructors).
auto _Sorted_view = _View_to_mutate();
const auto _New_last = _RANGES unique(_Sorted_view, _Erase_dupes_if_not_multi_pred()).begin();

Expand Down
24 changes: 15 additions & 9 deletions stl/inc/flat_set
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Expand Up @@ -377,12 +377,12 @@ public:
_Guard._Target = nullptr;
}

// FIXME, the "erase" member functions need clear guards to restore the invariant when the underlying
// container doesn't provide the strong guarantee for its "erase" member functions.

// NB: `erase(iterator)` is identical to `erase(const_iterator)`
iterator erase(const const_iterator _Where) {
return _Mycont.erase(_Where);
_Clear_guard _Guard{this};
const auto _Ret = _Mycont.erase(_Where);
_Guard._Target = nullptr;
return _Ret;
}
size_type erase(const _Kty& _Val) {
return _Erase(_Val);
Expand All @@ -393,7 +393,10 @@ public:
return _Erase(_Val);
}
iterator erase(const const_iterator _First, const const_iterator _Last) {
return _Mycont.erase(_First, _Last);
_Clear_guard _Guard{this};
const auto _Ret = _Mycont.erase(_First, _Last);
_Guard._Target = nullptr;
return _Ret;
}

void swap(_Derived& _Other) noexcept(is_nothrow_swappable_v<_Container> && is_nothrow_swappable_v<_Keylt>) {
Expand Down Expand Up @@ -536,8 +539,6 @@ private:
return pair{_STD _Emplace_with_clear_guard(_Mycont, _Where, _STD forward<_Ty>(_Val)), true};
} else {
// heterogeneous insertion
// FIXME: The standard only requires `find(_Val) == find(_Keyval)` (per N4958 [flat.set.modifiers]/2),
// which cannot guarantee `_Can_insert(_Where, _Keyval)`.
_STL_INTERNAL_STATIC_ASSERT(_Transparent<key_compare> && is_constructible_v<_Kty, _Ty>);
_Kty _Keyval(_STD forward<_Ty>(_Val));
_STL_ASSERT(_Can_insert(_Where, _Keyval),
Expand Down Expand Up @@ -580,8 +581,6 @@ private:
return _STD _Emplace_with_clear_guard(_Mycont, _Where, _STD forward<_Ty>(_Val));
} else {
// heterogeneous insertion
// FIXME: The standard only requires `find(_Val) == find(_Keyval)` (per N4958 [flat.set.modifiers]/2),
// which cannot guarantee `_Can_insert(_Where, _Keyval)`.
_STL_INTERNAL_STATIC_ASSERT(_Transparent<key_compare> && is_constructible_v<_Kty, _Ty>);
_Kty _Keyval(_STD forward<_Ty>(_Val));
_STL_ASSERT(_Can_insert(_Where, _Keyval),
Expand Down Expand Up @@ -640,15 +639,19 @@ private:
if constexpr (_IsUnique && is_same_v<_Ty, key_type>) { // Optimization restricted due to GH-5992
const const_iterator _Where = lower_bound(_Val);
if (_Where != cend() && !_Compare(_Val, *_Where)) {
_Clear_guard _Guard{this};
_Mycont.erase(_Where);
_Guard._Target = nullptr;
return 1;
}
return 0;
} else {
const auto [_First, _Last] = equal_range(_Val);

const auto _Removed = static_cast<size_type>(_Last - _First);
_Clear_guard _Guard{this};
_Mycont.erase(_First, _Last);
_Guard._Target = nullptr;
return _Removed;
}
}
Expand Down Expand Up @@ -717,6 +720,9 @@ private:

void _Erase_dupes_if_not_multi() {
if constexpr (_IsUnique) {
// No _Clear_guard needed. The only callers are _Restore_invariants_after_insert() (which is called
// only by _Insert_range() which has a _Clear_guard) and _Make_invariants_fulfilled() (which is called
// only by constructors which don't need guards and operator=() which has a _Clear_guard).
const auto _End = _Mycont.end();
_Mycont.erase(_STD unique(_Mycont.begin(), _End, _Erase_dupes_if_not_multi_pred()), _End);
}
Expand Down
96 changes: 92 additions & 4 deletions tests/std/tests/P0429R9_flat_map/test.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -14,6 +14,7 @@
#include <print>
#include <ranges>
#include <type_traits>
#include <utility>
#include <vector>

#include <test_container_requirements.hpp>
Expand Down Expand Up @@ -278,9 +279,36 @@ void test_construction() {
}
}
{
// Test flat_map(key_cont, mapped_cont, comp = key_comp())
// Test flat_map(const alloc&)
// and flat_map(const key_comp&, const alloc&)
{
MyAllocatorCounter allocation_counter;
flat_map<int, int> fmap(MyAllocator<int>{});
assert(!allocation_counter.check_then_reset());
flat_map<int, int> fmap1(less<int>{}, MyAllocator<int>{});
assert(!allocation_counter.check_then_reset());

assert(check_key_content(fmap, {}));
assert(check_value_content(fmap, {}));
assert(fmap == fmap1);
}
{
MyAllocatorCounter allocation_counter;
flat_multimap<int, int> fmmap(MyAllocator<int>{});
assert(!allocation_counter.check_then_reset());
flat_multimap<int, int> fmmap1(less<int>{}, MyAllocator<int>{});
assert(!allocation_counter.check_then_reset());

assert(check_key_content(fmmap, {}));
assert(check_value_content(fmmap, {}));
assert(fmmap == fmmap1);
}
}
{
KeyCont<int> keys = {0, 1, 2, 3, 4, 2};
MappedCont<int> vals = {44, 2324, 635462, 433, 5, 7};

// Test flat_map(key_cont, mapped_cont, comp = key_comp())
{
flat_map fmap(keys, vals);
flat_map fmap1(keys, vals, less<int>{});
Expand All @@ -302,12 +330,39 @@ void test_construction() {
}));
assert(fmmap == fmmap1);
}

// Test flat_map(const flat_map&)
// and flat_map(flat_map&&)
{
flat_map fmap(keys, vals);
flat_map fmap1(fmap);
flat_map fmap2(move(fmap));

assert(check_key_content(fmap1, {0, 1, 2, 3, 4}));
assert(check_value_content(fmap1, {44, 2324, 635462, 433, 5}));
assert(fmap1 == fmap2);
}
{
flat_multimap fmmap(keys, vals);
flat_multimap fmmap1(fmmap);
flat_multimap fmmap2(move(fmmap));

assert(check_key_content(fmmap1, {0, 1, 2, 2, 3, 4}));
assert(check_value_content(fmmap1, {44, 2324, 635462, 7, 433, 5},
{
{0, 1, subrange_type::equal},
{2, 3, subrange_type::permutation},
{4, 5, subrange_type::equal},
}));
assert(fmmap1 == fmmap2);
}
}
{
// Test flat_map(const key_cont&, const mapped_cont&, const key_comp&, const alloc&)
// and flat_map(const key_cont&, const mapped_cont&, const alloc&)
KeyCont<int, MyAllocator<int>> keys = {0, 1, 2, 3, 4, 2};
MappedCont<int, MyAllocator<int>> vals = {44, 2324, 635462, 433, 5, 7};

// Test flat_map(const key_cont&, const mapped_cont&, const key_comp&, const alloc&)
// and flat_map(const key_cont&, const mapped_cont&, const alloc&)
{
MyAllocatorCounter allocation_counter;
flat_map fmap(keys, vals, MyAllocator<int>{});
Expand Down Expand Up @@ -335,6 +390,40 @@ void test_construction() {
}));
assert(fmmap == fmmap1);
}

// Test flat_map(const flat_map&, const alloc&)
// and flat_map(flat_map&&, const alloc&)
{
MyAllocatorCounter allocation_counter;
flat_map fmap(keys, vals, MyAllocator<int>{});
assert(allocation_counter.check_then_reset());
flat_map fmap1(fmap);
assert(allocation_counter.check_then_reset());
flat_map fmap2(move(fmap));
assert(!allocation_counter.check_then_reset());

assert(check_key_content(fmap1, {0, 1, 2, 3, 4}));
assert(check_value_content(fmap1, {44, 2324, 635462, 433, 5}));
assert(fmap1 == fmap2);
}
{
MyAllocatorCounter allocation_counter;
flat_multimap fmmap(keys, vals, MyAllocator<int>{});
assert(allocation_counter.check_then_reset());
flat_multimap fmmap1(fmmap);
assert(allocation_counter.check_then_reset());
flat_multimap fmmap2(move(fmmap));
assert(!allocation_counter.check_then_reset());

assert(check_key_content(fmmap1, {0, 1, 2, 2, 3, 4}));
assert(check_value_content(fmmap1, {44, 2324, 635462, 7, 433, 5},
{
{0, 1, subrange_type::equal},
{2, 3, subrange_type::permutation},
{4, 5, subrange_type::equal},
}));
assert(fmmap1 == fmmap2);
}
}
{
// Test flat_map(_Sorted_t, key_cont, mapped_cont, comp = key_comp())
Expand Down Expand Up @@ -667,7 +756,6 @@ void test_construction() {
assert(fmmap == fmmap1);
}
}
// FIXME, verify that all flat_map and flat_multimap constructors are tested
{
PackagedCompare<int> comp;
{
Expand Down