[libc++] Make `<map>` `std::map` constexpr as part of P3372R3 #134330

vinay-deshmukh · 2025-04-04T00:41:50Z

Depends on:

Summary:

Apply _LIBCPP_CONSTEXPR_SINCE_CXX26 to map, __tree, node-handle, __libcpp_erase_if, __lazy_synth_three_way_comparator, __lazy_compare_result, libcxx/include/__utility/try_key_extraction.h
Skip test erase_if.pass.cpp for GCC during constant evaluation. AFAICT this appears to be a g++ bug, as the test passes with clang
Disable test for node-handle::key() during constant evaluation (CWG2514). It is annotated with a // FIXME
map.modifiers/try.emplace.pass.cpp : Start using the previously unused mv3. (Should this be a separate patch?)
Has a TODO for multimap and ohters
a. libcxx/test/std/containers/associative/map/map.ops/contains.pass.cpp
b. libcxx/test/std/containers/associative/map/map.ops/contains_transparent.pass.cpp
a. libcxx/test/std/containers/container.node/node_handle.pass.cpp
~~Fix typo in libcxx/include/__memory/pointer_traits.h~~ -> [NFC][libc++] Fix typo in libcxx/include/__memory/pointer_traits.h #157304
pair<const MoveOnly, ...>
a. move_assign.pass.cpp
b. move_alloc.pass.cpp
c. Fails to compile if static_assert(test()); is called in the test file
d. Has a // FIXME with commented code
~~Change __tree_node to construct it's __node_value_type during construction to avoid the: note: member call on object outside its lifetime is not allowed in a constant expression issue.~~ This became -> [libc++] Remove UB from std::__tree_node construction #153908

github-actions · 2025-04-04T00:43:27Z

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github-actions · 2025-04-04T00:44:15Z

✅ With the latest revision this PR passed the C/C++ code formatter.

…__value_type<int, int>')

…P3372-constexpr-map

vinay-deshmukh · 2025-10-02T19:07:23Z

Windows / clang-cl builds are failing due to:

note: non-literal type 'std::__tree_node<std::__value_type<int, double>, void *>' cannot be used in a constant expression

Which may be due to C:/Program Files/Microsoft Visual Studio/2022/Enterprise/VC/Tools/Llvm/x64/bin/clang-cl.exe being an older version (<=19) similar to the arm issue discussed earlier.

This may get fixed by #161736

There's a similar issue for macos builds , which use AppleClang 17.0.0.17000319 which is probably old(er?) than clang 19.x. Not sure who the right person is to ping out that

vinay-deshmukh · 2025-10-04T13:34:46Z

macos builds appear to be failing due to an unrelated issue:

https://github.com/llvm/llvm-project/actions/runs/18238483208/job/51938026500?pr=134330

 # | /Users/runner/work/llvm-project/llvm-project/build/apple-system-hardened/cxx/libcxx/test-suite-install/include/c++/v1/experimental/__simd/vec_ext.h:95:91: error: cannot initialize a member subobject of type '__attribute__((__vector_size__(8 * sizeof(unsigned char)))) unsigned char' (vector of 8 'unsigned char' values) with an rvalue of type '__attribute__((__vector_size__(8 * sizeof(char)))) char' (vector of 8 'char' values)
  # |    95 |   static _LIBCPP_HIDE_FROM_ABI _MaskStorage __negate(_SimdStorage __s) noexcept { return {!__s.__data}; }
  # |       |                                                                                           ^~~~~~~~~~~
  # | /Users/runner/work/llvm-project/llvm-project/build/apple-system-hardened/cxx/libcxx/test-suite-install/include/c++/v1/experimental/__simd/simd.h:134:29: note: in instantiation of member function 'std::experimental::__simd_operations<char, std::experimental::simd_abi::__vec_ext<8>>::__negate' requested here
  # |   134 |     return mask_type(_Impl::__negate(__s_), mask_type::__storage_tag);
  # |       |                             ^
  # | /Users/runner/work/llvm-project/llvm-project/libcxx/test/std/experimental/simd/simd.class/simd_unary.pass.cpp:113:47: note: in instantiation of member function 'std::experimental::simd<char, std::experimental::simd_abi::__vec_ext<8>>::operator!' requested here
  # |   113 |     assert_simd_mask_values_equal<array_size>(!origin_simd, expected_value);
  # |       |                                               ^
  # | /Users/runner/work/llvm-project/llvm-project/libcxx/test/support/type_algorithms.h:52:23: note: in instantiation of function template specialization 'CheckSimdNegationOperator<char, 8>::operator()<std::experimental::simd_abi::__vec_ext<8>>' requested here
  # |    52 |   swallow((f.template operator()<Types>(), 0)...);
  # |       |                       ^
  # | /Users/runner/work/llvm-project/llvm-project/libcxx/test/std/experimental/simd/simd.class/../test_utils.h:40:5: note: in instantiation of function template specialization 'TestAllSimdAbiFunctor<CheckSimdNegationOperator>::instantiate_with_n<char, 1UL, 2UL, 3UL, 4UL, 8UL, 16UL, 30UL, 31UL, 32UL>' requested here
  # |    40 |     instantiate_with_n<T>(
  # |       |     ^
  # | /Users/runner/work/llvm-project/llvm-project/libcxx/test/support/type_algorithms.h:52:23: note: in instantiation of function template specialization 'TestAllSimdAbiFunctor<CheckSimdNegationOperator>::operator()<char>' requested here
  # |    52 |   swallow((f.template operator()<Types>(), 0)...);
  # |       |                       ^
  # | /Users/runner/work/llvm-project/llvm-project/libcxx/test/std/experimental/simd/simd.class/simd_unary.pass.cpp:184:3: note: in instantiation of function template specialization 'test_all_simd_abi<CheckSimdNegationOperator>' requested here
  # |   184 |   test_all_simd_abi<CheckSimdNegationOperator>();
  # |       |   ^
  # | In file included from /Users/runner/work/llvm-project/llvm-project/libcxx/test/std/experimental/simd/simd.class/simd_unary.pass.cpp:30:
  # | In file included from /Users/runner/work/llvm-project/llvm-project/libcxx/test/std/experimental/simd/simd.class/../test_utils.h:15:
  # | In file included from /Users/runner/work/llvm-project/llvm-project/build/apple-system-hardened/cxx/libcxx/test-suite-install/include/c++/v1/experimental/simd:89:

vinay-deshmukh force-pushed the vinay-issue-128660-P3372-constexpr-map branch 2 times, most recently from 46d0bb9 to 9ea718f Compare April 7, 2025 22:25

vinay-deshmukh added 26 commits April 8, 2025 22:42

pass map.modifiers/insert_cv.pass.cpp

9e3fff0

pass map.modifiers/insert_iter_cv.pass.cpp

662d172

pass map.modifiers/insert_iter_rv.pass.cpp

3c39ba7

pass map.modifiers/insert_node_type.pass

a462c8e

pass map.modifiers/insert_node_type_hint.pass.cpp

d57d651

pass map.modifiers/insert_or_assign.pass.cpp

8c94f4d

pass map.modifiers/insert_rv.pass.cpp

dc5fbee

pass map.modifiers/try.emplace.pass.cpp, fix typos

674854d

pass map.nonmember/compare.three_way.pass.cpp

a00a45a

pass map.nonmember/op_compare.pass.cpp

3728788

pass map.observers/key_comp.pass.cpp

490645c

pass map.observers/value_comp.pass.cpp

f136d58

pass map.ops/contains.pass.cpp

bef3a7f

pass map.ops/contains_transparent.pass.cpp

784b1c9

pass map.ops/count.pass.cpp

2b9085b

pass map.ops/count_transparent.pass.cpp

995c23a

pass map.ops/equal_range_transparent.pass.cpp

aba79eb

pass map.special/member_swap.pass.cpp

70f2163

pass map.value_compare/invoke.pass.cpp

f20cfeb

pass map.value_compare/types.pass.cpp

381bd9b

cleanup

b3218a7

Pass compare.pass.cpp

7cfa07f

pass incomplete_type.pass.cpp

7930edd

error: call to deleted constructor of '__node_value_type' (aka 'std::…

2ff98ea

…__value_type<int, int>')

clang-format

27f2bfe

Generate macro version correctly

10f536f

vinay-deshmukh added 11 commits September 30, 2025 19:21

undo previous

c7307a8

unnecessary destructor for __tree_node_base

b556c84

Remove constexpr from cpp03 code

8ecbbb5

Unnecessary annotation on deleted function

2f2bec2

simplify type_trait

2661937

Allow runtime decision for __insert_unique_from_orphaned_node

c28aac0

Allow runtime decision for __assign_value

c448834

local cf

f732308

Simplify at.pass.cpp

d358aed

use TEST_IS_CONSTANT_EVALUATED over libcxx function

986e713

Merge remote-tracking branch 'upstream/main' into vinay-issue-128660-…

5c84f1f

…P3372-constexpr-map

vinay-deshmukh force-pushed the vinay-issue-128660-P3372-constexpr-map branch from 01dc888 to 5c84f1f Compare October 2, 2025 13:30

vinay-deshmukh added 3 commits October 2, 2025 10:52

Remove extra arm CI hack

839c373

missing space

80b2f06

Avoid creating a __tmp

c5d73dd

explicit copy

c4a0092

vinay-deshmukh requested review from philnik777 and frederick-vs-ja October 3, 2025 03:24

Remove constexpr annotations from multimap

d4a0430

mstorsjo mentioned this pull request Oct 3, 2025

[libcxx] [ci] Make the CI find the right version of Clang-cl #161736

Merged

CI fix for clang <=20

87d28d5

This was referenced Oct 3, 2025

[libc++] P3372R3: constexpr multimap #128661

Open

[libc++] Make <map> std::multimap constexpr as part of P3372R3 #161901

Draft

vinay-deshmukh added 3 commits October 3, 2025 20:36

Check clang<20 only for clang based compilers

3193936

Fix apple-clang macro lookup

e93ea65

Fixme, not todo

b2ccf29

Updated FIXME

29acf01

vinay-deshmukh force-pushed the vinay-issue-128660-P3372-constexpr-map branch from ff27195 to 29acf01 Compare October 5, 2025 15:02

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[libc++] Make `<map>` `std::map` constexpr as part of P3372R3 #134330

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