Update libcxx and libcxxabi to LLVM 20.1.4 (emscripten-core#24346)

This updates libcxx and libcxxabi to LLVM 20.1.4:
https://github.com/llvm/llvm-project/releases/tag/llvmorg-20.1.4

Before going into each additional change of the PR, these are some
noteworthy changes from this LLVM release:

- Freezing C++03 headers
- RFC:
https://discourse.llvm.org/t/rfc-freezing-c-03-headers-in-libc/77319
  - PRs:
    - llvm/llvm-project#108999
    - llvm/llvm-project#109000
    - llvm/llvm-project#109001
    - llvm/llvm-project#109002
    - 
This copies libc++ headers of the last LLVM 19 release into a separate
directory
(https://github.com/llvm/llvm-project/tree/main/libcxx/include/__cxx03)
and redirects all C++03 workflow there. The motivation is not to fix
C++03 related changes unless they are critical bugs, and simplifies the
main headers. So the main headers are like
  ```
  #if __cplusplus < 201103L && defined(_LIBCPP_USE_FROZEN_CXX03_HEADERS)
  #  include <__cxx03/algorithm>
  #else
  ... main header content ...
  ```

As you can see it looks like we can avoid opting into this by not
defining `_LIBCPP_USE_FROZEN_CXX03_HEADERS` at the moment. I think their
eventual goal is to remove C++03 support from the main headers but it
hasn't seem to have happened yet and I don't know what their timeline
for that is.

Adding that `__cxx03` directory increases the header size by 10MB. We
can get away not using them by not defining
`_LIBCPP_USE_FROZEN_CXX03_HEADERS` in this release, so this update does
not include that directory.

- Sharing of headers between libc++ and libc (Project Hand in Hand)
- RFC:
https://discourse.llvm.org/t/rfc-project-hand-in-hand-llvm-libc-libc-code-sharing/77701
- PR: llvm/llvm-project#91651 (More are likely
to come)

This tries to share some libc headers from libcxx. libcxx's source files
can depend on headers from `libc/shared`, `libc/src/__support`,
`libc/include/llvm-libc-macros`, and `libc/include/llvm-libc-types`. And
it turns out libcxx can also depend on `libc/hdr`, even though the
directory is not in the diagram in the RFC.

These headers can be only included from `libcxx/src` and not
`libcxx/include`, to prevent libcxx's API from changing. So these
headers don't need to be copied into `cache/`.

- Locale API reimplementation
  It doesn't seem to have an RFC, but the PRs are:
  - llvm/llvm-project#113737
  - llvm/llvm-project#115176
  - llvm/llvm-project#115752
  - llvm/llvm-project#122489

It looks this aims provide a new way to define locale API for each
platform. Currently Apple, FreeBSD, MSVCRT, and Fuschia are using the
new API and the others are still using the old one:
https://github.com/llvm/llvm-project/blob/ec28b8f9cc7f2ac187d8a617a6d08d5e56f9120e/libcxx/include/__locale_dir/locale_base_api.h#L116-L138
For our purpose, adding `if defined(__EMSCRIPTEN__)` entry to the list
of "old" list seems to work for the moment, but we may need to move to
the new way eventually later.

---

Additional changes:

- Copy `vendor/llvm/default_assertion_handler.in` to
`__assertion_handler`:
emscripten-core@aa53648
Our previous `__assertion_handler` was copied from
`libcxx/vendor/llvm/default_assertion_handler.in`. This updates our
`__assertion_handler` to the new
`libcxx/vendor/llvm/default_assertion_handler.in`. For what this file
is, see the PR description of emscripten-core#22994, with which the file was added.

- Remove `libcxx/include/__cxx03` directory:
emscripten-core@d646f6b
As I described in "Freezing C++ headers" above, C++03 headers were
copied to `include/cxx03` to be "frozen". But by not defining
`_LIBCPP_USE_FROZEN_CXX03_HEADERS` we can still use the main headers.
This new `__cxx03` header directory is almost 10M and we are not using
it in this update, this deletes it.

- Define more variables in `__config_site`:
emscripten-core@9912236
libcxx decides to almost all configuration macros to be defined. So
before it tested whether a macro was defined/undefined, and now it
assumes it is defined and tests whether its value is 1/0.

Before llvm/llvm-project#112094
`_config_site.in` used to use `#cmakedefine`, which only defined
variables when they were enabled, but now it uses `#cmakedefine01`,
which always defines variables and assigns 1 or 0 depending on whether
the feature is enabled.

So this change adds `#define` to each variable that `_config_site.in`
has an entry of. The value assigned is 1 if it was defined in our
previous Emscripten environment and 0 if not.

- Fix Emscripten's locale:
emscripten-core@2ae01b0
Before, the code was like
https://github.com/emscripten-core/emscripten/blob/dc1abd514b1bade135a01a4453a9ff6def0793b6/system/lib/libcxx/include/__locale_dir/locale_base_api.h#L12-L30
But now they are divided into two parts, one using the new API and the
other using old. See "Locale API reimplementation" above.

https://github.com/llvm/llvm-project/blob/ec28b8f9cc7f2ac187d8a617a6d08d5e56f9120e/libcxx/include/__locale_dir/locale_base_api.h#L116-L138
This adds Emscripten in the beginning of the "old" API list. (This has
to be the beginning; see emscripten-core#23414)

- Import libc headers used by libcxx:
emscripten-core@12a4ee4,
emscripten-core@12a4ee4
and
emscripten-core@43c8ce4
This imports a part of libc headers into `system/lib/llvm-libc`. The
imported directories are:
  - `libc/shared`
  - `libc/src/__support`
  - `libc/include/llvm-libc-macros`
  - `libc/include/llvm-libc-types`
  - `libc/hdr`
  See "sharing of headers between libc+ and libc" above for details.
This also applies llvm/llvm-project#133999,
which is a bugfix that has not be backported, which fixes the bug of
including from a wrong directory.

- `std::uncaught_exception` -> `std::uncaught_exceptions`:
emscripten-core@1bf4e78
`std::uncaught_exception` has been deprecated in C++17, so it generates
a warning (which we treat as an error). Replaced it with
`std::uncaught_exceptions`, which returns the number of uncaught
exceptions (but can still be used as a boolean in the test).

- Remove `ryu_constants.h` and `ryu_long_double_constants.h` from libc:
emscripten-core@5767ac4
These are not used from libcxx and `ryu_long_double_constants.h` is huge
(12M).

Author: aheejin

ChangeLog.md

@@ -20,6 +20,7 @@ See docs/process.md for more on how version tagging works.
 
 4.0.10 (in development)
 ----------------------
+- libcxx and libcxxabi were updated to LLVM 20.1.4. (#24346)
 - The `-sASYNCIFY_LAZY_LOAD_CODE` setting was deprecated.  This setting was
   added as an experiment a long time ago and as far we know has no active users.
   In addition, it cannot work with JSPI (the future of ASYNCIFY). (#24383)

system/lib/libcxx/include/__algorithm/adjacent_find.h

@@ -11,9 +11,9 @@
 #define _LIBCPP___ALGORITHM_ADJACENT_FIND_H
 
 #include <__algorithm/comp.h>
-#include <__algorithm/iterator_operations.h>
 #include <__config>
-#include <__iterator/iterator_traits.h>
+#include <__functional/identity.h>
+#include <__type_traits/invoke.h>
 #include <__utility/move.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
@@ -25,28 +25,30 @@ _LIBCPP_PUSH_MACROS
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-template <class _Iter, class _Sent, class _BinaryPredicate>
-_LIBCPP_NODISCARD _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _Iter
-__adjacent_find(_Iter __first, _Sent __last, _BinaryPredicate&& __pred) {
+template <class _Iter, class _Sent, class _Pred, class _Proj>
+[[__nodiscard__]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _Iter
+__adjacent_find(_Iter __first, _Sent __last, _Pred& __pred, _Proj& __proj) {
   if (__first == __last)
     return __first;
+
   _Iter __i = __first;
   while (++__i != __last) {
-    if (__pred(*__first, *__i))
+    if (std::__invoke(__pred, std::__invoke(__proj, *__first), std::__invoke(__proj, *__i)))
       return __first;
     __first = __i;
   }
   return __i;
 }
 
 template <class _ForwardIterator, class _BinaryPredicate>
-_LIBCPP_NODISCARD inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _ForwardIterator
+[[__nodiscard__]] inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _ForwardIterator
 adjacent_find(_ForwardIterator __first, _ForwardIterator __last, _BinaryPredicate __pred) {
-  return std::__adjacent_find(std::move(__first), std::move(__last), __pred);
+  __identity __proj;
+  return std::__adjacent_find(std::move(__first), std::move(__last), __pred, __proj);
 }
 
 template <class _ForwardIterator>
-_LIBCPP_NODISCARD inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _ForwardIterator
+[[__nodiscard__]] inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _ForwardIterator
 adjacent_find(_ForwardIterator __first, _ForwardIterator __last) {
   return std::adjacent_find(std::move(__first), std::move(__last), __equal_to());
 }

system/lib/libcxx/include/__algorithm/all_of.h

@@ -11,22 +11,32 @@
 #define _LIBCPP___ALGORITHM_ALL_OF_H
 
 #include <__config>
+#include <__functional/identity.h>
+#include <__type_traits/invoke.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-template <class _InputIterator, class _Predicate>
-_LIBCPP_NODISCARD inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 bool
-all_of(_InputIterator __first, _InputIterator __last, _Predicate __pred) {
-  for (; __first != __last; ++__first)
-    if (!__pred(*__first))
+template <class _Iter, class _Sent, class _Proj, class _Pred>
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 bool
+__all_of(_Iter __first, _Sent __last, _Pred& __pred, _Proj& __proj) {
+  for (; __first != __last; ++__first) {
+    if (!std::__invoke(__pred, std::__invoke(__proj, *__first)))
       return false;
+  }
   return true;
 }
 
+template <class _InputIterator, class _Predicate>
+[[__nodiscard__]] inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 bool
+all_of(_InputIterator __first, _InputIterator __last, _Predicate __pred) {
+  __identity __proj;
+  return std::__all_of(__first, __last, __pred, __proj);
+}
+
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP___ALGORITHM_ALL_OF_H

system/lib/libcxx/include/__algorithm/any_of.h

@@ -11,22 +11,32 @@
 #define _LIBCPP___ALGORITHM_ANY_OF_H
 
 #include <__config>
+#include <__functional/identity.h>
+#include <__type_traits/invoke.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-template <class _InputIterator, class _Predicate>
-_LIBCPP_NODISCARD inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 bool
-any_of(_InputIterator __first, _InputIterator __last, _Predicate __pred) {
-  for (; __first != __last; ++__first)
-    if (__pred(*__first))
+template <class _Iter, class _Sent, class _Proj, class _Pred>
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 bool
+__any_of(_Iter __first, _Sent __last, _Pred& __pred, _Proj& __proj) {
+  for (; __first != __last; ++__first) {
+    if (std::__invoke(__pred, std::__invoke(__proj, *__first)))
       return true;
+  }
   return false;
 }
 
+template <class _InputIterator, class _Predicate>
+[[__nodiscard__]] inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 bool
+any_of(_InputIterator __first, _InputIterator __last, _Predicate __pred) {
+  __identity __proj;
+  return std::__any_of(__first, __last, __pred, __proj);
+}
+
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP___ALGORITHM_ANY_OF_H

system/lib/libcxx/include/__algorithm/binary_search.h

@@ -13,7 +13,6 @@
 #include <__algorithm/comp_ref_type.h>
 #include <__algorithm/lower_bound.h>
 #include <__config>
-#include <__iterator/iterator_traits.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
@@ -22,14 +21,14 @@
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 template <class _ForwardIterator, class _Tp, class _Compare>
-_LIBCPP_NODISCARD inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 bool
+[[__nodiscard__]] inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 bool
 binary_search(_ForwardIterator __first, _ForwardIterator __last, const _Tp& __value, _Compare __comp) {
   __first = std::lower_bound<_ForwardIterator, _Tp, __comp_ref_type<_Compare> >(__first, __last, __value, __comp);
   return __first != __last && !__comp(__value, *__first);
 }
 
 template <class _ForwardIterator, class _Tp>
-_LIBCPP_NODISCARD inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 bool
+[[__nodiscard__]] inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 bool
 binary_search(_ForwardIterator __first, _ForwardIterator __last, const _Tp& __value) {
   return std::binary_search(__first, __last, __value, __less<>());
 }

system/lib/libcxx/include/__algorithm/comp.h

@@ -11,6 +11,7 @@
 
 #include <__config>
 #include <__type_traits/desugars_to.h>
+#include <__type_traits/is_integral.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
@@ -44,6 +45,9 @@ struct __less<void, void> {
 template <class _Tp>
 inline const bool __desugars_to_v<__less_tag, __less<>, _Tp, _Tp> = true;
 
+template <class _Tp>
+inline const bool __desugars_to_v<__totally_ordered_less_tag, __less<>, _Tp, _Tp> = is_integral<_Tp>::value;
+
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP___ALGORITHM_COMP_H

system/lib/libcxx/include/__algorithm/comp_ref_type.h

@@ -56,10 +56,10 @@ struct __debug_less {
 // Pass the comparator by lvalue reference. Or in the debug mode, using a debugging wrapper that stores a reference.
 #if _LIBCPP_HARDENING_MODE == _LIBCPP_HARDENING_MODE_DEBUG
 template <class _Comp>
-using __comp_ref_type = __debug_less<_Comp>;
+using __comp_ref_type _LIBCPP_NODEBUG = __debug_less<_Comp>;
 #else
 template <class _Comp>
-using __comp_ref_type = _Comp&;
+using __comp_ref_type _LIBCPP_NODEBUG = _Comp&;
 #endif
 
 _LIBCPP_END_NAMESPACE_STD

system/lib/libcxx/include/__algorithm/copy.h

@@ -11,11 +11,12 @@
 
 #include <__algorithm/copy_move_common.h>
 #include <__algorithm/for_each_segment.h>
-#include <__algorithm/iterator_operations.h>
 #include <__algorithm/min.h>
 #include <__config>
+#include <__iterator/iterator_traits.h>
 #include <__iterator/segmented_iterator.h>
 #include <__type_traits/common_type.h>
+#include <__type_traits/enable_if.h>
 #include <__utility/move.h>
 #include <__utility/pair.h>
 
@@ -28,10 +29,9 @@ _LIBCPP_PUSH_MACROS
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-template <class, class _InIter, class _Sent, class _OutIter>
+template <class _InIter, class _Sent, class _OutIter>
 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_InIter, _OutIter> __copy(_InIter, _Sent, _OutIter);
 
-template <class _AlgPolicy>
 struct __copy_impl {
   template <class _InIter, class _Sent, class _OutIter>
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_InIter, _OutIter>
@@ -47,7 +47,7 @@ struct __copy_impl {
 
   template <class _InIter, class _OutIter>
   struct _CopySegment {
-    using _Traits = __segmented_iterator_traits<_InIter>;
+    using _Traits _LIBCPP_NODEBUG = __segmented_iterator_traits<_InIter>;
 
     _OutIter& __result_;
 
@@ -56,7 +56,7 @@ struct __copy_impl {
 
     _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 void
     operator()(typename _Traits::__local_iterator __lfirst, typename _Traits::__local_iterator __llast) {
-      __result_ = std::__copy<_AlgPolicy>(__lfirst, __llast, std::move(__result_)).second;
+      __result_ = std::__copy(__lfirst, __llast, std::move(__result_)).second;
     }
   };
 
@@ -85,7 +85,7 @@ struct __copy_impl {
     while (true) {
       auto __local_last = _Traits::__end(__segment_iterator);
       auto __size       = std::min<_DiffT>(__local_last - __local_first, __last - __first);
-      auto __iters      = std::__copy<_AlgPolicy>(__first, __first + __size, __local_first);
+      auto __iters      = std::__copy(__first, __first + __size, __local_first);
       __first           = std::move(__iters.first);
 
       if (__first == __last)
@@ -103,17 +103,16 @@ struct __copy_impl {
   }
 };
 
-template <class _AlgPolicy, class _InIter, class _Sent, class _OutIter>
+template <class _InIter, class _Sent, class _OutIter>
 pair<_InIter, _OutIter> inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14
 __copy(_InIter __first, _Sent __last, _OutIter __result) {
-  return std::__copy_move_unwrap_iters<__copy_impl<_AlgPolicy> >(
-      std::move(__first), std::move(__last), std::move(__result));
+  return std::__copy_move_unwrap_iters<__copy_impl>(std::move(__first), std::move(__last), std::move(__result));
 }
 
 template <class _InputIterator, class _OutputIterator>
 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _OutputIterator
 copy(_InputIterator __first, _InputIterator __last, _OutputIterator __result) {
-  return std::__copy<_ClassicAlgPolicy>(__first, __last, __result).second;
+  return std::__copy(__first, __last, __result).second;
 }
 
 _LIBCPP_END_NAMESPACE_STD

system/lib/libcxx/include/__algorithm/copy_backward.h

@@ -13,8 +13,10 @@
 #include <__algorithm/iterator_operations.h>
 #include <__algorithm/min.h>
 #include <__config>
+#include <__iterator/iterator_traits.h>
 #include <__iterator/segmented_iterator.h>
 #include <__type_traits/common_type.h>
+#include <__type_traits/enable_if.h>
 #include <__type_traits/is_constructible.h>
 #include <__utility/move.h>
 #include <__utility/pair.h>

system/lib/libcxx/include/__algorithm/copy_if.h

@@ -10,25 +10,41 @@
 #define _LIBCPP___ALGORITHM_COPY_IF_H
 
 #include <__config>
+#include <__functional/identity.h>
+#include <__type_traits/invoke.h>
+#include <__utility/move.h>
+#include <__utility/pair.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-template <class _InputIterator, class _OutputIterator, class _Predicate>
-inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _OutputIterator
-copy_if(_InputIterator __first, _InputIterator __last, _OutputIterator __result, _Predicate __pred) {
+template <class _InIter, class _Sent, class _OutIter, class _Proj, class _Pred>
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_InIter, _OutIter>
+__copy_if(_InIter __first, _Sent __last, _OutIter __result, _Pred& __pred, _Proj& __proj) {
   for (; __first != __last; ++__first) {
-    if (__pred(*__first)) {
+    if (std::__invoke(__pred, std::__invoke(__proj, *__first))) {
       *__result = *__first;
       ++__result;
     }
   }
-  return __result;
+  return std::make_pair(std::move(__first), std::move(__result));
+}
+
+template <class _InputIterator, class _OutputIterator, class _Predicate>
+inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _OutputIterator
+copy_if(_InputIterator __first, _InputIterator __last, _OutputIterator __result, _Predicate __pred) {
+  __identity __proj;
+  return std::__copy_if(__first, __last, __result, __pred, __proj).second;
 }
 
 _LIBCPP_END_NAMESPACE_STD
 
+_LIBCPP_POP_MACROS
+
 #endif // _LIBCPP___ALGORITHM_COPY_IF_H