[libc++] Move constexpr <cstring> functions into their own headers and remove unused <cstring> includes

[philnik]

Generate files

[philnik]

Try to fix CI

[philnik]

Try to fix CI

[Mordante]

LGTM, modulo the naming of the file.

libcxx/include/__string/constexpr_c_functions.h

11

I would name the file constexpr_c_functions.h, these are all private functions and not C functions, so the current name is slightly misleading.

libcxx/test/libcxx/transitive_includes/cxx20.csv

341

Since <format> isn't stable yet, I agree this is fine.

[philnik]

libcxx/include/__string/constexpr_c_functions.h

11

I'm a bit confused. I guess you would like a different name, but your suggestion is identical to the current name. Did you forget to replace the name?

[ldionne]

LGTM, please make sure Mark didn't have another name in mind. I personally am fine with this name or any other reasonable name.

[Mordante]

libcxx/include/__string/constexpr_c_functions.h

11

I'm a bit confused. I guess you would like a different name, but your suggestion is identical to the current name. Did you forget to replace the name?

Copy-paste error ;-)

I would name the file constexpr_functions.h, these are all private functions and not C functions, so the current name is slightly misleading.

[philnik]

libcxx/include/__string/constexpr_c_functions.h

11

I see your point, but I think constexpr_functions.h is very open. If you just read the name you would ask "What functions?". Although I admit that you could also read constexpr_c_functions.h as "all the C functions that are constexpr", I think it's closer to a good name. In case anybody has other suggestions we can still rename the file later.

[philnik]

Try to fix CI

[philnik]

Try to fix CI

[philnik]

Try to fix CI

[philnik]

Next try

libcxx/docs/ReleaseNotes.rst

 
 Deprecations and Removals
 -------------------------
 
 - The ``<experimental/coroutine>`` header has been removed in this release. The ``<coroutine>`` header
   has been shipping since LLVM 14, so the Coroutines TS implementation is being removed per our policy
   for removing TSes.
 
+- Several incidental transitive includes have been removed from libc++. Those
+  includes are removed based on the language version used. Incidental transitive
+  inclusions of the following headers have been removed:
+
+  - C++2b: ``cstring``
+
 Upcoming Deprecations and Removals
 ----------------------------------
 
 - The ``_LIBCPP_AVAILABILITY_CUSTOM_VERBOSE_ABORT_PROVIDED`` macro will not be honored anymore in LLVM 18.
   Please see the updated documentation about the safe libc++ mode and in particular the ``_LIBCPP_VERBOSE_ABORT``
   macro for details.
 
 API Changes
 -----------
 
 ABI Affecting Changes
 ---------------------
 
 Build System Changes
 --------------------

libcxx/include/CMakeLists.txt

set(files
   __ranges/take_while_view.h
   __ranges/transform_view.h
   __ranges/view_interface.h
   __ranges/views.h
   __ranges/zip_view.h
   __split_buffer
   __std_stream
   __string/char_traits.h
+  __string/constexpr_c_functions.h
   __string/extern_template_lists.h
   __support/android/locale_bionic.h
   __support/fuchsia/xlocale.h
   __support/ibm/gettod_zos.h
   __support/ibm/locale_mgmt_zos.h
   __support/ibm/nanosleep.h
   __support/ibm/xlocale.h
   __support/musl/xlocale.h

libcxx/include/__bit_reference

 #include <__algorithm/fill_n.h>
 #include <__algorithm/min.h>
 #include <__bit/countr.h>
 #include <__bit/popcount.h>
 #include <__config>
 #include <__iterator/iterator_traits.h>
 #include <__memory/construct_at.h>
 #include <__memory/pointer_traits.h>
-#include <cstring>
 #include <type_traits>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
 _LIBCPP_PUSH_MACROS
 #include <__undef_macros>

libcxx/include/__format/format_arg_store.h

 #endif
 
 #include <__concepts/arithmetic.h>
 #include <__concepts/same_as.h>
 #include <__config>
 #include <__format/concepts.h>
 #include <__format/format_arg.h>
 #include <__utility/forward.h>
-#include <cstring>
 #include <string>
 #include <string_view>
 #include <type_traits>
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 #if _LIBCPP_STD_VER > 17
 

libcxx/include/__hash_table

 #include <__memory/swap_allocator.h>
 #include <__memory/unique_ptr.h>
 #include <__type_traits/can_extract_key.h>
 #include <__utility/forward.h>
 #include <__utility/move.h>
 #include <__utility/pair.h>
 #include <__utility/swap.h>
 #include <cmath>
-#include <cstring>
 #include <initializer_list>
 #include <type_traits>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
 _LIBCPP_PUSH_MACROS

libcxx/include/__string/char_traits.h

 #include <__algorithm/fill_n.h>
 #include <__algorithm/find_end.h>
 #include <__algorithm/find_first_of.h>
 #include <__algorithm/min.h>
 #include <__compare/ordering.h>
 #include <__config>
 #include <__functional/hash.h>
 #include <__iterator/iterator_traits.h>
+#include <__string/constexpr_c_functions.h>
 #include <__type_traits/is_constant_evaluated.h>
 #include <cstddef>
 #include <cstdint>
 #include <cstdio>
-#include <cstring>
 #include <iosfwd>
 
 #ifndef _LIBCPP_HAS_NO_WIDE_CHARACTERS
 #   include <cwchar> // for wmemcpy
 #endif
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header

libcxx/include/__string/constexpr_c_functions.h

+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___STRING_CONSTEXPR_C_FUNCTIONS_H
+#define _LIBCPP___STRING_CONSTEXPR_C_FUNCTIONS_H
+
+#include <__config>
+#include <cstddef>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 size_t __constexpr_strlen(const char* __str) {
+  // GCC currently doesn't support __builtin_strlen for heap-allocated memory during constant evaluation.
+  // https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70816
+#ifdef _LIBCPP_COMPILER_GCC
+  if (__libcpp_is_constant_evaluated()) {
+    size_t __i = 0;
+    for (; __str[__i] != '\0'; ++__i)
+      ;
+    return __i;
+  }
+#endif
+  return __builtin_strlen(__str);
+}
+
+template <class _Tp>
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 int
+__constexpr_memcmp(const _Tp* __lhs, const _Tp* __rhs, size_t __count) {
+#ifdef _LIBCPP_COMPILER_GCC
+  if (__libcpp_is_constant_evaluated()) {
+    for (; __count; --__count, ++__lhs, ++__rhs) {
+      if (*__lhs < *__rhs)
+        return -1;
+      if (*__rhs < *__lhs)
+        return 1;
+    }
+    return 0;
+  }
+#endif
+  return __builtin_memcmp(__lhs, __rhs, __count);
+}
+
+inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 const char*
+__constexpr_char_memchr(const char* __str, int __char, size_t __count) {
+#if __has_builtin(__builtin_char_memchr)
+  return __builtin_char_memchr(__str, __char, __count);
+#else
+  if (!__libcpp_is_constant_evaluated())
+    return static_cast<const char*>(std::memchr(__str, __char, __count));
+  for (; __count; --__count) {
+    if (*__str == __char)
+      return __str;
+    ++__str;
+  }
+  return nullptr;
+#endif
+}
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___STRING_CONSTEXPR_C_FUNCTIONS_H

libcxx/include/charconv

 #include <__debug>
 #include <__errc>
 #include <__memory/addressof.h>
 #include <__type_traits/make_32_64_or_128_bit.h>
 #include <__utility/unreachable.h>
 #include <cmath> // for log2f
 #include <cstdint>
 #include <cstdlib>
-#include <cstring>
 #include <limits>
 #include <type_traits>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
 _LIBCPP_PUSH_MACROS

 #endif // _LIBCPP_STD_VER > 14
 
 _LIBCPP_END_NAMESPACE_STD
 
 _LIBCPP_POP_MACROS
 
 #if !defined(_LIBCPP_REMOVE_TRANSITIVE_INCLUDES) && _LIBCPP_STD_VER <= 20
 #  include <concepts>
+#  include <cstring>
 #  include <iosfwd>
 #endif
 
 #endif // _LIBCPP_CHARCONV

libcxx/include/cstring

 using ::strrchr _LIBCPP_USING_IF_EXISTS;
 using ::strspn _LIBCPP_USING_IF_EXISTS;
 using ::strstr _LIBCPP_USING_IF_EXISTS;
 using ::strtok _LIBCPP_USING_IF_EXISTS;
 using ::memset _LIBCPP_USING_IF_EXISTS;
 using ::strerror _LIBCPP_USING_IF_EXISTS;
 using ::strlen _LIBCPP_USING_IF_EXISTS;
 
-inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 size_t __constexpr_strlen(const char* __str) {
-  // GCC currently doesn't support __builtin_strlen for heap-allocated memory during constant evaluation.
-  // https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70816
-#ifdef _LIBCPP_COMPILER_GCC
-  if (__libcpp_is_constant_evaluated()) {
-    size_t __i = 0;
-    for (; __str[__i] != '\0'; ++__i)
-      ;
-    return __i;
-  }
-#endif
-  return __builtin_strlen(__str);
-}
-
-template <class _Tp>
-_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 int
-__constexpr_memcmp(const _Tp* __lhs, const _Tp* __rhs, size_t __count) {
-#ifdef _LIBCPP_COMPILER_GCC
-  if (__libcpp_is_constant_evaluated()) {
-    for (; __count; --__count, ++__lhs, ++__rhs) {
-      if (*__lhs < *__rhs)
-        return -1;
-      if (*__rhs < *__lhs)
-        return 1;
-    }
-    return 0;
-  }
-#endif
-  return __builtin_memcmp(__lhs, __rhs, __count);
-}
-
-inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 const char*
-__constexpr_char_memchr(const char* __str, int __char, size_t __count) {
-#if __has_builtin(__builtin_char_memchr)
-  return __builtin_char_memchr(__str, __char, __count);
-#else
-  if (!__libcpp_is_constant_evaluated())
-    return static_cast<const char*>(std::memchr(__str, __char, __count));
-  for (; __count; --__count) {
-    if (*__str == __char)
-      return __str;
-    ++__str;
-  }
-  return nullptr;
-#endif
-}
-
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP_CSTRING

libcxx/include/fstream

 #include <__availability>
 #include <__config>
 #include <__locale>
 #include <__utility/move.h>
 #include <__utility/swap.h>
 #include <__utility/unreachable.h>
 #include <cstdio>
 #include <cstdlib>
-#include <cstring>
 #include <istream>
 #include <ostream>
 #include <typeinfo>
 #include <version>
 
 #if !defined(_LIBCPP_HAS_NO_FILESYSTEM_LIBRARY)
 #   include <filesystem>
 #endif

libcxx/include/list

 #include <__memory/pointer_traits.h>
 #include <__memory/swap_allocator.h>
 #include <__memory/unique_ptr.h>
 #include <__memory_resource/polymorphic_allocator.h>
 #include <__type_traits/is_allocator.h>
 #include <__utility/forward.h>
 #include <__utility/move.h>
 #include <__utility/swap.h>
-#include <cstring>
 #include <limits>
 #include <type_traits>
 #include <version>
 
 // standard-mandated includes
 
 // [iterator.range]
 #include <__iterator/access.h>

libcxx/include/module.modulemap.in

module streambuf {
     export *
   }
   module string {
     header "string"
     export initializer_list
     export string_view
     module __string {
       module char_traits           { private header "__string/char_traits.h" }
+      module constexpr_c_functions { private header "__string/constexpr_c_functions.h" }
       module extern_template_lists { private header "__string/extern_template_lists.h" }
       module string_fwd            { private header "__fwd/string.h" }
     }
     export *
   }
   module string_view {
     header "string_view"
     export initializer_list

libcxx/include/regex

 #include <__config>
 #include <__iterator/back_insert_iterator.h>
 #include <__iterator/wrap_iter.h>
 #include <__locale>
 #include <__memory_resource/polymorphic_allocator.h>
 #include <__utility/move.h>
 #include <__utility/pair.h>
 #include <__utility/swap.h>
-#include <cstring>
 #include <deque>
 #include <stdexcept>
 #include <string>
 #include <vector>
 #include <version>
 
 // standard-mandated includes
 

libcxx/include/string

 #include <__utility/auto_cast.h>
 #include <__utility/move.h>
 #include <__utility/swap.h>
 #include <__utility/unreachable.h>
 #include <climits>
 #include <cstdint>
 #include <cstdio>  // EOF
 #include <cstdlib>
-#include <cstring>
 #include <limits>
 #include <stdexcept>
 #include <string_view>
 #include <type_traits>
 #include <version>
 
 #ifndef _LIBCPP_HAS_NO_WIDE_CHARACTERS
 #  include <cwchar>

libcxx/include/vector

 #include <__type_traits/is_allocator.h>
 #include <__type_traits/noexcept_move_assign_container.h>
 #include <__utility/exception_guard.h>
 #include <__utility/forward.h>
 #include <__utility/move.h>
 #include <__utility/swap.h>
 #include <climits>
 #include <cstdlib>
-#include <cstring>
 #include <iosfwd> // for forward declaration of vector
 #include <limits>
 #include <stdexcept>
 #include <type_traits>
 #include <version>
 
 // standard-mandated includes
 

libcxx/src/include/ryu/common.h

 
 #ifndef _LIBCPP_SRC_INCLUDE_RYU_COMMON_H
 #define _LIBCPP_SRC_INCLUDE_RYU_COMMON_H
 
 // Avoid formatting to keep the changes with the original code minimal.
 // clang-format off
 
 #include <__assert>
-#include "__config"
+#include <__config>
+#include <cstring>
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI inline uint32_t __decimalLength9(const uint32_t __v) {
   // Function precondition: __v is not a 10-digit number.
   // (f2s: 9 digits are sufficient for round-tripping.)
   // (d2fixed: We print 9-digit blocks.)
   _LIBCPP_ASSERT(__v < 1000000000, "");

libcxx/test/libcxx/private_headers.verify.cpp

 #include <__ranges/take_while_view.h> // expected-error@*:* {{use of private header from outside its module: '__ranges/take_while_view.h'}}
 #include <__ranges/transform_view.h> // expected-error@*:* {{use of private header from outside its module: '__ranges/transform_view.h'}}
 #include <__ranges/view_interface.h> // expected-error@*:* {{use of private header from outside its module: '__ranges/view_interface.h'}}
 #include <__ranges/views.h> // expected-error@*:* {{use of private header from outside its module: '__ranges/views.h'}}
 #include <__ranges/zip_view.h> // expected-error@*:* {{use of private header from outside its module: '__ranges/zip_view.h'}}
 #include <__split_buffer> // expected-error@*:* {{use of private header from outside its module: '__split_buffer'}}
 #include <__std_stream> // expected-error@*:* {{use of private header from outside its module: '__std_stream'}}
 #include <__string/char_traits.h> // expected-error@*:* {{use of private header from outside its module: '__string/char_traits.h'}}
+#include <__string/constexpr_c_functions.h> // expected-error@*:* {{use of private header from outside its module: '__string/constexpr_c_functions.h'}}
 #include <__string/extern_template_lists.h> // expected-error@*:* {{use of private header from outside its module: '__string/extern_template_lists.h'}}
 #include <__thread/poll_with_backoff.h> // expected-error@*:* {{use of private header from outside its module: '__thread/poll_with_backoff.h'}}
 #include <__thread/timed_backoff_policy.h> // expected-error@*:* {{use of private header from outside its module: '__thread/timed_backoff_policy.h'}}
 #include <__tuple_dir/apply_cv.h> // expected-error@*:* {{use of private header from outside its module: '__tuple_dir/apply_cv.h'}}
 #include <__tuple_dir/make_tuple_types.h> // expected-error@*:* {{use of private header from outside its module: '__tuple_dir/make_tuple_types.h'}}
 #include <__tuple_dir/pair_like.h> // expected-error@*:* {{use of private header from outside its module: '__tuple_dir/pair_like.h'}}
 #include <__tuple_dir/sfinae_helpers.h> // expected-error@*:* {{use of private header from outside its module: '__tuple_dir/sfinae_helpers.h'}}
 #include <__tuple_dir/tuple_element.h> // expected-error@*:* {{use of private header from outside its module: '__tuple_dir/tuple_element.h'}}

libcxx/test/libcxx/strings/c.strings/constexpr.cstring.compile.pass.cpp

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 // UNSUPPORTED: c++03, c++11
 
+// ADDITIONAL_COMPILE_FLAGS: -Wno-private-header
+
 // Check that __constexpr_* cstring functions are actually constexpr
 
-#include <cstring>
+#include <__string/constexpr_c_functions.h>
 
 static_assert(std::__constexpr_strlen("Banane") == 6, "");
 static_assert(std::__constexpr_memcmp("Banane", "Banand", 6) == 1, "");
 static_assert(std::__constexpr_memcmp("Banane", "Banane", 6) == 0, "");
 static_assert(std::__constexpr_memcmp("Banane", "Bananf", 6) == -1, "");
 
 constexpr bool test_constexpr_wmemchr() {
   const char str[] = "Banane";
   return std::__constexpr_char_memchr(str, 'n', 6) == str + 2;
 }
 static_assert(test_constexpr_wmemchr(), "");

libcxx/test/libcxx/transitive_includes/cxx03.csv

 filesystem type_traits
 filesystem version
 format array
 format bit
 format charconv
 format cstddef
 format cstdint
 format cstdlib
-format cstring
 format initializer_list
 format limits
 format locale
 format optional
 format queue
 format stack
 format stdexcept
 format string

libcxx/test/libcxx/transitive_includes/cxx11.csv

 filesystem type_traits
 filesystem version
 format array
 format bit
 format charconv
 format cstddef
 format cstdint
 format cstdlib
-format cstring
 format initializer_list
 format limits
 format locale
 format optional
 format queue
 format stack
 format stdexcept
 format string

libcxx/test/libcxx/transitive_includes/cxx14.csv

 filesystem type_traits
 filesystem version
 format array
 format bit
 format charconv
 format cstddef
 format cstdint
 format cstdlib
-format cstring
 format initializer_list
 format limits
 format locale
 format optional
 format queue
 format stack
 format stdexcept
 format string

libcxx/test/libcxx/transitive_includes/cxx17.csv

 filesystem type_traits
 filesystem version
 format array
 format bit
 format charconv
 format cstddef
 format cstdint
 format cstdlib
-format cstring
 format initializer_list
 format limits
 format locale
 format optional
 format queue
 format stack
 format stdexcept
 format string

libcxx/test/libcxx/transitive_includes/cxx20.csv

 filesystem type_traits
 filesystem version
 format array
 format bit
 format charconv
 format cstddef
 format cstdint
 format cstdlib
-format cstring
 format initializer_list
 format limits
 format locale
 format optional
 format queue
 format stack
 format stdexcept
 format string

libcxx/test/libcxx/transitive_includes/cxx2b.csv

 bitset type_traits
 bitset version
 ccomplex complex
 charconv cerrno
 charconv cmath
 charconv cstddef
 charconv cstdint
 charconv cstdlib
-charconv cstring
 charconv initializer_list
 charconv limits
 charconv type_traits
 chrono array
 chrono bit
 chrono charconv
 chrono cmath
 chrono compare
 chrono cstddef
 chrono cstdint
 chrono cstdlib
-chrono cstring
 chrono ctime
 chrono initializer_list
 chrono limits
 chrono locale
 chrono optional
 chrono ostream
 chrono ratio
 chrono sstream

 filesystem type_traits
 filesystem version
 format array
 format bit
 format charconv
 format cstddef
 format cstdint
 format cstdlib
-format cstring
 format initializer_list
 format limits
 format locale
 format optional
 format queue
 format stack
 format stdexcept
 format string