[libc++][Modules] Remove unnecessary `requires` from the module map

[iana]

Summary

Top level modules don't need requires because they're only built when their headers are included.

[iana]

For background, requires is generally used like this.

module ABC {
  header "plain.h"
  module NeedsCPP {
    requires cplusplus
    header "needs_cpp.hpp"
  }
}

Building ABC would normally precompile both headers, but with the requires in place, needs_cpp.hpp will be skipped if the module is built in pure C mode. If NeedsCPP is a top level module, the requires isn't necessary anymore and dirties up the module map. In the libc++ case, not all the requires are even accurate, some of the headers are include-able without the feature. e.g. stdatomic.h doesn't actually require C++23, it will #include_next in earlier versions and still be buildable. I found that out while testing D157364 but figured this deserved its own review.

[Mordante]

Are you sure they are not needed? In the previous version of the module map I had to add them. I see the modular build failing too. I really want to see it green.

[iana]

In D157363#4570306, @Mordante wrote:

Are you sure they are not needed? In the previous version of the module map I had to add them. I see the modular build failing too. I really want to see it green.

Trying to figure out why the modular build is failing, doesn't look related but I need to check it out.

home/libcxx-builder/.buildkite-agent/builds/google-libcxx-builder-8997ed9990e4-1/llvm-project/libcxx-ci/build/generic-modules/include/c++/v1/__algorithm/pstl_backends/cpu_backends/for_each.h:52:10: error: no member named 'for_each' in namespace 'std'; did you mean 'for_each'?

 52 |     std::for_each(__first, __last, __func);

    |     ~~~~~^

home/libcxx-builder/.buildkite-agent/builds/google-libcxx-builder-8997ed9990e4-1/llvm-project/libcxx-ci/build/generic-modules/include/c++/v1/__algorithm/for_each.h:22:74: note: 'for_each' declared here

 22 | inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX20 _Function for_each(_InputIterator __first,

    |                                                                          ^

[iana]

In D157363#4570479, @iana wrote:

In D157363#4570306, @Mordante wrote:

Are you sure they are not needed? In the previous version of the module map I had to add them. I see the modular build failing too. I really want to see it green.

Trying to figure out why the modular build is failing, doesn't look related but I need to check it out.

Looks like that was a transient failure, all that's left is the (I think known) AIX failures.

[iana]

Rebase

[Mordante]

LGTM, but I like @ldionne to have a look at this too.
I assume we don't need to backport this patch to LLVM-17. Is that correct?

[iana]

In D157363#4577404, @Mordante wrote:

LGTM, but I like @ldionne to have a look at this too.
I assume we don't need to backport this patch to LLVM-17. Is that correct?

I'm not really sure. If we want D157364 for v17 because it adds things back to the std module that we removed, then we'll need this too.

[Mordante]

In D157363#4578121, @iana wrote:

In D157363#4577404, @Mordante wrote:

LGTM, but I like @ldionne to have a look at this too.
I assume we don't need to backport this patch to LLVM-17. Is that correct?

I'm not really sure. If we want D157364 for v17 because it adds things back to the std module that we removed, then we'll need this too.

We backported the hard-coded __std_clang_module header to LLVM 17.
We'll never add new headers to LLVM 17 so we don't need to backport the __std_clang_module header generator script.

Does that answer your question? If not maybe reach out on Discord.

[iana]

In D157363#4580570, @Mordante wrote:

In D157363#4578121, @iana wrote:

In D157363#4577404, @Mordante wrote:

LGTM, but I like @ldionne to have a look at this too.
I assume we don't need to backport this patch to LLVM-17. Is that correct?

I'm not really sure. If we want D157364 for v17 because it adds things back to the std module that we removed, then we'll need this too.

We backported the hard-coded __std_clang_module header to LLVM 17.
We'll never add new headers to LLVM 17 so we don't need to backport the __std_clang_module header generator script.

Does that answer your question? If not maybe reach out on Discord.

We did, but the hard coded __std_clang_module header didn't include as much things as the previous std module did since it put so many headers behind unnecessary macro guards. Maybe that's not a big deal.

[ldionne]

This makes sense to me, we had talked about doing this when we reviewed @iana 's original modulemap patch. The CI failure is only AIX, which is known to fail right now, so this LGTM.

However, we should be updating the LIBCXX_CONFIGURED_WITHOUT_SUPPORT_FOR_THIS_HEADER stuff in CMakeLists.txt as well.

[iana]

In D157363#4581359, @ldionne wrote:

This makes sense to me, we had talked about doing this when we reviewed @iana 's original modulemap patch. The CI failure is only AIX, which is known to fail right now, so this LGTM.

However, we should be updating the LIBCXX_CONFIGURED_WITHOUT_SUPPORT_FOR_THIS_HEADER stuff in CMakeLists.txt as well.

I left the LIBCXX_CONFIGURED_WITHOUT_SUPPORT_FOR_THIS_HEADER stuff in CMakeLists.txt because the experimental headers are all still in a single module, so they still use LIBCXX_ENABLE_LOCALIZATION. I could get rid of the other ones, but I thought it was best to leave them all in case other experimental headers use other ones. Also if we go back to grouping private headers together, we'll need some more requires.

[ldionne]

LGTM. CI issue is AIX, so everything is green.

libcxx/include/module.modulemap.in

module std_array [system] {
   header "array"
   export *
 }
 module std_atomic [system] {
   header "atomic"
   export *
 }
 module std_barrier [system] {
-  @requires_LIBCXX_ENABLE_THREADS@
   header "barrier"
   export *
 }
 module std_bit [system] {
   header "bit"
   export *
 }
 module std_bitset [system] {
   header "bitset"
   export *
 }
 module std_charconv [system] {
   header "charconv"
   export *
 }
 module std_chrono [system] {
   header "chrono"
   export *
 }
 module std_codecvt [system] {
-  @requires_LIBCXX_ENABLE_LOCALIZATION@
   header "codecvt"
   export *
 }
 module std_compare [system] {
   header "compare"
   export *
 }
 module std_complex [system] {
module std_execution [system] {
   header "execution"
   export *
 }
 module std_expected [system] {
   header "expected"
   export *
 }
 module std_filesystem [system] {
-  @requires_LIBCXX_ENABLE_FILESYSTEM@
   header "filesystem"
   export *
 }
 module std_format [system] {
   header "format"
   export *
 }
 module std_forward_list [system] {
   header "forward_list"
   export *
 }
 module std_fstream [system] {
-  @requires_LIBCXX_ENABLE_LOCALIZATION@
-  @requires_LIBCXX_ENABLE_FILESYSTEM@
   header "fstream"
   export *
 }
 module std_functional [system] {
   header "functional"
   export *
 }
 module std_future [system] {
-  @requires_LIBCXX_ENABLE_THREADS@
   header "future"
   export *
 }
 module std_initializer_list [system] {
   header "initializer_list"
   export *
 }
 module std_iomanip [system] {
-  @requires_LIBCXX_ENABLE_LOCALIZATION@
   header "iomanip"
   export *
 }
 module std_ios [system] {
-  @requires_LIBCXX_ENABLE_LOCALIZATION@
   header "ios"
   export *
 }
 module std_iosfwd [system] {
   header "iosfwd"
   export *
 }
 module std_iostream [system] {
-  @requires_LIBCXX_ENABLE_LOCALIZATION@
   header "iostream"
   export *
 }
 module std_istream [system] {
-  @requires_LIBCXX_ENABLE_LOCALIZATION@
   header "istream"
   export *
 }
 module std_iterator [system] {
   header "iterator"
   export *
 }
 module std_latch [system] {
-  @requires_LIBCXX_ENABLE_THREADS@
   header "latch"
   export *
 }
 module std_limits [system] {
   header "limits"
   export *
 }
 module std_list [system] {
   header "list"
   export *
 }
 module std_locale [system] {
-  @requires_LIBCXX_ENABLE_LOCALIZATION@
   header "locale"
   export *
 }
 module std_map [system] {
   header "map"
   export *
 }
 module std_mdspan [system] {
module std_numeric [system] {
   header "numeric"
   export *
 }
 module std_optional [system] {
   header "optional"
   export *
 }
 module std_ostream [system] {
-  @requires_LIBCXX_ENABLE_LOCALIZATION@
   header "ostream"
   export *
 }
 module std_print [system] {
   header "print"
   export *
 }
 module std_queue [system] {
   header "queue"
   export *
 }
 module std_random [system] {
   header "random"
   export *
 }
 module std_ranges [system] {
   header "ranges"
   export *
 }
 module std_ratio [system] {
   header "ratio"
   export *
 }
 module std_regex [system] {
-  @requires_LIBCXX_ENABLE_LOCALIZATION@
   header "regex"
   export *
 }
 module std_scoped_allocator [system] {
   header "scoped_allocator"
   export *
 }
 module std_semaphore [system] {
-  @requires_LIBCXX_ENABLE_THREADS@
   header "semaphore"
   export *
 }
 module std_set [system] {
   header "set"
   export *
 }
 module std_shared_mutex [system] {
-  @requires_LIBCXX_ENABLE_THREADS@
   header "shared_mutex"
   export std_version
 }
 module std_source_location [system] {
   header "source_location"
   export *
 }
 module std_span [system] {
   header "span"
   export std_private_ranges_enable_borrowed_range
   export std_version
   export std_private_span_span_fwd
 }
 module std_sstream [system] {
-  @requires_LIBCXX_ENABLE_LOCALIZATION@
   header "sstream"
   export *
 }
 module std_stack [system] {
   header "stack"
   export *
 }
 module std_stdexcept [system] {
   header "stdexcept"
   export *
 }
 module std_stop_token {
-  @requires_LIBCXX_ENABLE_THREADS@
   header "stop_token"
   export *
 }
 module std_streambuf [system] {
-  @requires_LIBCXX_ENABLE_LOCALIZATION@
   header "streambuf"
   export *
 }
 module std_string [system] {
   header "string"
   export *
 }
 module std_string_view [system] {
   header "string_view"
   export *
 }
 module std_strstream [system] {
-  @requires_LIBCXX_ENABLE_LOCALIZATION@
   header "strstream"
   export *
 }
 module std_system_error [system] {
   header "system_error"
   export *
 }
 module std_thread [system] {
-  @requires_LIBCXX_ENABLE_THREADS@
   header "thread"
   export *
 }
 module std_tuple [system] {
   header "tuple"
   export *
 }
 module std_type_traits [system] {
module std_ciso646 [system] {
   header "ciso646"
   export *
 }
 module std_climits [system] {
   header "climits"
   export *
 }
 module std_clocale [system] {
-  @requires_LIBCXX_ENABLE_LOCALIZATION@
   header "clocale"
   export *
 }
 module std_cmath [system] {
   header "cmath"
   export *
 }
 module std_csetjmp [system] {
module std_ctime [system] {
   header "ctime"
   export *
 }
 module std_cuchar [system] {
   header "cuchar"
   export *
 }
 module std_cwchar [system] {
-  @requires_LIBCXX_ENABLE_WIDE_CHARACTERS@
   header "cwchar"
   export *
 }
 module std_cwctype [system] {
-  @requires_LIBCXX_ENABLE_WIDE_CHARACTERS@
   header "cwctype"
   export *
 }
 
 // C standard library interfaces augmented/replaced in C++
 // <assert.h> provided by C library.
 module std_complex_h [system] {
   header "complex.h"
module std_inttypes_h [system] {
   export *
 }
 // <iso646.h> provided by compiler.
 module std_limits_h [system] {
   header "limits.h"
   export *
 }
 module std_locale_h [system] {
-  @requires_LIBCXX_ENABLE_LOCALIZATION@
   header "locale.h"
   export *
 }
 module std_math_h [system] {
   header "math.h"
   export *
 }
 module std_setjmp_h [system] {
   header "setjmp.h"
   export *
 }
 // <signal.h> provided by C library.
 // FIXME: <stdalign.h> is missing.
 // <stdarg.h> provided by compiler.
 module std_stdatomic_h [system] {
-  @requires_LIBCXX_ENABLE_THREADS@
-  requires cplusplus23
   header "stdatomic.h"
   export *
 }
 module std_stdbool_h [system] {
   // <stdbool.h>'s __bool_true_false_are_defined macro requires textual inclusion.
   textual header "stdbool.h"
   export *
 }
module std_tgmath_h [system] {
   export *
 }
 module std_uchar_h [system] {
   header "uchar.h"
   export *
 }
 // <time.h> provided by C library.
 module std_wchar_h [system] {
-  @requires_LIBCXX_ENABLE_WIDE_CHARACTERS@
   // <wchar.h>'s __need_* macros require textual inclusion.
   textual header "wchar.h"
   export *
 }
 module std_wctype_h [system] {
-  @requires_LIBCXX_ENABLE_WIDE_CHARACTERS@
   header "wctype.h"
   export *
 }
 
 // Experimental C++ standard library interfaces
 module std_experimental [system] {
-  requires cplusplus11
-
   module deque {
     header "experimental/deque"
     export *
   }
   module forward_list {
     header "experimental/forward_list"
     export *
   }
module std_private_config            [system] {
   textual header "__config"
   export *
 }
 module std_private_hash_table        [system] {
   header "__hash_table"
   export *
 }
 module std_private_locale            [system] {
-  @requires_LIBCXX_ENABLE_LOCALIZATION@
   header "__locale"
   export *
 }
 module std_private_mbstate_t         [system] {
   header "__mbstate_t.h"
   export *
 }
 module std_private_node_handle       [system] {

 module std_private_chrono_convert_to_tm          [system] { header "__chrono/convert_to_tm.h" }
 module std_private_chrono_day                    [system] { header "__chrono/day.h" }
 module std_private_chrono_duration               [system] {
   header "__chrono/duration.h"
   export std_private_type_traits_is_convertible
 }
 module std_private_chrono_file_clock             [system] { header "__chrono/file_clock.h" }
 module std_private_chrono_formatter              [system] {
-  @requires_LIBCXX_ENABLE_LOCALIZATION@
   header "__chrono/formatter.h"
 }
 module std_private_chrono_hh_mm_ss               [system] { header "__chrono/hh_mm_ss.h" }
 module std_private_chrono_high_resolution_clock  [system] {
   header "__chrono/high_resolution_clock.h"
   export std_private_chrono_steady_clock
   export std_private_chrono_system_clock
 }
 module std_private_chrono_literals               [system] { header "__chrono/literals.h" }
 module std_private_chrono_month                  [system] { header "__chrono/month.h" }
 module std_private_chrono_month_weekday          [system] { header "__chrono/month_weekday.h" }
 module std_private_chrono_monthday               [system] { header "__chrono/monthday.h" }
 module std_private_chrono_ostream                [system] {
-  @requires_LIBCXX_ENABLE_LOCALIZATION@
   header "__chrono/ostream.h"
 }
 module std_private_chrono_parser_std_format_spec [system] {
-  @requires_LIBCXX_ENABLE_LOCALIZATION@
   header "__chrono/parser_std_format_spec.h"
 }
 module std_private_chrono_statically_widen       [system] { header "__chrono/statically_widen.h" }
 module std_private_chrono_steady_clock           [system] {
   header "__chrono/steady_clock.h"
   export std_private_chrono_time_point
 }
 module std_private_chrono_system_clock           [system] {

 module std_private_ranges_enable_view                [system] { header "__ranges/enable_view.h" }
 module std_private_ranges_filter_view                [system] {
   header "__ranges/filter_view.h"
   export std_private_ranges_range_adaptor
 }
 module std_private_ranges_from_range                 [system] { header "__ranges/from_range.h" }
 module std_private_ranges_iota_view                  [system] { header "__ranges/iota_view.h" }
 module std_private_ranges_istream_view               [system] {
-  @requires_LIBCXX_ENABLE_LOCALIZATION@
   header "__ranges/istream_view.h"
 }
 module std_private_ranges_join_view                  [system] {
   header "__ranges/join_view.h"
   export std_private_iterator_iterator_with_data
   export std_private_iterator_segmented_iterator
 }
 module std_private_ranges_lazy_split_view            [system] {